Saturday, March 31, 2018
What is meant by good acoustics?
If it is meant good acoustics for recording...
Then perhaps what it means is low quantity of first reflections.
When we make a recording in an ordinary room it usually sounds very bad. The reason why seems to be that we have first reflections 2 times. One while recording and again while reproducing in a similar room.
In a big room first reflections are delayed.
And an infinite room must be nice too, the time for first reflection to come back is infinite.
Perhaps this is why outdoors sound so nice and clear. And the sound of a quiet beach or forest must be paradise.
On big rooms the mic can be further from the source and omnidirectional mics are appropriate at larger distances too.
Smaller rooms can benefit from absorbers. But not only the usual porous absorbers for high frequencies. Wood panels, elastomer panels or membranes are needed to covert low frequencies to heat by sympathetic vibration. (See BBC, EMI absorbers). An example of material is linoleum.
How Breakfast at Tiffany's - Mancini has been recorded?
The sound engineer Al Shmitt loves omnidirectional mics and uses leakage constructively as can be read and seen on YouTube on numerous interviews.
Another interesting interview on YouTube is Frank Laico discussing how he recorded in the church converted studio for Columbia in New York.
And the book Making Records, the scenes behind the music - Phil Ramone has some description of what Phil Ramone did for acoustics at A&R studios.
Bubliography:
Acoustics of radio and television studios - Guilford - BBC
Studio Acoustics - Rettinger
Microphones - Robertson - BBC
The master handbook of acoustics - Everest
Microphones - Boré, Peus - Neumann
AKG D 1000 E and Pleiades V6
Signal path, setup:
AKG D 1000 E - Pleiades V6 - Sony TC-D5 Pro - Sennheiser HD 580
It sounded great.
But only when the low cut of the mic was on.
When the mic was at position B and the low cut was done by the Input transformer of the V6 there was an unfocused mid bass haziness that reminded what happened when the Sennheiser MD441 U3 (the version without low cut option) was connected to the V6.
Then it was decided to insert Pleiades filters between the mic and V6.
Again the sound left something to be desired and the internal low cut of the D1000 made a much better job.
So it seems that although Pleiades filters do a great job of removing all that bass heaviness due to proximity effect the core must be somehow overload by such a great excitation current.
The BBC 1:18 transformer described on the MD441 U3 to V6 post was also connected between D1000 and TC-D5. There was proximity compensation because of the low primary inductance. The sound was nice but still the mid bass was fuzzy. Possible core saturation?
The filter inside the AKG is implemented in a great way. Is it the core material used. The resistance of the winding? A series see sister with the winding?
By looking at the D-1000 data sheet there is a series resistor with an inductor for the M(medium) position. For the S (Sharp) position there is an other resistor in series with an inductor in parallel with a capacitor combination.
Pleiades filters may need to be improved.
On omnidirectional mics the sound is almost already there as there is no proximity effect. This possibly explains why they are so clear on vocals.
Can one become fair with directional mics?
Does a 30 milliwatt amplifier sound loud?
Yes it can sound loud.
Why?
The ear has a dynamic range of 120dB, or 120deciBels or 12 Bels.
This means it can cope with power change ratios of 12 zeros. Ie a power ratio of a million million.
So just 3 zeros is a walk in the park.
A 30W amplifier will not sound all that much louder than 30mW.
And if the 30mW comes from a class A operating device (electrons flowing all the time) it will sound loud and very natural due to linearity and smoothness at low levels and progressive non linearity (loud subjectively) at peaks. See reference.
As of writing this an Antonio Carlos Jobim CD is playing through the following system.
Signal path, setup:
Jobim Jazz masters 13, Verve - Sony CD Walkman D-EJ758CK (line out) - Pleiades 2N3053 a few milliwatt power amplifier supplied by 12V, 65mA - Philips AD5046N
The sound quality is jaw dropping.
Just one transistor from source to a directly connected to collector 800Ω speaker.
After listening to so many systems, this one makes one feel so happy.
How funny is it. This circuit is always in front of us. Hidden by its simplicity. So one is perhaps reluctant to try it.
It's the first circuit we think we learn. The first circuit we see in all the great electronics books such as Electronic Engineering - Terman.
Life is nice.
References:
Tubes vs Trasistors (vs op amps), Is there an audible difference - Russel O. Hamm - Journal of the Audio Engineering Society
Electronic Engineering - Terman
Madonna's Voice Coming from a Point Source - euroelectron
Friday, March 30, 2018
Why changing the impedance all the time?
Sound production and reproduction from producers brain to listener's brain may involve a microphone near the input and a loudspeaker near the output.
If Bono sings in the studio with an SM58 the voice coil is typically 25Ω or near to let's say 8Ω.
Then at the other end of the listener there is very usually a speaker of 8Ω.
But in between these, the signal is not left alone. We change its impedance all the time.
The 25Ω is stepped by an internal mic transformer to 200Ω.
200Ω is set down the line and then is stepped up again to a higher impedance by a studio signal transformer to drive an electron tube grid, or the gate of a JFET.
And there are again transformations perhaps to lower impedance to drive transistors.
And then at the listener's end if an electron tube power amplifier is used again a high impedance is changed by a trasformer to low impedance to drive the 8Ω voicecoil.
Could we just use a darlighton current amplification stage and drive directly from a microphone voice coil the voice coil of a loudspeaker?
There may be noise considerations but who knows?
We could also step up a great 25Ω mic such as a Grampian DP4/L to just 2.5KΩ and drive a low noise electron tube booster preamplifier such as Pleiadss V6. And then perhaps add some more stages and drive a high impedance voice coil speaker.
These are nice experiments. And it should sound great? one mic used in a room and a loudspeaker directly resproducing in another room. Just linked by a cable.
But why not having a listener next to us while playing the piano or the guitar?
Or a singer sing to us directly to our ears?
Or our sweetheart on a quiet beach singing to us, to herself?
We have lost paradise just by choice.
We have the freewill getting it back.
Ιςως ο καλύτερος τρόπος να καταρρίψεις τα επιχειρήματα κάποιου ειναι να συμφωνήσεις μαζι του
Βιβλιογραφία:
Πως να αποκτήσετε φίλους και να επηρεάσετε το περιβάλλον σας - Ντέιλ Καρνεγκυ
Are 800ohm or hi impedance speakers desirable?
Possibly yes.
They are not current hungry.
(Neither too voltage hungry, around 600Ω is neither too high or too low impedance.)
Bipolar transistors are current gain devices.
So just a transistor can be used to drive a 800Ω speaker directly from a CD line output.
An example signal path:
Sony D-EJ758CK - 2N3053 operating in class A - Philips AD5046N directly connected to the collector.
Also the collector current, thereby the battery supply current is low which is good news for battery operating time.
The above setup can operate with a 9V battery.
How about 10KΩ voice coils so that direct electron tube anode connection is possible. Or how about a low impedance triode 6A3 etc to a 800Ω voicecoil? Or perhaps lowering the impedance of electron tubes at low voltage by a high Megohm anode to grid resistor as on the Pleiades V6. (Any voltage can be dangerous. At your risk, all safety precautions should be strictly followed).
Another advantage is that the speaker cable can be thin.
Very simple class A operating amplifiers can be designed around hi Z speakers.
On the above example the power consumption and power output is very low. Typically 60mW consumption. 30mW of music.
Yet the sound quality is prestine and the sound level acceptable.
Why?
Possibly because of the logarithmic response of the ear brain to sound intensity. By the way these amps are great for learning to sing as low intesities make the human brain to perceive the correct pitch.
And to the fact that most music is on the average around the zero crossing point. A place where class A amplifiers (electrons flowing all the time) excell.
At peaks there is gradual distortion. Many systems of nature are non linear at large signals and linear at small. The ear brain is no exception. The loud signals which of course are limited by the non linearity of the amp and the brain ear is fooled that something loud is there.
Bibliography:
Sound and Hearing - Smith, Warshofsky - Time Life science series
Tubes bs Transistors is there an obvious difference? - Russel O. Hamm - JAES
Electronics, a systems approach - Neil Storey
Operating a power amplifier with just a 9V battery
See the next euroelectron posts.
The amplifier is just a 2N3053 bipolar transistor operating in class A.
The speaker is the Philips AD5046N, 800Ω.
Current consumption is only 6mA with the current bias resistor used from collector to base.
As of writing this the song Little Star - Madonna plays on CD.
The sound quality is excellent.
Excellent bass, middle and treble frequency information.
And this Philips speaker may possibly be the best ever used on Pleiades experiments.
Voltage drop at the battery terminals is minimal about 200mV.
Some distortion becomes now obvious as the 9.6V NiMh rechargeable battery has discharged from 10.4V to 8.5V.
Thursday, March 29, 2018
Improvements to the Pleiades one transistor power amplifier
On the next euroelectron post with title:
Madonna's voice coming from a point source.
http://euroelectron.blogspot.gr/2018/03/madonnas-voice-coming-from-point-source.html
Madonna's voice coming from a point source
At your own risk. Take all safety precautions even when experimenting with low voltage.
This is on using just one transistor to drive directly a loudspeaker.
_____________________________
| | 2N3053 |
73KΩ [] | c |
in ----==-----------|--------- b < 800Ω [ ]<
4K7 | e |
______________________|________. |_________| |^| 6.5mA
' | 10.3V
The Pleiades 2N3053 power amplifier schematic (73KΩ is a typical value, Rcb is adjusted by ear-brain)
Pleiades experiments with the 2N3055 driving directly an 8ohm voice coil have been previously described.
This is on driving a 800Ω Philips AD5046N full range speaker.
Before attempting to drive this speaker with a triode electron tube such as an WE417, 6C4, triode connected EF183, for example it was desired to try a transistor. This has the advantage of no heater voltage which is important for an amplifier designed to operate from a battery and still be class A. Class A means electrons flowing all the time.
The 2N3055 experiments gave a fine sound. The problem is impedance mismatching making an amplifier that consumes 100-200mA but does not sound as loud as it should. And when a 9V battery is used only a few songs can be played before the battery is discharged.
The 2N3055 would have prefered to see a load of 80Ω instead of 8Ω. In fact supplying with 12V, only 1 or 2 volts are dropped in the speaker. (The speaker is directly connected to the collector on these experiments, so electrons flow all the time through the speaker too, the cone can be seen to be somewhat deflected to a new equilibrium).
A speaker of 800Ω is good news and there are many transistors that can be seen in old germanium datebooks to drive 600Ω.
However when the drawers were opened a nice transistor on a round heat sink caught the attention of the eye immediately. It is a 2N3053. And it's datasheet shows good news. Current about 30mA. The impedance seems to be very close to the speaker.
So by impedance matching an efficient transfer of energy without reflecting back will take place.
It was tried and yes it works beautifully. And the current consumption is about 10 times less while the sound is as loud. And it is louder, as the Philips with its AlNiCo magnet is more efficient and sounds louder.
The sound is amazing. While writing this Madonna can be heard coming from a point source as clear and smooth.
Signal path, setup:
To Have and Not to Hold - Madonna - Sony D-EJ758CK CD Walkman at its 300Ω line out impedance - a series resistor of 4.7KΩ - 2N3053 with 73ΚΩ bias resistor from collector to base - Philips AD5046N connected to collector, 12 V power supply, emitter connected to minus or gnd
More batteries in series were also tried for louder sound so the best conditions (using a variable bias resistor while listening) are as follows:
Vb=36V, Ic=21mA, Rcb=120KΩ
Vb=24V, Ic=14mA
Vb=10.3V, Ic=6.5mA, Rcb=73KΩ, Vc=5.8V
It is nice that the voltage is now shared and that about half of Vb appears at the collector as about half drops through the voice coil itself.
Power consumption is very low now by a current as low as just 6.5mA. Strictly speaking power is voltage times current. The sound is world class with just one transistor and 2 resistors from source to speaker.
It is nice that now most of the power input is not converted to heat, (the 2N3055 got hot), but much of the power is converted to music. To calculate power the P=VxI relation is used. The power input is 10.3Vx6.5mA=67mW. The power desipation at the transistor is 5.8Vx6.5mA=37mW. The rest of power (10.3V-5.8V)x6.5mA=30mW is desipated at the speaker voice coil. Of course when signal exists the transistor cools down. The voice coil moves and radiates acoustic power etc. For an excellent description of power desipation in class A circuits see T.S. Gray.
The Pleiades power amplifier is based on the circuit presented by Jones. And the attempt of course is to further simplify it by removing as much components as possible!
So how does it sound like?
At the moment the least power version was chosen as it sounds very nice. The sound is smooth. With amazing midrange. Extended treble but not hyped, not harsh at all. And great bass as the amp being direct coupled goes down to as close to 0 Hz as possible. The almost 0Hz component can be seen by the permanent deflection of the cone.
At peaks there is of course some clipping, soft clipping distortion. But it is the kind of distortion that mastering studios charge many hundreds of dollars per hour to put into the final product by class A operating electron tube amplifiers, Fairchild compressors etc.
It is great that Madonna comes from a single point in space in this mono arrangement. It is close to her being in the room at some point in space.
The amplifier is enough loud to listen to great quality music and being able to keep a conversation.
And nobody will tell you to turn it down.
How could the electron tube version sound like?
The electron tube's anode can be connected directly to the 800Ω voice coil. Rk can be variable for max gain and best sound quality. Or cathode connected to gnd and high Megohm anode to grid resistor may make operation of the electron tube at a relatively low anode voltage. (See Pleiades V4, V5, V6 for example). This electron freeing resistor conserves the value of Gm. Since μ is dictated by the geometry of the tube it follows that ra will be lower. Or since we can have high Ia with low Va this means we have a lower Ra or electron tube output resistance. With a WE417A it should be possible to have an Ra of 800Ω, if this is so it will be a perfect match in terms of max power transfer to the 800Ω voice coil.
References:
2 Transistor Miniature A.F. Amplifier by K. Jones - page 41 - Audio Amplifiers - Edited by J. R. Davies - Data Publications Ltd - London
Applied Electronics - T.S. Gray - MIT
On Preserving Electron Tube Transconductance at Low Anode Potential - euroelectron
Tubes vs Transistors (vs op amps), Is there an audible difference? - Russel O. Hamm - Journal of the Audio Engineering Society
Wednesday, March 28, 2018
By observing the very young, the elderly and intelligent animals there is so much to learn
For example the young may say everybody has love, and it is true.
The elderly may swim even in winter and they are in great health.
By observing cats for example so much can be learned, from hygiene practice to flirting.
The Point Source
So many times have we seen elderly people with a transistor radio close to them.
While writting this post a CD is listened to with just one speaker (see next euroelectron post).
The speaker is a vintage Philips non open back, the Philips AD 5046N. The intelligibility even in a reverberant tilled kitchen is amazing. Can't wait for the CD to finish and then play Ray of Light - Madonna.
Ah, those radios. They are a point source. A physical entity.
Listening to mono signals with one speaker
It makes sense.
It sounds amazing.
By reading a bit about Jeff Emerick the impression is that mono teaches you to have everything perfect so that it sounds so on just one speaker.
By reading a bit about Joe Meek, he advices to listen a mono mix from one only speaker.
By reading a bit about Phil Spector, he is strongly into mono.
Modern recordings sound great too when the L and R voltage signals are summed and sent to a single speaker.
Another example of fabulous sound is a mono radio with its single speaker.
As of writing this post a CD Walkman plays Dionne Warwick. The headphone out is bridged, L and R are connected together. They feed a small military transformer to step up from 8Ω to 600Ω. An 800Ω Philips full range speaker is then connected. Very interesting sound.
Setup, signal path
Sony CD Walkman from headphone out - 8Ω:600Ω transformer - Philips AD5046N (9710 AM drive unit)
How would this speaker sound with a WE417 triode directly connected to the anode? Should a circuit similar to Pleiades V6 be used with lower anode voltage? (Attention to any voltage, all safety precautions should be observed, your own risk).
References:
Behind the Glass (chapter on Jeff Emerick) - Howard Massey
Recording Iconoclast Joe Meek heard a new world - Electronic Musician
Rock and Roll; In the Groove - Interview with Larry Levine
http://openvault.wgbh.org/catalog/V_789E40077C6F49268E4579EB7FA8E888
Tuesday, March 27, 2018
Great information on the Neumann M49, M50
http://recordinghacks.com/microphones/Neumann/M-50
http://recordinghacks.com/pdf/neumann/M49-M50.pdf
Did Al Schmitt use the M50 on Breakfast at Tiffany's?
Reducing treble after the MD21 or MD421
These are world class Sennheiser microphones.
If used for close intimate vocals and the sound is bass heavy Pleiades filters or other techniques (see for example the next electron post which has not been tried) may be used.
But what if the sound is treble heavy too to listener's brain.
A very nice gentle high cut can be made by connecting a small capacitor across the anode. Or a capacitor in series with a resistor or in series with a variable resistor. A technique used on electron tube vintage record players such as Dansette etc.
So a signal path can be:
Mic - Pleiades V6 with and added variable high cut at the anode - a microphone preamplifier
(Take all safety precautions even when working with battery operated equipment such as the electron tube V6). (If monitoring with headphones always reduce dramatically the volume before changes and listen to ordinary to soft levels).
This technique reminds preemphasis demphasis as used on magnetic analog tape recording, FM radio preemphasis etc.
It may create nice HF peak limiting and the waveform then becoming rounded by the high cut filtering action. Similar to the high cut filtering action of the guitar amplifier speaker.
A similar preemphasis demphasis technique must be used on the Neumann U67, see Stephen Paul article.
References:
Flat frequency response from singer's vocal chords to listener's brain, Sound Picture Recording and Reproducing Characteristics - Loye, Morgan - JSMPSE
https://www.mixonline.com/recording/vintage-microphones-part-2-neumann-m49-m50-u67-and-u87-377061
800A Optimod Manual - Orban
www.261.gr - music not sinewaves
Interview of Mike Oldfiled on how he creates his guitar sound
Compensating for flat frequency response to listener's brain by removing the tube on omnidirectional microphones
At your own risk.
There is a thin tube usually used in omnidirectional microphones (see references) to extend their frequency response down at lower frequencies and then dropping abruptly.
But many otherwise great sounding microphones sound bass heavy to listener's brain on vocals due to Fletcher- Munson, voice effort curves etc when used for intimate close micking.
How would for example the fabulous Sennheiser MD21 sound with the tube disconnected? It is documented on Trashblitz that it is difficult to open and especially closing back the microphone.
References:
Elements on Acoustical Engineering - Harry F. Olson
Microphones - Robertson - BBC engineering training manual
Sennheiser MD21 - Trashblitz
Flat frequency response from singer's vocal chords to listener's brain, Sound Picture Recording and Reproducing Characteristics - Loye, Morgan - Journal of the Motion Pictures Sound Engineers
Some common elements of Neumann M50 and Grampian DP4
The Neumann M50 is possibly one the best microphones ever made.
It is mentioned in an interview of Al Schmitt.
The Grampian DP4 is also omnidirectional.
A desirable version of M50 has a metal diaphragm. So does DP4.
They both have a significant rise in frequency response above 2KHz.
Stephen Paul explains this is important as the high frequencies are absorbed by air. This should be significant when recording a large orchestra in a big room.
If a stepup transformer and electron tube head amplifier such as Pleiades V6 is connected to DP4 they have another thing in common. A very low noise, simple and great sounding front end amplifier. The Pleiades V6 is operated by batteries and the schematic as anything else Pleiadss is open source.
Why omnis? Although not as popular omnidirectional microphones are sounding great and for close vocals too. For example Karen Carpenter recording with a U87 stuck to omnidirectional pattern. Close to you.
The absorption of HF due to air molecules and the difference in diffuse sound field response compared to free field are 2 different phenomena.
References:
Neumann M50 frequency response
Grampian DP4 Technical Data
https://martinmitchellsmicrophones.files.wordpress.com/2016/09/grampian-dp4-page-3.jpg
Neumann M50 schematic
Pleiades V6 schematic
https://m.youtube.com/watch?v=4eFneKlvlLQ
https://www.mixonline.com/recording/vintage-microphones-part-2-neumann-m49-m50-u67-and-u87-377061
https://www.gearslutz.com/board/so-much-gear-so-little-time/518947-anyone-use-omni-mics-vocals.html
http://recordinghacks.com/microphones/Neumann/M-50
Microphones - Boré, Peus - Neumann
Monday, March 26, 2018
Ohm's law is an approximation, inductance can vary with frequency and relativity
Voltage equals electric current x resistance. V=IxR. Yes?
It depends. We assume that R is constant. But it is not always. It may depend on temperature, on the current range involved, the material etc. Filaments for example are notoriously non constant resistors.
Similarly with inductors. The reactance of an inductor is Ohms is proportional to inductance and frequency. But the inductance itself may depend on frequency. For example a mumetal wound core may exhibit a loss of inductance at roughly above low mid frequency band.
For example the Canford inline microphone transformer used on previous Pleiades experiments. By measuring the primary inductance with a digital LCR meter we measure 400mH at high frequencies. But when the meter is emitting a low frequency the measured inductance is much more. In fact the reading is 1.7 Henries.
This affects the sound a lot. For example the effective low cut (Pleiades filter) is less when a microphones is connected.
This also reminds relatively. The mass of a mass depends on speed.
Nature is nonlinear.
Bibliography:
Conceptual Physics - Hewitt
The Feynman Lectures on Physics - Feynmann, Leighton, Sands
Electronics, A Systems Approach - Neil Storey
Sunday, March 25, 2018
Pitch Perfect a Cappella Singing
https://m.youtube.com/watch?v=g-ByPeSVxyQ
From the film Pitch Perfect
1 mic 1 take at Capitol Studios
https://m.youtube.com/watch?list=PLVFiKflBZkYvpGoDFnC72b6RDvBgp2aSf&v=Bfj3ACD4DJU
A quick look at the music industry
By searching on Google with keywords Capitol Studios Wiki
It was found that the Universal Music Group (which now owns EMI too) is owned by Vivendi.
https://en.m.wikipedia.org/wiki/Capitol_Studios
By clicking on Vivendi it is interesting to read the story:
https://en.m.wikipedia.org/wiki/Vivendi
It is then interesting to click and read on Edgar Bronfman Jr:
https://en.m.wikipedia.org/wiki/Edgar_Bronfman_Jr.
It is of course very interesting to read:
https://en.m.wikipedia.org/wiki/Universal_Music_Group
The Capitol Studios Microphone List (Studio A)
https://www.capitolstudios.com/wp-content/uploads/2015/05/MicrophoneInventory.pdf
Reference:
https://www.capitolstudios.com/studios/#studio-a
Saturday, March 24, 2018
A great example of B flat major 7th
The B flat major 7th is one of the best sounding chords on our planet.
It can be found on a few songs:
The Great Gig in the Sky - Pink Floyd
Careless Wisper - George Michael
Supertwister - Camel
Etc
It consists of B flat bass, the 7th interval from bass (or base from the Hellenic βασις) which is 7 natural notes above the foundation B. Ie the note A. The 3rd interval is also taken and usually the 5th too. So it is Bb D F A.
Another fabulous example of B flat major 7th is
Safe in your Arms - Jimmy Simmerville
https://m.youtube.com/watch?v=aY-Efl0nIi4
At the chorus, Safe in Your Arms is sung by the note A. At Arms the bass becomes B flat and the amazing chord is made with the 7th prepared from the previous A notes (Safe A in A your A).
Reference:
Bach Bass Rules
http://normanschmidt.net/scores/bachjs-general_bass_rules.pdf
OMD
Electricity
https://m.youtube.com/watch?v=Y43XLVqjytQ
Enola Gay
https://m.youtube.com/watch?v=d5XJ2GiR6Bo
Interesting documentaries and interviews of OMD can be found on YouTube.
The quickest meal?
At your own risk.
Adapt it to your taste, health needs.
A Pleiades meal.
A Pleiades meal.
We place thin oat flakes in a bowl or on a plate.
We add whole sesame seeds.
We slowly add filtered water.
We stir.
We then add black raisins.
Small pieces of walnuts.
Pistachio nuts or whatever we feel we like.
We add whole tahini (whole sesame paste).
The water and tahini will blend creating a milk like texture.
We add some Ceylon Cinamom.
It is ready
Οποιος δεν κλέβει ιδέες δεν φοβαται να αποκαλύψει καμια πηγη
Πηγη:
Για παραδειγμα το απιστευτο βιβλίο ζαχαροπλαστικής
Best of Pierre Hermé
Another Pleiades snack
Με δικη σας ευθύνη
Χρειάζεται μαρμάρινο γουδι.
Βάζουμε οτι αισθανόμαστε οτι θελουμε στην ποσότητα που θελουμε.
Πχ.
Λίγα καρυδόψιχα.
Χτυπάμε.
Λίγα αποφλοιωμένης αμύγδαλα.
Χτυπάμε.
Λίγα φυστικια Αιγινης, κουκουνάρι κτλ.
Χτυπάμε.
Λιγο αποξηραμένη 2 ημερών τσουκνίδα.
Χτυπάμε καλα.
Φλούδες φρεσκοκομενου λεμονιού.
Χτυπάμε και αλεθουμε καλα αφήνοντας την εντροπία να κανει τη δουλειά της.
We spread the mixture on barley rusks for example.
Η το κανουμε πιτάκια σαν γλυκα τυροπιτάκια.
Βάζουμε και κανέλα Κευλανης.
Η ιδέα για τις λεμονοφλουδες στο γουδι ειναι του Alexandre.
Προσοχή με το γουδι. Κανουμε ενα διάλειμμα και αν αισθανθούμε πόνο η οτιδήποτε σταματάμε αμέσως.
Ένας τρόπος να καθαρίσουμε το γουδι ιςως ειναι να χτυπήσουμε λίγες σπασμένες νιφάδες βρώμης.
How similar is preparing a meal to playing music to electronics
You try something and you let your brain tell you how it is.
Then you try again...
Η καλύτερη αντιμετώπιση για τον κλέφτη ειναι να του πεις οτι ήταν δικό του, της
Πηγη:
Άθλιοι - Βίκτωρας Ουγκω
Pleiades V6 microphone booster amplifier solar powered
It is an electron tube low noise booster amplifier. Since the current consumption is typically only 150mA (the deliberately reduced heater current of EF183) and the voltage required is less than 4V, solar cell operation is possible.
For example a small solar panel can be on top of the octagon box.
A special arrangement can be made to charge the internal batteries even when there is no direct sunlight. But attention should be paid to protective circuits for not overcharging the batteries.
Reference:
Pleiades V6 schematic
A misconception of automatic cathode bias by a cathode resistor
Referring to the usual amplifier circuit with a cathode resistor connected between ground and electron tube cathode.
It is not that the Rk increases the potential of the cathode.
It is that the already positive potential of the cathode by the electrons left to the electron cloud is decreased at the other side of the resistor by voltage drop (ohms law).
This other side is connected to ground and the grid is connected there too.
The misconception may have arisen from the fact that tubes were usually operated at high anode potentials. We were always interested in further increasing the negative bias and this effect may had been overlooked. That the bias was already negative!
It is very easy to verify that the cathode is already positive or the grid negative by just connecting only the heater voltage to an electron vacuum tube. Any voltmeter even of low input impedance will show a significant of few hundred millivolts negative potential at the control grid with respect to the cathode.
It is this internaly produced negative bias that blocks operation of an electronic valve or electron tube at low anode voltage.
To circumvent this situation and make an electron tube operate at low battery anode voltage at least 2 ways are possible.
1. Connecting the secondary for example of the input transformer to grid. Then adjust exoerimentaly the bias by a variable cathode resistor. At very low values of Rk the tube will operate normally as the positive as explained above cathode will negate through Rk the negative bias of the grid. See Pleiades V-1 booster microphone preamplifier. More investigation is needed as there may thermionic current flowing in the grid circuit through the secondary winding. Another way of looking at this example is that the cathode resistor with its lower side being connected to grid acts as an electron accerating resistor as effectively we connect a positive potential (the cathode) to grid through a resistor. This is why when Rk becomes 0 the anode current becomes so excessive even using just 6 volts anode potential.
2. Another way to make an electronic valve operate at low Va is connecting the secondary of the input transformer for example, through a coupling capacitor to the control grid. As explained above the grid is already negative because the heater voltage is applied and there are electrons boiling off the cathode towards the grid forming the electron cloud or space charge. An anode to grid resistor of a few Megohms can be used to negate this negative bias and make the electron tube to operate at a very low anode potential, typically 4 volts on a triode connected EF183. Using the above technique the grid bias may still be negative but less so.
Note: Whenever we say grid bias we mean the voltage of the grid with respect to cathode.
Under heating the cathode has a beneficial effect on the above described techniques as the electron cloud is reduced.
References:
Operating Features of the Audion - E. H. Armstrong
Pleiades V-1 - euroelectron
Pleiades V6 schematic - euroelectron
On preserving electron tube transconducatnce at anode potential as low as 3V - euroelectron
Friday, March 23, 2018
How to have a world class sound quality with the MD441 U3 and Sony TC-D5 pro
On the next euroelectron post.
Sennheiser MD441 U3 and Pleiades V6
At the moment they do not mate well.
(See later post on how the problem was accidentally solved):
http://euroelectron.blogspot.com/2018/06/the-sennheiser-md441-u3-to-pleiades-rl.html
The Pleiades V6 with the 1:10, 140mH and 10:1 800mH input, output transformers make this world class mic sound a bit honky tong. There is an almost nasty exaggeration on mid range.
Signal path, setput:
Male singing voice at 4in to 8in - MD441 U3 - Pleiades V6 - Sony TC-D5 Pro - HD580
Next the MD441 U3 was directly connected to Sony.
The sound was almost unusable because of extreme proximity effect. Perhaps a quite large distance the sound could natural but the acoustics of the living room do not allow this. The gain on the Sony had to be increased but it was mostly that bass content was heard due to the proximity effect.
Next the MD441 U3 was connected to the small ratio BBC transformer and then the Sony TC-D5 Pro.
The sound was amazing. One of the smoothest sounds heard on the Pleiades experiments. There was nice proximity compensation. Mid and treble was as sweet and smooth.
There was some increase in impedance and voltage which suited very well the MD441 U3 and the Sony TC-D5.
There was some electromagnetic hum pickup up noise as the BBC transformers were just in an aluminum box and it is not certain that they were made for low level microphone work. Their inductance and sound made the MD441 sound like the diamond it is.
Signal Path, setup:
Male singing voice at typically 5in - BBC LL/210A transformer 115mH:382mH - Sony TC-D5 Pro - HD580
The gain on the Sony had to be set to fairly high and fortunately there is a 1:1.8 stepup from the transformer. But the sound was amazing.
More experiments are needed including winding a 1:1.8 transformer which stated inductances on a supermalloy ring core by Magmet or Arnold or a mumetal tape wound core or a Nanoperm nanocrystalinne tape wound core by Magnetec.
It is certainly good news that a world class sound can be obtained by just adding a signal transformer with the fabulous MD441 U3 and Sony TC-D5 Pro.
If the signal to noise ratio proves to be high without the V6 booster preamp an even more portable signal path is possible. Boosting and proximity compensation is made by just a transformer between mic and preamp. And a signal transformer is a passive device, therefore no extra battery (or power consumption) is needed.
(Later addition): see also AKG D1000 and Pleiades V6 post. Is the cause of lesser sound the input transformer of V6 being overloaded by the big bass due to the proximity effect?
Schaub Lorentz SM200 and Pleiades V6
They mate very well together. But there is a lot of proximity compensation since the mic is 750Ω and the input transformer currently used on the Pleiades V6 has a primary inductance of 140mH. So one has to sing at about 2in to 3in from the mic. This is good for a high signal to noise ratio.
In order to try it at a larger distance the input transformer was unplugged. And the internal transformer of the mic which transforms to an output impedance of 50KΩ was connected to the grid of the EF183 through the 22nF coupling capacitor.
There was phase reversal so the phase reversing adaptor on the Sony was removed. The sound was excellent.
Signal path, setup:
Male singing voice at 6in to 8in - Schlub Lorentz SM200 from it's Hi Z output - Pleiades V6 without input transformer - Sony TC-D5 Pro - Sennheiser HD580
Great body of sound, extended and detailed treble, nice midrange. There is something very nice about this mic and its transient response.
It is sensitive to handling and electromagnetic noise. The former should be because it is a directional moving coil so the diaphragm resonant frequency is placed low. One of the reasons for the latter may be the internal transformer.
Reference:
Pleiadss V6 schematic
The making of Pleiades V6 microphone amplifier
It would be nice if such a book existed with top quality photos such as the Pierre Hermé book on pâtisserie.
Another 2 great books by the BBC
Engineering Division Training Manual - The British Broadcasting Corporation - 1942 - Iliffee
Studio Engineering for Sound Broadcasting - Members of BBC Engineering Division, editor Godfrey - Iliffee
Connecting 2 microphones in parallel, BBC way
Each mic with a series variable resistor. The 2 resultant circuits connected in parallel to a repeating or signal transformer primary winding.
Reference:
Engineering Division Training Manual - The British Broadcasting Corporation - 1942 - page 76
Thursday, March 22, 2018
Another interesting mic
Should be the Beyer M61 moving coil.
There is some information on Trashblitz.
Wednesday, March 21, 2018
The Grampian DP4/L still sends for tea the rest mics
More world class moving coil mics where tested and the DP4/L sends them to the cleaners. Well,the above comments may be exaggerations but in all those subjective brain perception tests this is how it is felt.
At the moment it is the Pleiades reference mic.
Grampian say in the mic operating instructions that it is the mic against which all others are judged. This is a very bold statement. They knew.
Perhaps the Pleiades 1:10, 140mH input transformer used in the Pleiades V6 booster and the DP4/L match like hand and glove...
But still it is the best sound of all the previous experiments with the mics and different tranformere mentioned.
Signal path, Setup:
Singer's brain - Male voice singing A Taste of Honey - mic at 1in to 6in - Pleiades V6 - Sony TC-D5 Pro - Sennheiser HD580 - Listener's brain
On voice not loud, not too soft...
Compared to the DP4/L...
The Schaub Lorentz MD200 sounds too bright but great (understandable since it is of 750Ω impedance)
The Electro-Voice RE-15 sounds amazing and great but there is something even more natural on the DP4/L
The Electro-Voice RE-16 same as the RE-15 but more bright and you can go closer than the RE-15 for same bass.
The Electro-Voice 635a amazing but still the DP4/L more natural on detail and less bright. As if the DP4/L does not have the rising HF response. Could it be that the DP4 has compensation for the presure doubling effect, ie is flat at 0 degrees incidence therefore deliberately non flat for random field?
The Sennheiser MD21 HN amazing and natural and perhaps smoothest but perhaps bright.
The MD211 great and full but with less natural and less bass. (The MD211 should be connected to a transformer primary winding input inductance of typically 300mH. Also a proper cable needs to be made for it. The SM200 and MD211 were connected with untwisted alligator cable clips to the connector after the mic). It was also bright and of course possible RF pickup did not help.
The Shure Unidyne III, vintage SM57 great but still the DP4 more full and natural and easy while being lively too. Is there something important in metal diaphragms?, is the DP4 diaphragm made of aluminum?
A mic that sounded great to the above setup is the Sennheiser MD112 although not directly compared to the DP4/L yet.
The DP4/L has an amazingly low handling noise. Low hiss. No buzz. The most likely reason is that there is no transformer inside. So one has direct access to the amazing 25Ω voicecoil.
Compared to the other mics the DP4 needed more gain increase on the Sony since it is 25Ω but who cares. The gain adjusting potentiometer on the Sony has to be at 4 instead of 3 out of 10 for example. Connected as all the other mics to the Pleiadws V6 booster it was possibly the mic with the best signal to noise ratio.
Η Κανελινα, οι σοφοί Γλάροι και η Αφοβία
Σ' αυτο το επισοδειο η Αφοβια εμφανίζεται και τους λέει οτι αυτη υπάρχει ενώ ο φόβος δεν υπάρχει.
Η Κανελινα πετάγεται απο την χαρά της και όλοι μαζι χορεύουν και τραγουδούν στην μαγική παραλια κατω απο τις σοφές ακτίνες του Ηλιου που δεν αφηνει καμια σκια στην αλήθεια.
When you are the first to bring something to the light...
it looks like you are the first who have thought it.
Πως να κατασκευάσετε πιθανότατα το καλυτερο booster μικροφώνου στον πλανήτη
Στο διπλανό euroelectron post.
How to make possibly the best booster microphone amplifier in the world
On the next euroelectron post.
Pleiades V6, the child of RCA BA-2C and Neumann U47
Canelina the cat and her friend the patient tortoise who for obvious reasons winds the ring core transformers are very proud for the Pleiades V6 microphone booster or front end pre amplifier.
By looking at the schematics the V6 can be seen to be derived from the world class RCA BA-2C and Neumann U47 front end amplifiers, hopefully inheriting the best gene code from its mum U47 and dad BA-2C.
An evolution difference is that the little kid V6 is operating by just one 4V battery powering both heaters and anode. So you can take the kid to the beach, forest etc.
The Pleiades V6 is open source. For anyone who wishes to build, experiment, improve. Please take all safety and health precautions when experimenting with electronic circuits.
Describing the V6 in reference to U47 and BA-2C.
The ribbon, moving coil microphone, condenser microphone is connected to the primary of the input transformer as on BA-2C. The V6 input transformer is wound on the Magnetec Nanoperm 070 ring core. The number of primary turns dictates the primary inductance which in turn can be used to compensate for bass heaviness or not of the mics used.
The stepped up voltage which is of higher impedance will drive the grid through a capacitor as the condenser capsule on Neumann U47. The capacitor is used so that the grid is free to assume the DC voltage it wants. At very high input signal voltages the rectification cathode, grid diode effect will make the grid more negative. So there may be a voltage gain change as on a compressor as on U47 for very large signals.
All the family, BA-2C, U47, V6 have the electron tubes triode connected. Anode or plate, suppressor grid and screen grid connected together.
The U47 uses lower voltage on the anode than the BA-2C. The V6 much less.
The U47 has a lower cathode resistor than the BA-2C with Neumann's trick of passing the heater current through it to create a given voltage drop. The Pleiades V6 has an even lower cathode resistor. In fact it is almost 0. So no bypass electrolytic capacitor again is needed.
The cathode resistor is reduced to 0 so that the negative bias is decreased. This makes low anode voltage operation possible. But there is another trick on the V6 to make even less anode voltage operation possible. The electron tube internal bias is still negative (very easy to verify by an external voltmeter). This is because the heated cathode has lost boiling electrons to the cloud and the remaining lonely protons in the cathode atoms are positive. So the cathode is more positive wrt grid or the grid more negative wrt cathode. An external biasing resistor of typically 8MΩ from anode to grid further decreases the negative bias. The electrons are now free to travel to the anode by only 4V anode potential. The current can be much more than 100-200μA and we have a normal transconducatnce and low anode resistance since Va is low and Ia relatively large. Gain is dictated by the geometry of the electron tube.
On U47 the heaters of the VF14 are deliberately underheated for low noise, low temperature in all electrodes therefore low secondary electron emission or even photo emission effects. And most importantly of all, for better sound. On the V6 the heater voltage is even more reduced to less than 3V (compared to 6.3V). This is possible by the very low anode voltage operation. And who needs more billions billions of electrons than are needed to carry the music from cathode to anode? The very low heater voltage apart from the above mentioned advantages keeps power consumption very low. To a typical 150mA making battery operation a true joy.
The signal from the anode does not pass trough an anode resistor. But for less thermal noise and higher anode voltage through the output transformer secondary. Just like BA-2C.
The output transformer is again wound on a Magnetec 070 nanocrystalinne tape wound core. For the number of turns used or inductances please refer to a previous euroelectron post. The output is from the secondary winding, again balanced, low Z, typically 300Ω ready to feed generously with low noise and big natural sound a low Z microphone preamolifier. Just as one would connect a U47.
So there it is. V6, the child of U47 and BA-2C. Made with 2 signal transformers, 1 EF183 electron tube, 1 resistor, 1 22nF capacitor, 1 battery. A pure and simple class A operation (electrons flowing all the time) amplifier circuit.
The battery gives complete absence of all other sorts of AC hum electromagnetic noise.
The 4V is always connected to the anode and a switch just supplies the heaters providing the most quiet and smooth turn off or on.
Everything can be built and fit inside an octagon orange box.
So far favorable operating conditions are. Vb=3.9V. Rag=8MΩ. Cc=22nF. Heater voltage such that Ia is typically 50μA. Greater or higher Vh gives a whole range of sound palettes and the prototype may have a 10Ω variable wirewound resistor in series with the heater circuit. The transformers used on the Pleiades breadboard jig developing stage are 1:10 with 140mH primary for the input transformer and 10:1 with 800mH secondary inductance for the output transformer.
The output impedance at pins 2,3 is typically 300Ω. The grid from the way it is biased presents an impedance of aproximately 100kΩ. The amplifier is so low noise that the equivalent input noise resistance looking at the grid should typically be 2.5KΩ. So referring to input pins 2,3 the equivalent noise resistance is only 25Ω which is great even for 25Ω microphones. The input impedance at pins 2,3 is 100KΩ:10:10 or 1KΩ. Transformers of smaller turn ratio can be used too. More stages can be added and an interstage low crossection core interstage transformer can be used for analog simulation of analog magnetic tape recording with saturation on peaks or instantaneous peak limiting. Recording, playback preemphasis, deemphasis (with the interstage transformer in effect being 2 magnetic heads kissing each other in the air gap) is therefore possible, this may be the other child, possibly called Pleiades V7.
References:
Neumann U47 schamatic
RCA BA-2C schematic
Pleiades V6 schematic
On Preserving Transconductance of Electron Tubes at Anode Potential as Low as 3 Volts - euroelectron
Operating Features of the Audion - E.H. Armstrong
Tuesday, March 20, 2018
The Cinderella Microphone
The last foot your try is the best one.
After spending countless hours on eBay microphone hunting...
Well it is not always hunting, usually the best ones are the ones that nobody wants...
After a few years on eBay searching and listening to perhaps the best moving coil microphones on the planet...
And now that the Pleiades V6 front end amp is up and running so that any mic is like being connected to an electron microscope...
The best omni so far is the Grampian DP4/L.
In fact the best mic so far. So big, clear, punchy, natural, HF detailed, big bass but no bass heaviness, smooth but live midrange, low noise...
And so far from the constant D directionals is believe it or not the Schaub Lorenz SM200 with squarish cross section, made by Beyer?. Natural, nothing disturbing. excellent HF detail, smooth and live midrange, nice bass, not bass heavy, you can sing close to it, there is a bit of hiss.
From directionals so far the miraculous RE-15 should be top. A direct comparison between the 2 has not been made yet.
Special thanks to:
Martin Mitchel
For his rediscovery of the Grampian DP4/L
Trashblitz
For his mentioning of the name Schaub Lorentz on the M55? post.
Of course pay attention to the setup. For example the mics are terminated by 140mH input transformer primary inductance. And a world class BA-2C or Neumann U47 based booster amp is used, electron vacuum tube, 4V battery powered, the Pleiades V6. The schematic as everything Pleiades is open source.
140mH is low for some 200Ω omni mics (due to bass cut) but most of the top class mics had been connected to a higher primary inductance transformers, eg. 200mH, 300mH, 400mH. See other euroelectron posts.
Signal path, setup:
Male voice singing A Taste of Honey (in C minor) at 2in to 6in - microphone - Pleiades V6 head amplifier with (1:10, 140mH input transformer primary) - Sony TC-D5 Pro at balanced mic in, in mono mode - Sennheiser HD580 precision
It will not be mentioned to which mics they were today compared to. Let's not give them any more hard time.
References:
Pleiades V6 schematic - euroelectron
Neumann U47 schematic
RCA BA-2C schematic
http://www.coutant.org/ba2c/index.html
Monday, March 19, 2018
This first upload of example of Bach Bass Rules on YouTube
Piano playing by ear brain.
On renewablemusic YouTube channel.
The song used: A Taste of Honey
https://m.youtube.com/watch?v=0tEx-_akNWk
Reference:
Bach Bass Rules PDF
http://normanschmidt.net/scores/bachjs-general_bass_rules.pdf
Interesting information on legend producer Joe Meek
By searching:
Recodding Iconoclast Joe Meek Heard a New World - Electroninc Musician
And the books:
The great British recording studios.
Joe Meek's Bold Techniques.
Why do the Joe Meeks, Phil Spectors, Edwin Armstrongs of this world get into trouble?
Michael Jackson in the list too and so many others.
By reading the wikipedia article on Joe Meek it can be seen that there was fear in his heart.
But fear does not exist.
He won the case on royalties 3 weeks after his death.
Armostrong won his patents after his death too.
Only if they could wait for a while.
Why do these things happen.
An interesting explanation can be found on Fringe Knowledge for Beginners - Montalk.
Un-Phobia is perhaps the most important of all. Fear does not even exist.
And it is also how one can handle money and success.
Vangelis said in his Quatar interview (YouTube) that success... "Why should one be successful?"
Joe Meek's place was found full of un released material.
Of course they must have been released after his death.
How difficult must it be someone giving all his energy, money, being successful and then become depressed when he, she is not.
When the key is in the Epictetous Enchiridion book.
"It has nothing got to do with you."
And in a Snoopy Cartoon on the book Musical Acoustics - Doland Hall, the girl asks the boy playing the piano.
"What if after all this practice you do not become rich and famous?"
And the boy replies while playing...
"The joy's in the playing"
Should then an inventor, producer etc give everything for free without ever signing anything?
For example a producer handing the master tapes or files to the artist without asking for anything back. Tax is out then too.
An inventor just publishing everything and not asking for a patents.
Οταν δεν οικειοποιούμαστε τίποτα, έχουμε πρόσβαση στα παντα.
The most important is to be free.
How about a list of mics a famous producer did not use
For example it should be found on google by searching Joe Meek and Grampian GR1 ribbon microphone etc that Joe Meek may had not used these fabulous mics although he had them.
But he may had used them, you never know.
Sunday, March 18, 2018
The great books of Harry F. Olson
Anyone wishing to go deeper into how microphones are designed should search for the excellent books of Harry F. Olson.
Electrical analogies of acoustical and mechanical systems throughout. So that patent reading on the classic microphones can be better understood.
His classic Elements of Acoustical Engineering was the basis of the BBC Engineering Training Series, Microphones book as it is stated in its first pages.
Other examples of amazing books by Olson:
Dynamical Analogies.
Music, Physics and Enginerring,
Acoustical Engineering which must be the 3rd edition of the previously mentioned book.
And many more.
It is also interesting to see the parent list of Olson on Wikipedia. For example there is one on improving the sensitivity of ribbon microphones.
The best RCA ribbon and lowest noise mic ever made?
It is described and tested by Olson on a classic JASA Olson paper.
Olson went as far as putting it inside a vacuum chamber so that the electromotive force (noise) produced by the motion of the diaphragm (ribbon) due to the thermal agitation of molecules imprinting upon the diaphragm (ribbon) could be measured.
It is very interesting that an electron tube head amplifier was prefered to be used instead of a FET because of its lower noise and absence of thermal noise.
Reference:
Microphone Thermal Agitation Noise - Harry F. Olson - Journal of the Acoustical Society of America
An amazing booster microphone preamplifier by RCA and Pleiades amplifiers
The RCA type BA-2C microphone booster or pre preamplifier or head amplifier.
So many years ahead of its time.
It is a front end microphone preamplifier so that a ribbon or moving coil microphone can be connected. And it gives fair play to all the low noise and sensitive ribbon and moving coil microphones.
Fair play by giving them a low noise head amp like condenser capsules have inside the microphone itself.
Many details of the RCA microphone booster can be found on the excellent courant website.
http://www.coutant.org/ba2c/index.html
The Pleiades V5, V6 head amplifiers can be thought of as a more modern implementation of such type of amplifiers as they operate with battery and just 4V to 8V typically, including anodes.
It is known that battery operation reduces many aspects of noise in preamps.
On the Pleiades very low noise operation is further helped by the very low anode and heater voltage. Minimising secondary electron emission effects etc.
Operation at such low voltage is possible by the anode to grid few Megohms biasing resistor.
A 2 stage stage with potentiometer in between can be derived.
Or perhaps a 3 stage with a saturating inter stage transformer for instanteniously peak limiting. Thereby simulating analog magnetic tape recording. See other euroelectron posts.
A three stage head or front end amp could be arranged as follows.
The mic drives through the input transformer the first tube.
A big interstage transformer feeds the second electron tube.
A small interstage transformer driving the 3rd electron tube provides recording preemphasis or peak saturation limiting.
The 3rd tube with high cut implemented (mathematical integration), like a reel to reel tape playback amplifier.
An output transformer creates low output impedance and the adjustable low level but loud sounding output of the booster preamp can then feed an ordinary mic preamp.
This may be called the Pleiades V7.
Pleiades concepts and schematics are open source.
References:
RCA BA2C on www.coutant.org
http://www.coutant.org/ba2c/index.html
Pleiadws V5 or V6 schematic
Neumann U47 schematic
Saturday, March 17, 2018
The lower Va (anode voltage) the lower Vh (heater voltage)?
Quite possibly so.
It can be seen on all electron tube textbooks, cathode temperature vs anode voltage curves, for example for diodes.
Would it be possible to operate an EF98 or EF97 with just 1.5 volts for both the heater and anode circuit? On a Pleiades V6 configuration?
Or is the EF183 triode connected the best electron tube on the planet?
Reference:
Pleiades V6 schematic
Testing a microphone is a great psycho acoustic experiment
It may for example involve how it performs in an environment from singer's vocal chords to listener's brain.
And therefore this test does not involve only a mic. It may be a mic, an input transformer, a head amp or prepreamp,..,and how all these interact.
The monitoring system quality is extremely important.
On the Pleiades experiments the Sennheiser HD580 precision headphones are used.
Reference:
Flat frequency response from actor's. singer's vocal chords to listener's brain, Sound picture recording and reproducing characteristics - Loye, Morgan
Collecting microphones is very addictive
Is it a bit like trying many sex partners until the perfect one is found? And one seems never to be satisfied and the search goes on..
And some microphone shapes can be a phalic symbol. Why should men collect mics? They already have one!
Microphones are great converters of molecule vibration to electron vibration.
But we must not forget that all we humans need is love.
It is so often that what we were trying to find had already been there.
Reference:
We are trying for something that has already found us
Jim Morrison
AKG D112 to Pleiades V6 to Sony TC-D5 Pro
Very nice combination.
The D112 microphone has a frequency response curve very similar to Neumann U47.
The V6 is similar to the Neumann U47 head amplifier.
An amazing sound. Full bass but not heavy, great mid, fantastic treble detail.
Signal path, setup:
Male singing voice at 7in - D112 - V6 - TC-D5 Pro - Sennheiser HD580
The inout transformer used inside the Pleiades V6 has an input inductance of 140mH to compensate for proximity effect, and a turns ratio of 10.
References:
Frequency response curves of U47, D112
Pleiades V6 schematic
Neumann U47 schematic
Thursday, March 15, 2018
The BBC have always had great faith on ribbon and moving coil presure microphones
After more than 70 years...
References:
High quality sound production and reproduction - Hadden - BBC
BBC Engineering Training Manual, Microphones
The best book on acoustical engineering?
Elements of Acoustical Engineering - Olson
Harry Olson, the man behind the development of ribbon microphones.
https://pearl-hifi.com/06_Lit_Archive/14_Books_Tech_Papers/Olson_Harry/Acoustical_Engineering.pdf
Attention before dismissing a microphone part 2
It seems singing needs less bandwidth than speech. When we sing more bass and treble frequencies are produced. And contrary to intuition the high male notes may have may have more chest low content.
And a microphone that does not sound too good on speech for exactly the reason it may be perfect for singing.
For example:
Are you Lonesome Tonight - Elvis Presley
It may be safe to assume that no EQ change was done between the speech and singing part, see reference.
And of course a mic for singing should be tested by singing, not speaking, common sense.
Reference:
Interview with Elvis Presley's Sound Engineer, Bill Porter by Michael Fermer
https://www.elvis.com.au/presley/interview-with-elvis-presleys-sound-engineer-bill-porter.shtml
Wednesday, March 14, 2018
A great book on microphones by the BBC
BBC engineering training manual, Microphones.
It explains so much. For example it is a joy to read what mass control. resistance control, stiffness control on microphone membranes mean, and what happens on each type of microphones.
https://www.bbceng.info/additions/2016/BBC%20Engineering%20Training%20Manual%20-%20Microphones%20(WW).pdf
A great book on learning electronics by the BBC
Engineering division training manual 1942 - BBC
It explains how inductors operate, transformers, electrons in audio, antennas etc.
http://www.americanradiohistory.com/Archive-BBC-Books/BBC-1942-Engineering-Training-Manual.pdf
A variable input inductance microphone preamplifier input transformer
A way may be using a ring core in a variable or autotransformer arrangement
So as the moving slider(s) selects less turns the input inductance is reduced and the turns ratio is increased.
So proximity compensation is increased. As bass drops the overall gain is compensated by the increased turn ratio and the fact that the singer is closer to the microphone.
Multitap input transformer for the Pleiades V6
For example there can be 4 inputs on the Pleiades V6 but only one input transformer used.
As an example let as suppose that the octagon aluminum die cast box has on some of the sides 3 female XLR female sockets and one 1/4in input socket.
The core has 3 primary windings and each winding is connected to each balanced input.
One of the balanced inputs can be of 140mH by being connected to the 140mH input transformer winding. In fact the wire coming out of the core can be twisted and directly connected to pins live, return ie 2,3. This is useful for connecting 25Ω mics such as Grampian DP4/L or STC 4021 apple and biscuit etc. Also for connecting a Sennheiser 200Ω MD21. Or for directional microphones of about 200ohms such as AKG D112, D1000, Shure SM57 or Unidyne III, Sennheiser MD441, Electro-Voice RE15 etc when these are used for singing at a distance of a few only inch thereby compensating for the proximity and other psychoacoustic effects. See next euroelectron post on the importance of input inductance rather than impedance. Such a transformer has been tested on the V6 and these mics expect the 4021 with very good results. It is wound on the Magnetec 070 ring Nanoperm core, has a ratio of 1:10 and input inductance of 140mH. See other euroelectron posts.
The second input can be of more primary turns having for example an input inductance of 300mH. This winding would having more turns and since the secondary on this example is constant the turn ratio would be less. This winding would give a more bass extension making it suitable for example for... A Sennheiser MD211N for vocal singing. An MD21 for recording drums. 200Ω directional moving coil microphones for vocal singing at 1-2feet for example. It is important to understand that more turns gives a higher input inductance. So the impedance at low frequencies is not reduced. Therefore there is no voltage drop at the mic's terminals at low frequencies. Other possible uses are: Distant mic capture with a Gramoian GR1/L or GR2/L 25 Ω ribbon microphones for full range sound capture to listener's brain. The fact that the turn ratio of this transformer may be less than 1:7 or even less than 1:5 should not matter at all for noise considerations as the equivalent input noise resistance of the Pleiades V6 is of the order of only 2500Ω. In addition microphone loading is minimal. For example with a turn ratio of 1:5 the input impedance of the grid which is 100KΩ is transformed to 100KΩ:5:5 or 5KΩ. So a mic of 200Ω sees a 5KΩ input at the frequencies of interest. An Electro-Voice 635a can be connected for more bass than the previous terminal.
Another winding of very few turns may be connected to the 3rd XLR input. The very low inductance can be of 14mH for example. This roughly means 1000 less than the secondary which is 16H. So a turn ratio of aboit 1:33. This may be used with a low impedance ribbon microphone such as the 25Ω Grampian GR1/L or GR2//L for very close singing voice of correct frequency response to listener's brain. A full spectrum sound with great high end detail. The best value of input inductance is best decided by the application of interest and the desired result.
The other input is an unbalanced one connected to the 22nF input grid capacitor. A switch may allow the secondary to be connected in parallel. The switchable low cut may be useful for example for compensating for exagerated bass frequency perception to listener's brain when an electric bass is directly injected to the control grid circuit.
Reference:
Pleiades V6 Schematic
Specifying head microphone amplifier inputs in terms of inductance rather than impedance
Input inductance is very relevant to sound.
For example it can compensate or not for the proximity effect, Fletcher Manson brain perception curves, Voice effort curves of human voice and singing production.
How impedance varies with frequency is important.
Perhaps the best is having both specifications. Or even more. For example what is the input impedance, what is the input inductance, how does impedance vary with frequency, what is the equivalent input noise resistance etc.
As an example of the above elements. One pre preamplifier can have 3 200ohm rated inputs. One with 1 Henry input inductance for orchestral applications, one with 300mH input inductance for voice or singing. And one with 140mH for close mic singng, compensating the proximity effect etc.
Input inductance depends on the number of turns of a coil in parallel with the input signal. It may be a Pleiades filter or the primary inductance of the input transformer etc.
These considerations may be important as what matters is not flat frequency response from mic to loudspeaker. But flat frequency response from producer's brain to listener's brain.
Reference:
Flat frequency response from actor's, singer's brain to listener's brain, Sound picture recording and reproducing characteristics - Loye, Morgan - Journal of the Motion Picture Sound Engineers
Coil Design and Cinstruction Manual - B.B. Babani
Tuesday, March 13, 2018
Hello to Bulgaria, Spain, Netherlands euroelectron viewers
And to all viewers from almost anywhere in the world.
Thank you all!
Attention before dismissing microphones
It may be that what is dismissed is the preamplifier interface connection.
The dismissed mic may be a diamond.
For example:
A Grampian DP4/L may be connected to a top class Sony TC-D5 Pro transformer balanced input preamp.
Due to the very low voltage output of the 25Ω voice coil of the mic the gain at Sony may have to be turned at max. Then there is hiss. But this is not the hiss of the mic.
The sound may sound just OK but nothing really special since we cannot judge something that is almost buried in hiss. It is like finding a diamond covered with whatever making it look like something covered with mud that has to thrown away.
When a top quality low noise head amplifier is connected between the two... as we should do with a condenser capsule, for example Neumann U47...
The sound becomes a few hundred times as big. With no hiss. The Sony input level potentiometer control would need to be just at 3 out of 10 with a soft singing voice.
The sound is bass full, without bass heaviness, with excellent mid and treble detail.
If the 25ohms mic is stepped up by a transformer to say 600ohm and then feeding directly the Sony TC-D5 Pro, although it would sound louder that at 25Ω there may not be the same top class of high frequency responce due to the loading to the mic. Assuming the TC-D5 pro has an input impedance of 4Kohms, the 600ohms are loaded by 4kohms.
Whereas if a battery operated electron tube headamp is used such as the Pleiades V6 the loading is much less. Assuming a 1:10 input transformer is inside the Pleiades V6 the 25ohm voice coil is stepped up to 2.5Kohms. But the input impedance looking at the electron tube grid is 100Kohms so the loading is minimal. Also the Pleiades V6 has a very low equivalent input noise resistance meaning it is a very low noise head amp. So the turns ratio can be 1:10 even with a 25ohm microphone. A typical value of the equivalent input noise resistance may be around 2.5Kohm. Calculating from righ to left, the input transformer makes it 2500:10:10 or 25Ω, very comparable to the mic. Also the mic is loaded by 100KΩ:10:10 or only 1KΩ.
The input inductance of this particular 1:10 input transformer is only 140mH. This is a joy to wind as the Magnetec 070 ring core is wound by only 35 turns of wirewrap wire for the primaryOr input winding. This is possible as the mic is 25ohms. 25ohm and 140mH give a turnover at around 28Hz. (This is found by 25Ω:2:3.14:0.140Henries. The same low input inductance can be used for connecting to directional 200Ω mics for compensating the proximity effect. For example the AKG D1000, AKG D112, Shure Unidune III or SM57. The Sennheiser MD441 for close vocals as well as the omni MD21 can be connected. The output transformer used introduces a -3dB point at around 100Hz. It makes a very balanced flat frequency response from singer's vocal chords to listener's brain. Otherwise the sound might have been bass heavy. But it all depends on the conditions.
Signal path, setup:
Grampian DP4/L - Pleiades V6 - Sony TC-D5 Pro - Sennheiser HD580
References:
Pleiades V6 Schematic
Neumann U47 Schematic
Flat frequency response from singer's vocal chords to listener's brain, Sound Picture Recording and Reproducing Characteristics - Loye, Morgan - Jkurnal of Motion Pictures Sound Engineers
The myth that dynamic or voice coil microphones do not need a head amplifier
Of course they do.
And then they send for tea most of the condensers, even the very expensive vintage ones.
The sounds jumps out, there is no hiss, all ambience detail from tens of meters away if gain is up. With a good moving coil microphone the sound is as smooth and big as it may get. Ribbon microphones too.
An example setup is:
Moving coil mic - Pleiades V6 prepreamp - a mic preamplifier
Similarly for ribbon microphones.
Other example is using just a JFET instead of an electron tube, see Pleiades K117 schematic. An output transformer would usually need to be connected too. But it works even without, just capacitor coupling. For example:
Moving coil or ribbon mic - Pleiades K117 - Telefunken V72
From the moving coil microphones the category of pressure ones have diaphragm that is acoustic resistance controlled broadband tuned near midland as directional condenser capsules should do.
So they do not have the harshness of omni condensers tuned at HF. They have the detail of condensers, but smoothness of high frequencies as the amplitude of the diaphragm must decrease with rising frequency for flat frequency response output. This is because the voltage output of moving coil mics is proportional to the velocity of the diaphragm due to the magnetic induction law.
And of course on moving coil or ribbon microphones the head amplifier can be meters away instead of having to be mounted right next the capsule.
References, bibliography:
Pleiades V6 schematic
BBC Engineering Training Manual: Microphones
http://www.bbceng.info/additions/2016/BBC%20Engineering%20Training%20Manual%20-%20Microphones%20(WW).pdf
Microphones - Borwick
Microphones - Boré, Peus - Neumann - PDF
Monday, March 12, 2018
How Steve Booker produced Stepping Stone - Duffy
Extracts from a hitquarters interview?
"I think you hear great music that has come from people who have just kept their heads down and just work incredibly hard. And within Logic you can develop a sound where you don't need to do anything else."
"I did Duffy's record on my laptop. It was only after I got paid for her record I could afford to buy a proper computer really".
Reference:
http://aimeeduffy.blogspot.gr/2010/03/interview-with-steve-booker.html
Unfortunately the link does not operate anymore
http://www.hitquarters.com/cgi-sys/suspendedpage.cgi?page=intrview/opar/intrview_Steve_Booker_Interview.html
Sunday, March 11, 2018
Why do Pleiades filters act as electromagnetic pop filters too
This is explained in some detail in the next post on Grampian GR1/L.
Why does the Grampian GR1/L ribbon mic needs so low terminating inductance to sound correct at small distance?
The inductance needed in parallel with this brilliant mic is ridiculously low, typically 3mH to 14mH.
The mic sounds correct without any EQ needed when recording at large distances, eg greater than 1-2 meters.
When we sing close to them the sounds gets extremely bass heavy and we need to compensate for the proximity and some psychoacoustic effects.
The fact that a so small inductance is needed makes input transformer design and construction a paradise. Especially if a Magnetec Nanoperm ring core is used the turns are so low the primary winding may consist of just say 7 turns.
Why such a low inductance needs to be connected in parallel?
It is best to find the right inductance exoerimentaly by what sounds correct to listener's brain. Increasing or subtracting turns until the sweet spot is reached for the particular voice, distance, song etc.
Here are some reasons of the very low inductance needed.
They are 25ohms so they need an inductance of 10 times less compared to a 250ohm mic for the same effect.
They are ribbon. So the bass increases the more we come close. At a few inches even the mid range would have increased.
The more softly or intimately we sing close to a mic the more bass or treble is produced by our vocal apparatus. This is described by the voice effort curves.
The more loud the acoustic reproduction is, the more our brain becomes sensitive to bass and treble. This is described by the Fletcher, Munson or equal loudness curves.
A proposed signal path for excellent signal to noise ratio:
Grampian GR1/L - Pleiades V6 head amplifier with a low inductance input transformer - a mic preamplifier
Since at very low frequencies the impedance of an inductor is very low, mich current is flowing through the ribbon. So there is a magnetic force to it as on ribbon loudspeakers. This force opposes it's cause which is our voice. If it did not oppose we would have energy from nothing which is against the law of conservation of energy. This is called Lenz's law. So the ribbon is damped and the pops are greatly reduced. Nevertheless you act at your own risk and always protect those precious excellent sounding mics.
References:
Microphones - Borwick
Flat frequency response form singer's vocal chords to listener's brain, Sound picture recording and reproducing characteristics - Loye, Morgan - Journal of the motion pictures sound engineers
Pleiades V6 schematic
Conceptual Physics - Hewitt
The Feynman Lectures on Physics - Feynman, Leighton, Sands
How to make a ribbon mic sound more detailed and bright than a condenser
There is no reason why they should sound only dark.
There is no reason why they shouldn't be at least as detailed as the best condensers or moving coils. Their diaphragm, the few micron thin aluminum ribbon itself is of extremely small mass. From Newton's law. Acceleration = force : mass . The lower the mass for given force the greater the acceleration.
They are tuned to a very low frequency.
So as the frequency is increased above this resonant frequency displacement drops as in all resonant curves. They are mass controlled.
But the velocity of the ribbon remains the same because the frequency is higher.
And since the emf or voltage out is proportional to velocity of a moving conductor in a magnetic field by the law of magnetic induction the voltage output with respect to frequency is constant.
This is the reason they are so good at high frequencies. Displacement of the ribbon is very small so there is no distortion. And they can handle the great sound of cymbals as for example the STC 4038s used by Alan Parsons on Dark Side of the Moon - Pink Floyd for drum overheads.
But when we sing close to them proximity effect increases the velocity at low, low mid, mid frequencies and output increases making them sounding dark.
An inductor in parallel with the mic does the trick of inverse compensating this effect (Pleiades filter).
And the filter can be chosen or adjusted until they sound flat for any particular distance.
See next post on how to equalize the Grampian GR1/L.
An inductor in parallel with the mic output is used on many world class directional microphones for low cut or high pass (making the resultant frequency response flat) such as the RCA 77DX, Electro-Voice RE15,...
References:
Microphones - Borwick
RCA 77DX manual
Electro-Voice RE15 manual
What is the mic used on Castle in the Snow - Kadebostany?
Could it be a Beyer M88, is this the mic seen live?
Or could it be a Beyer ribbon handheld mic?
Shouldn't these things be written on credits?
A great advantage of 25 ohm microphones
Is that we have direct access to a low thermal noise low resistance voice coil.
State of the art electron tube (or JFET too?) pre preamplifiers and nanocrystalinne cores for input transformers permit a direct connection to the grid through just one low turn ratio transformer. For example a 1:10 ratio transferring 25ohms to 2500ohms. (The impedance transformation ratio of transformers is the turn ratio squared).
Whereas with 200ohm microphones (assuming they do not have an internal transformer to step up 200ohms) it is again almost impossible to connect directly to the grid. Again a transformer should be used although it can be of smaller ratio if the pre preamp has a very low equivalent input noise resistance.
Some microphones, some very successful ones, have an internal transformer to get from 25ohms? to 200ohms. So another external transformer may then be used making the count of transformers before the grid 2. This may even be a good thing. Signal transformers are miraculous devices. They may make the sound better to listener's brain. Is this because of gentle roll offs that make the frequency response flat from producer's brain to listener's brain?
Would it be better or worse if the voice coil of an SM57, Unidyne III etc assuming it is 25ohms is accessed directly? Then an external (one only) transformer can step up to 2500ohms. This 2500ohms output impedance can be connected to the 2500ohm equivalent input noise resistance of the grid of the EF183 battery operated of a Pleiades low noise pre preamplifier. The input impedance of the EF183 at the Pleiades V6 conditions is 100Kohms so the microphone will not be loaded for worse or better. The primary turns of the input transformer will adjust for proximity compensation. How would this setup sound like?
Of course the Unidyne III has an additional high Z internal transformer winding which can be connected directly to grid. It is a high ratio which may roll off some HF which may be a good thing. Bass compensation can be made by adjusting the coupling capacitor to grid or connecting an inductor (Pleiades filter) to the 200ohm winding or a much larger one to the hi Z winding.
References:
Flat frequency responce form actor's, singer's vocal chords to listener's brain, Sound picture recording and reproducing characteristics - Loye, Morgan - Journal of the Motion Pictures Sound Engineers
Pleiades V6 schematic
A very interesting looking microphone book, Witnesses of Words - Hoeven
https://www.witnessesofwords.com/en/
Is the Quality of the prepreamp that dictates the quality of the whole system?
Great voice coil and ribbon microphones exist. How about prepreamps?
Classic condenser microphones almost get away with it as they usually have a superb quality internal prepreamplifier.
Is the quality of the prepreampifier, the quality of the rest of the system?
To listener's brain.
Songs that get air played are few. And most of them if not all have top quality vocals.
There are many U47, M88, 77DX etc.
But few hit songs.
Apart from the song and singer's ability could it be that the secret was in the pre preamp?
It is perhaps the only equipment that can be relatively easily handmade and of top quality.
The open source Pleiades V6 pre preamplifier is such an attempt. It is based on U47 but the hassle of the power supply is eliminated by a few Mohm resistor from anode to grid making operation of the electron tube possible with just a battery. The transformers are relatively easily wound on Magnetec 070 Nanoperm magnetic ring cores.
A great prepreamp may not be a commercial equipment. If it were perhaps thousands thousands of producers would produce top vocal sound.
But only a few do on the whole planet.
What is it that makes the vocal so good on Eternal Flame - Bangles ? Apart from the top intune singing and varispeed (a help for intune singing should be low acoustic monitoring level of the song on the singer's ears, as pitch perception depends on acoustic intensity, S.S. Stevens).
References:
Sound and Hearing - S.S. Stevens
Neumann U47 schematic
Pleiades V6 schematic
For varispeed see Michael Tretow interviews on how he recorded ABBA, or Mike Oldfield on his visit to the BBC Radiophonic Workshop etc.
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