Updates to the Pleiades DL94 single electron tube battery powered audio power amplifier operating in class A1

 

At your risk. Lethal voltage present.

Five rectangular holes have been created by a jewelers saw for housing five 2 x 9V batteries for a Vb of 90 volts. 

All 5 Bulgin battery holders will be at the back of the diecast aluminum box. Then the output transformers then each DL94 for each channel and then the step up input transformer for each electron tube.

In the front will be a Bulgin holder for 2 AA batteries for the direct heated cathode voltahe Va, and a battery holder of AA size for the -6V Vc bias.

This amplifier is using no resistors or capacitors, like the original Harold Arnold 20's patent of the use of thermionic currents...

Please visit older posts for more details.

 

Other single transistor amplifier circuits

 

At your risk. Please take all safety precautions. A suitable fuse always in series with a battery to prevent burn injury or fire hazard. in this case a suitable fuse (200mA?) will prevent your speaker from blowing in case of thermal runaway etc. 

These amplifiers are similar to the Pleiades 2N3055. Now usually an air gaped output transformer is used but the second schematic is what was simplified from the book Amplifiers by Jones. There is also a very interesting book Transistor Amplifiers for the home constructor by SIr Clive Sinclair who is also behind the famous ZX Spectrum home computer.  

One of  first listening experience with such an amplifier was with just a 2N3055 fed by the song Is it a Crime - SADE from CD, the amp feeding a SONY APM speaker with just a low cut capacitor from the paper cone tweeter. Jaw drop mode. When Vicky first heard this amplifier on Constant Craving - K.D. Lang she could not believe this fabulous sound was coming from this small mess of wires on the floor and one transistor cooled by a French wrench. She still calls this amp the French wrench amplifier.

With just one amplifying stage here is only one set of distortion products and you may be in the league of the Neumann U47 with its amplifier of one VF14 electron tube. 

Marios from the photocopy shop told me that this great sounding PC USB powered Fujitsu Siemens speakers from the 90's may have just one transistor inside for each speaker.

By doing a search on google for "90's usb powered pc speakers one transistor amplifier schematic"...

https://forum.allaboutcircuits.com/threads/simple-pc-audio-amplifier-circuit.109732/

Life is good!

Why does pitch change with change of intensity?

 At your risk.

For example playing a 440Hz louder gives the perception of a lower pitch.

Why?

Not clear to me.

A piano can convert frequency to distance. For example by pressing the right pedal we leave all strings undamped. Then then if we whistle for example, the higher the frequency the more to the right strings are vibrated by resonance.

The basilar membrane converts frequency to length. 

Is it a nature's way of protecting the ear? Pitch change by stimulus intensity preventing the same hair cells being fired  along the length of the basilar membrane?

Is the change of position at the basilar membrane due to some non linearity in amplitude response. creating a DC offset?

Similar to demodulation of AM signals by the rectification effect of a diode?

(Side chain signal of a compressor created by diode rectification? Does the movement of the 3 tiny bones in the middle ear play a nonlinearity part too?)

Similar to DC bias change of single ended amplifiers with cathode current bias, RC (cathode resistor).

Similar to expansion in solids by temperature increase, there is nonlinearity in the vibration of molecules, the displacement to the right is higher that the displacement to the left.

Handbook for Acoustic Ecology

 At your risk.

https://www.sfu.ca/sonic-studio-webdav/cmns/Handbook/

Pitch

 At your risk.

https://www.sfu.ca/sonic-studio-webdav/cmns/Handbook/Pitch.html

Pitch Change of tone of 440Hz by changing the intensity

 At your risk. Please keep volume down to protect your ears especially if using headphones.

By comparing soft volume to higher volume, the higher volume sounds to me lower in pitch.

As loudness tends to zero pitch becomes maximum.

How about you?

The fact that i hear a lower pitch makes me sing along a note of lower pitch. 

This (even if it is a small difference) is important because it makes a singing note sound really bad and out of context with the music or backing track. For example annoying beats could be created.

Listening carefully to good singers, the very good world class ones, it can be heard that they too begin almost any note flat (below correct pitch) but then raise the pitch while the note sustains until it sounds correct. I tried this trick and my singing is so much better and enjoyable. I try to correct almost every note.

Psychoacoustics - Pitch Perception

 At your risk.

Vocal Exercise from real well known beautiful Song melodies

 At your risk.

For example closed lips 3:36 to 3:42 on Such a Shame - Talk Talk

Instructor can play figured bass E, then E6 then D, that is E G B, E G C, D #F A, while student can sing the beautiful melody with the nice glissando.

Then transposing a semitone up etc.

Such a Shame - Talk Talk

 

Update on the Pleiades 3 K117 battery powered JFET phono preamplifier

 At your risk.

If any of the two 9V batteries is discharged the preamplifier goes into motorboating oscillation.

Possible cause the increased internal resistance (ie output impedance) of the battery creates voltage drop at the first stage from the current drain of the other stages. this is equivalent to an input signal or really positive feedback signal. If series resistors and then capacitors to ground for each stage were used this could solve or reduce the effect but it is decided not to use any of them.

The battery or batteries should be replaced anyway and this is a sure sign to do so.

As a remix of Such a Shame - Talk Talk was being reproduced suddenly the beat was modulated in amplitude by this very low frequency. It was thought as a production effect and may be used as such. A very interesting stereo tremolo effect. The subsonic frequency may damage equipment or ears so please keep the volume down. If the volume is already up before the batteries are exhausted it can be dangerous.

 

The simple melody Love on previous post can also be called All My Love

Why are some songs often played on the radio, the vocal pitch increase trick for almost each note

 

At your risk.

i have the impression that a good singer may be doing it consciously. Now that i know it i can hear it if i concentrate on the part of each note after the attack which for some reason may be wrong (flat ie below correct pitch) even for the best singers. Is it how our mind works?

What ever the reason if we concentrate on correcting the poor note the feedback mechanism we create gets it right by subtle glissando. Cybernetics in singing. 

For example the first "me" at 0:20, in phonetics notation, mi: or mii the second i is clearly higher so that the singer and listener's mind is happy.

Examples are everywhere on radio but these 2 were heard today on Rock FM in Athens, Hellas.

Another example, i can not remember on which FM radio station it was heard a few days ago:

i heard about this trick from a serious looking intelligent person while i was doing my military service, long time ago. i could not really believe what he was saying. It took me many years to digest and rediscover.

It surely helps me enjoying singing.

Of course there are many more elements that can make a song liked, please see for example Hit Song Ingredients - euroelectron.

Love, a simple melody with nice chords in F minor key

 At your risk.

F minor is a very beautiful sounding key. For example:

Almost accidentally both pay buttons were pressed and a mush up was created.

The simple melody of Love was somehow inside me perhaps after listening to the radio, or after feeling something for sometime. By playing on the Pleyel upright piano some of the beautiful chords defined by the key of F minor were asked for to be used. The chord defined by bass bD, bass F, bE, bass bB.

The code (Bach's figured bass notation) of the chords is bD7, F, bE6, bB79.

So together with the melody.

-   -   F   -                         D7

A  -   B  C

o   -   -   -                          F

-   -   C  G(down)

o   -   -   -                           E6

-   -   C   B

o   -   -   -                            B7 or B9

-   -   -   - 

repeat

please remember the key signature of F minor, all A, B, D, E are flat so for example bD7 is played bass bD with chord F bA C ie bDmaj7. ANd of cource the melody notes are F bA bB C....

The symbol o means that the note carries on.

The symbol - means pause of 1/8. So each chord lasts 8 beats of 1/8.

The title on the cassette demo is love with another 2 words, not currently remembered.

 

  

A battery powered high quality sound reproduction system from phono cartridge to loudspeaker

At your risk. Please take all safety precautions. A battery must be connected in series with a suitable fuse to avoid skin burb in case metal jewelry is worn or avoiding fire hazard.

This system combines previously described Pleiades amplifiers.

It was put up together today for the first time with phono channel out of phase connection corrected and with the RIAA cooking corrections in order to correct overal preamplifier response as described on previous posts.

Preamplifier and power amplifier are operation in class A (electrons flowing all the time, even when there is no music playing).

Total number of transistors used for each channel is 4, 3 K117 JFETS for the preamp operating in low gain with local feedback (source resistors unbypassed) and one 2N3053 on very small heatsink for the power amplifier with zero negative feedback.

Both the phono preamplifier and power amplifier have an output transformer. The power amplifier has a relatively small ferite output transformer with air gap separating the 2 E sections as there is DC current flowing in the primary. Toilet paper is used for the air gap and Siemens Es anre secured together with metal clamps fastened with bolts and nuts.

The DUAL CS-627Q direct drive turntable is battery operated too with same voltage as the power amplifier. 24V from two 1.2Ah powering both turntable and stereo power amplifier.

The hono preamplifier is powered by two 9V batteries.

Power consumption is very low, current consimption is about 20mA for the stereo power amplifier now than the ambient temperature is high, 14mA in the winter. The turntable consumes about 100mA. the phono stereo preamplifier about 2 mA. So total power consumption is somewhat more than 2 Watts.

Power output should be of the order of 100mW yet it sounds surprisingly loud with huge bandwidth and no need was found in today's listening tests for higher volume in a small bedroom with speakers at about 2m or less from listening position.

Signal path:

CD or vinyl records - Sony CD Walkman D-EJ758CK or Dual CS-627Q with original Ortofon cartridge and new stylus - Pleiades 3 K117 phono preamplifier - Pleiades 2N3053 power amplifier - Celestion Ditton 150 loudspeakers - small room with 3 Pleiades membrane (bitumen felt) bass absorbers inside white painting stretched canvas frames of 3 different dimenssions 

CD used is The Year of the Cat - Al Stewart

Records used: Only Love LP - Nana Mouskouri

                        Brothers in Arms LP- Dire Straits

                        One Day in your Life 7" single - Michael Jackson

                        Take a Look - Natalie Cole double LP

The sound quality was amazing, breathtaking with huge bass, smooth mid and very extended treble about 3 more octaves than listening to YouTube, at least one more octave than listening to CD. About at least one more octave that listeningto other CD systems even very high quality ones yet without the harshness. 

Anbience sounded amazing.

And strings did not sound harsh at any time. This is possibly due to the fact that the passive RIAA filter comes immediately after the low gain 1st stage. Therefore clipping of the extreme content of high frequency due to preemphasis on records is avoided, see previous posts on the Pleiades 3 K117 design.

The whole system was exremely quiet no noise or hiss heard at any time even when volume control is at max and no record is playing.

Very impressive is how exteded treble sounded with no harshness, the deep bass and smooth liquid midrange.

The power amplifier is just one transistor for each channel.

   

Equal Loudness Curves can be translated as Καμπύλες Ισης Ακουστότητας

Ωκεανός - Ναντια Διολιντζή Lyrics, Γιωργος Τσακίρης music, Ocean - Nandia Diolingi, George Chakiris, elements of the song

In B minor.

Bossa nova.

Step down bass.

Bass Code (Bach figured bass notation):

B

A6

G7

F7

modulation to E Dorian

E

E46

Example melody with lyrics:

-   B   D   -            στα - γο           chords   (harmony) B D #F

B  -     -    A           να      πεύ-                    

o   B   ο    -            τω                                                  A  #C #F       

-    -     -    E          βυ-

F   D   B    ο           θί - ζο - μαι                                   G B D #F

-    -     -    Α           στον

-    Β    Β   Β          ω-κε-α                                          #F A #C E

Α    ο    Β   ο          νό σου

.   .    .

-   -   B   A              κρά -τα                                           E G B

B  -   -    A

o  o   B   o                                                                     E A #C

A simple MOSFET power amplifier with just a 12V battery, a potentiometer and resistor for bias, an input coupling capacitor and no output transformer

 

At your risk. It may blow your spekaer if  a protective fuse is not connected in series etc.

Please see previous post on Pleiades K951 amplfier with speaker connected directly to the drain of the MOSFET.

Update on Pleiades K951single MOSFET zero feedback single ended power amplifier

 

At your risk.

Today the bifilar 1:1 output transformer was disconnected from drain and connected to the source. This was done fairly quickly as all connections are done with Wago snap terminal connectors.

Source follwer configuration worked with change with readjustment of bias from the 50K potentiometer in series with 47K  but sensitivity was low as there is no voltage gain.

Signal path:

CD - SONY CD Walkman - Pleiades K951 as source follwer - Marantz Imperial 5C

So power suppling the speaker was low.

The amplifier was remodified to drain follower.

Then the output transformer was removed and the AKAI SR H-44 speaker connected directly to drain instead of a load resistor. This should not blow the speaker if drain currect (which now passes through the voice coil) is kept by suitable bias to up to say 300mA. It worked and sounded nice, but less loud than when using the output transformer due to loss of efficiency.

Betasilk or Betaplast etc

 

At your risk. This is not a medical or dermatologist advice. Betadine cream is not suitable for persons with thyroid problem.

Combining 2 products together to create a new product. 

Hansaplast with Betadine cream.

Hansaplast moistened with Betadine cream applied on skin spots may vanish the spot if applied overnight(s) or during the day. 

Betadine cream softens the spot until it breaks, it disinfects and the Hansaplast tisue absorbs.

Thsi idea comes from adapting my dermatolosgist Yiannis Peros' advice when I had a serious skin infection.

 

Merino Wool t-shirts

At your risk.

One of the best thing bought this year. Black long sleeved.

They are 3 times more expensive than cotton but they last at least 3 times more.

Minerva brand.

They keep you warm in the winter, dry on both seasons.

When the is heavy air conditioning in the summer, you are saved as you are dry before entering the air conditioned environment and you don't feel cold.

Dryness in the key.

And they feel compatible with one's skin.