Adding 2 sigbals with hybrid transformers while DC current of feeding anode circuits cancel

For example amplifying each mic with an 1H4 electron tube (Pleiades V6 1H4 or CV2269)and use the hybrid transformer as an output transformer for both electron tubes, like on push pull circuits. Inspired while watching the EMI REDD.37 and REDD.51 block diagram while thinkimg of the Kimball mixer in the cinema Engineering book or the Elements of Sound Recording - Frayne, Wolfe books.

The ultimate mic preamplifier low noise test?

Caution: At your risk, this must not be attemped unless there is a limiting protection on the headphone circuit otherwise irreparable ear damage may result. When the microphone preamplifier is very low noise such as the Pleiades V6 1H4 open grid...When the mic is connected out of phase and the mic is aproached: to the Sennheiser HD580 headphones, ambient noise cancels out and at the partucular ear it sounds as if silence is sucked out. Caution: if mic is in phase, ambient noise increases and there is possibility of positive feedback which may damage hearing unless a limiter is in circuit.

Open base transistors

A common emitter Pleiades Siemens AC151 germanium one transistor microphone front end preamplifier was made on S-DeC projects breadboard. Signal path: male singing voice in reverberent room - Revox M3500 - German 500 ohm to 600 ohm low inductance input transformer for isolation and low cut - phase inversion adaptor - 56nf to base - Pleiades amp with Siemens AC151 with Rc=5K6, R(Vb to base)=1Mohm, Cc=220nF, Vb=9.3V, emmiter to ground +, Realistic 32-1101A disco mixer line in or mic in = Sennheiser HD580 - Singer (listener) brain. At such conditions Vc drops to 3.5V. It is noisy, hissy. When the bias resistor was removed ie base floating, gain was reduced, but noise improved, input impedance must had increased and fat nice sounding distortion took place making vocals sound airy and big. At such open base conditions Vc=8.2V, so drop across load resistor is ish 1V and from Ohm's law Ic is ish 1V/5.6Kohm ish 1V/5Kohm ish 200 microampreres.

Some videos have been uploaded on Vicky Moriton channel YouTube

Everything in music?

How music works YouTube Vicky Moriton Channel https://m.youtube.com/watch?v=zOZabr37iF8

Is the best sounding microphone preamplifier the one we made when we were kids?

Although I had used a electronic constuctions game called Polycyclomatic 1002 or 501, see for example page 31 on a different game called Philips 40, www.lushprojects.com. Excellent microphone amplifier operating in class A ie electrons flowing all the time while dancing to music.

Very ofter there is no more than 4 notes sounding together in western music

Listening for example to a good song or listening or reading the score of a nice symphony. For example when harmony is F major 3rd major 7th there are many F A C E played on various musical instruments at different registers or octaves.

How would a one stage Pleiades germanium transistor microphone preamplifier sound like?

A Siemens coincidence

Last Wednesday listened with Vicky the Siemens WSW mic preamplifier on youtube. On Thursday while looking for ferite ring cores on Dimoulas shop for input or output transformers, Sylvia gave me the Siemens vintage catalog including ferrites, Mikes Psalidas must had used this on Finos Film console filters as he had show me non ring ferite cores, and Finos studios was a few meters away from Dimoulas shop. On Friday while looking for germanium (high electron mobility) transistors Kostas gave me 2 Siemens hearing aid mic preamps. Same day at Sideris shop a tiny Retex ABOX, palm size with beize brown colors was found as well as some germanium transistors.

How would a tiny adding console with class A operating battery tubes or transistors look like on the smallest Retex ABOX?

On a microphone chain 1st gain control (attenbuation) should be at least after 1st active device amplifying stage, for avoiding overload?

Patent US3090926A on very low voltage germanium transistor eg. OC59 amplifier for hearing aids microphone preamp etc , uses a tunnel diode

Frequency response of the Pleiades V6 CV2269 electron tube mic preamp

This is possibly world's first pocket box electron tube microphone preamplifier operating directly with an AAA 1.2V battery derived electric potential for both heater and anode. Frequency. With the Freed variable inductance input transformer and a few feet output cable the frequency response is -10dB at 100Hz and 20KHz creating an unboomy natural vocal sound to listener's brain. There is also +2dB at 2KHz, +3dB at 3 KHz, +2dB at 4 KHz, +1.5dB at 5 KHz, -1 d at 8 KHz. So excellent vocal presence too to listener's brain. Excellent graduall electron tube overloading. Frequency response is simmilar to EMI REDD.37,.51 EQ settings, see Recording the Beatles book. It was firstly used on the song Tezcatlipoca - Ira, George.

The Pleiades K177 JFET microphone prepreamplier possibly needs a drain to ground resistor for mic transformer protection and electrical damping

Can Quantum Entaglement experiments be made with aperiodic PI Pythagoras number used as random generator?

Discussed this with Vicky while watching the relevant Horizon BBC program produced by microphone book author Alec Nisbett. (Alec Nisbett's name was seen on the Tascam 244 additional information notes on further reading. Bravo to Tascam.)

How would music made by Pythagoras PI sound like?

For example using the endless unrepeatable 3.1415... to dictate notes. Eg Mi Do Fa for 3 1 4 ... (Discussed yesterday with Vicky).

How can this great snare sound that we hear on great records be made?

One way is by overloading simple class A transistor amplifier common emitter circuits. See previous posts. The unprocessed snare sound from the Alan Parsons sound check 2 CD, sounded more like Everybody Wants to Rule the World - Tears for Fears

How would the 2 transistor microphone preamplifiers sound if the feedback resistor is removed?

Without negative feedback distortion would be less abrupt, ie gradual distortion of more pleasing low order overtones. For example removing or increasing the 2nd transistor collector resistor to emiiter of 1st transistor on the electronic kits mentoned on previous posts. These simple class A (electrons flowing all the time) circuits are based on the Mullard book examples. References: 1. Tubes vs Transistors, is there an audible difference - Russel O. Hamm - JAES. 2. Transistor Audio and Radio Circuits - Mullard

P&L Electronics, iincluding audio kits with descrete transistors

For example kit no 300, microphone preamplifier with 2 transistors. PNP BC560 direct coupled to NPN BC550. Similar idea to the UHER 4200 preamplifier. Designed by Loucas Papatheou. Visited the shop and met George. www.papatheou.gr. They also sell a very interesting moving magnet record player cartridge RIAA 2 transistor preamplifier, similar to the Smart Kit 1023 kit. Thanks to Vagelis at Radio Kalithea shop who reminded of this shop after so many years.

On the previous experiment Sowter 8650a output transformer was used after Smartkit 1024 and before Sennheiser HD580

Overload behaviour of 2 transistor Smart kit 1024 microphone preamplifier driven by Alan Parsons Sound Check 2 CD while driving headphones

Signal path: various test CDs - Sony CD Walkman - Solartron dB attenuator - Smart Kit 1024, R1=0Ohms, Vb=9V or 18V. Enjoy the Silence - Depeche Mode sounds big but not as airy smooth as on Pleiades V6. 1 KHz reference tone from Hitech magazine CD clips rather abruptly, within 1 dB input increment, posibly due to the negative feedback circuitry. Alan Parsons CD: Clipping behaviour of: Tenor, Soprano, Piano unacceptable, Male Rock Vocal nice, Guitars great, Electric guitar amazing distortion, Bass Guitar amazing sound, Flute amazing, Saxophone unbeleivable overtones, percussion poor, Kick Drum amazingly big, Snare Drum amazing crispness, Cymbals, Hi Hat big sound with distortion, Toms unbeleivable especiall bass tom sounding 10x bigger, deeper, Violins, cellos, Woodwind crap distortion, Orchestra String Music Track with boosted airness, Organ bad distortion. How would Pleiades Darlington mic preamp compare?

Driving headphones with the Pleiades V6 1H4 microphone front end

Signal path: Enjoy the Silence - Depeche Mode on CD - Sony CD Walkmman at line out - Solartron laboratory step db attenuator - Pleiades V6 1H4 open grid Va=1.3V, Vb=12V, Altec input and output transformers = Sennheiser HD580. It sounds like a crystal palace of full bandwidth. Slow recovery of gain reduction (when overloaded) from limiting due to rectification effect due to open grid, distortion somewhat interesting.

To add signals before or after the mic preamplifier? Or leaving God to combine signals in air and use just one microphone?

How to connect up the EMI RS106A for variable slope frequency arrenuation?

It is mentioned in the book Recording the Beatles that the central attenuation knob varies the frequency attenuation slope!

A portable mixer based on EMI REDD.37 ans Smart Kit 1024, 1126

Discusused briefly with Alexandros who co-suggested series variable resistors after the mic ie before any active stage like EMI Germany conceived REED consoles in order to have an almost infinite dynamic range. Passive EQ after the mic or before any active amplifier device. How would it look inside a pretty Retex ABOX small console box? Adding done too before any active device, BBC way! (reference: High Quality Sound Production and Reproduction - H. Burrell Hadden, BBC)

3 stage amplifier from microphone to headphones

For example (any battery connected in series with suitable fuse): Revox M3500 - Pleiades V6 1H4 electron tube battery powered mic pre preamp with Altec input and output transformers, Va=1.2V(AA rechargeable battery), Vb=12V(garage remote control battery) - Smart Kit 1024 2 transistor BC550C mic preamplifier, R1=0Ohm, 9 Volt battery - Canford red high Z to low Z transormer inside Red sleeve Neutrik mono jack male connector - Sennheiser HD580

A very nice transistor vocal signal path

Example: Elfie - Bacharach - male voice - Revox 3500 at 10 in - German e+p signal transformer of inductance ratio 232mH:280mH for bass heaviness cut - Western Electric 1H:4H input transformer for further impedance setup - Smartkit 2 BC550C mic preamplifier with R1=ohm ie Vb=9V - Realistic 32-1101A Disco Mixer tape in - Sennheiser HD580 - listener's ears , brain (it sounds like good quality vocals reproduced from a good vinyl record)

The great recording acoustics of good stairways

At your risk.

Great looking console boxes for mixers ie adders etc from Spain, www.retex.es

ABOX series enclosures.