Most Exotic MM phono preamplifier

[kuroguy]

If this is just about posting pictures,we have a sticky thread for that. Otherwise, this is just the emperor's other new amp.

 

[petavgeris]

I'd like to see a schematic diagram to see how it works.

Hello from Athens!
I could draw the schematic of this amplifier but IMHO there is absolutely no need for it. The reason is that the circuit is so simple that is easy to describe without mentioning any schematic or diagram.
There exist four HV power supplies, one per each D3A tube, and four filament supplies accordingly. As soon as on this preamp I have not applied any active regulation, it could be very easy for anybody to 'capture' what is done here.
Each HV supply consists of one HV transformer and one double pi filter. The chokes are of more than 300 Henries of inductance each and the capacitors are 10-47-1000 uF.
RIAA is of course passive between the stages. Both tubes are anode driven without phase reversal from input to output. Both tubes are inductively loaded by means of interstage/output transformers and are self-biased at 28-30mA of current at 130-135V between anode and cathode.
For anybody out there that would like to experiment with this phono preamp design, I have to double underline that it is absolutely impossible to design and implement a stable circuit without using dedicated power supplies. That means separate rectifier tubes and separate HV transformers. Otherwise the circuit oscillates due to poor low frequency rejection. Here you have to get rid not only of 50 Hz hum but of extremely low frequencies even at fraction of one Hertz, as the phono cartridge easily captures them and then the amp amplifies this signal at an enormous degree.

 

[Gluca]

your craftmaship is impressive! congrats!

 

[petavgeris]

your craftmaship is impressive! congrats!

Thanks a lot!

Some specs now.

• Class A MM phono preamplifier without feedback
• Two stage design, anode driven tubes, inductively loaded
• Gain: 45 dB @1kHz
• RIAA equalizaion curve is performed RC passively (LCR RIAA has been intentionally avoided due to worse sound performance)
• Input impedance: 47 kOhms
• Output impedance: less than 430 Ohms
• Frequency response: 8Hz-70kHz @-3dB
• Independent HV and filament power supplies per each tube with double pi filter
• Tubes complement: four Siemens D3A pentodes wired in triode mode and four vintage Telefunken RGN4004 rectifiers with black mesh anodes
• Tubes biasing: 28-30 mA @ 130-135V, self-biased
• Three chassis and twenty four iron pieces per stereo 'set', all designed, calculated and handwound by myself, specially for this phono preamp design (2x IST, 2x OPT, 8x HV supply chokes, 4x HV t/f, 4x RGN4004 filament supply t/f and 4x D3A filament supply t/f).
• For all iron pieces, I have used the custom ordered supreme ferromagnetic material in form of tape wound cores (c cores throughout).

Some lovely fellows of a local audiophile community have asked for further information, on how it is possible to obtain a combination of such a relatively high gain and relatively low output impedance using only two active stages. The answer lies in proper tubes selection and proper inductive loading calculation, it is nothing that extreme or supernatural, plain physics.

 

[Vinylsavor]

Hi!

Congratulations on this phono stage! Very beautiful craftsmanship.
The D3a is a great tube for phono preamps.

Do you use RC RIAA or LCR RIAA?

means of interstage/output transformers and are self-biased at 28-30mA of current at 130-135V between anode and cathode.

Any reasons for this particular op point? I prefer the D3A at less current and slightly higher plate voltage to get bias voltages in the range -1,3 to -1.5V. I try to avoid bias voltages lower than -1V

I have to double underline that it is absolutely impossible to design and implement a stable circuit without using dedicated power supplies.

I have built several D3a phono preamps with common supplies and have not encountered instability issues. Of course each stage needs proper decoupling and I do it passive as well. I also like large inductance chokes for this.

I don't see the advantage of independent heater supplies for each tube. Indirectly heated tubes are very uncritical in this respect and I also don't see much of an interaction through the heater.

Best regards

Thomas

 

[Vinylsavor]

Hi again,

[*]RIAA equalizaion curve is performed RC passively (LCR RIAA has been intentionally avoided due to worse sound performance)

I see you answered that already. I am surprised that you liked RC RIAA better. I routinely build phonos with both RC and LCR RIAA. LCR always wins in terms of sound performance by a big margin. What kind of LCR network did you try?

Best regards

Thomas

 

[petavgeris]

Hi!

Congratulations on this phono stage! Very beautiful craftsmanship.
The D3a is a great tube for phono preamps.

Do you use RC RIAA or LCR RIAA?




Any reasons for this particular op point? I prefer the D3A at less current and slightly higher plate voltage to get bias voltages in the range -1,3 to -1.5V. I try to avoid bias voltages lower than -1V

Best regards

Thomas

Hello Thomas.
Thank for your comments!
What a coincidence! I tried to avoid biasing lower than 1V as well! Cathode resistor is 39 ohms, so biasing voltage is 1.09-1.17 V!
Regarding LCR, it sounds smoother than RC and this is what I would prefer to avoid. Sound is more immediate and punchy with RC RIAA. L suffers a lot and sounds far worse, at least to my ears, probably because AC signal is very weak and the inductor has a core, so the magnetic hysterysis plays a major role here...
LCR is not an option for me, but I would like to evaluate pure LR RIAA. This is a very difficult design, as I always avoid running L without DC biasing.
Regards,
Peter

 

[Vinylsavor]

Hi!

LCR, it sounds smoother than RC and this is what I would prefer to avoid.

Don't give up on LCR. In my experience it does not necessarily sound smoother, at least not in a negative way. Well implemented LCR phono stages excel in terms of higher resolution and especially improved (more natural) articulation of voices.

Best regards

Thomas

 

[petavgeris]

Thanks for your comments Thomas.
I know that you're a great designer and I always keep in mind your advice.
In LCR I listen something that reminds me of TVC sound and I really try to avoid it.

 

[Erik van Voorst]

I enjoy your builds...I hope you ignore the jealous remarks...
I get lots of them but that stays a small percentage of the forum crowd....

Great fun this phono amp...if I recall there was a japanese small company who did something simular......at least size and trafo wise....

The price was staggering for the phono pre...a 100.000 or so, if it gets sold he must do something right

Edit

Yepp dual mono phono stage 150.000 dollar

................Like William Zane Johnson of Audio Research here in the U.S., Mr. Imai is a doyen of handcrafted tube amplifier and preamplifier designers in Japan. Indeed, one of the many enticements for going on this trip was the chance to hear Mr. Imai’s now-$150k TEA-9501 dual-mono phonostage preamplifier ..........

 

[petavgeris]

Thanks a lot Erik.
I enjoy and I love creating exotic audio amplifiers, it is my passion of life. It is a one man show, not a formal business involved here, and you are right, the cost for each triad of chassis exceeds $100k ($110k).
Whoever claims he has really done or listened to something similar, I am here to invite him for a personal listening session. Both the level of performance and selling price are stratospheric and this one is the second set. Both two stereo sets are already sold and I am now making plans for the custom c core pieces of the next two sets.
Thank you for your kind words.

 

[JZatopa]

I wish you were on this side of the pond, I would love to hear some of your pieces.

 

[petavgeris]

I enjoy your builds...I hope you ignore the jealous remarks...
I get lots of them but that stays a small percentage of the forum crowd....

Great fun this phono amp...if I recall there was a japanese small company who did something simular......at least size and trafo wise....

The price was staggering for the phono pre...a 100.000 or so, if it gets sold he must do something right

Edit

Yepp dual mono phono stage 150.000 dollar

................Like William Zane Johnson of Audio Research here in the U.S., Mr. Imai is a doyen of handcrafted tube amplifier and preamplifier designers in Japan. Indeed, one of the many enticements for going on this trip was the chance to hear Mr. Imai’s now-$150k TEA-9501 dual-mono phonostage preamplifier ..........

Audio Tekne is the company.
I know little about this phono preamp, besides its stratospheric price.
The only thing I know is that Mr. Imai does not believe in SET but only in Push Pull. While some things are promising in PP design (less overall harmonic distortion but worse distribution of harmonics, higher power output, much less cost, etc), I can easily prove in terms of laws of nature (electromagnetism) that SET still remains the pinnacle of design for audio applications. PP properly elaborated remains a good alternative though.

But SET with Directly Heated Tubes throughout still remains something unique!

 

[Cassiel]

I also have kind words somewhere but the day I posted I was feeling a little 'funny'. A lot of work but hey no problem because you did enjoy it. That's the most important thing. Oh and others appreciate it as well, that's the second most important thing.

 

[Erik van Voorst]

Audio Tekne is the company.
......., I can easily prove in terms of laws of nature (electromagnetism) that SET still remains the pinnacle of design for audio applications........

Not want to discuss but my personal believe is that listening is sometimes an entirely other matter than measuring..so I am very careful in judging other components be it amps, cds, speakers....

Sometimes the specs get me prejudiced and I in the end I have to eat my words cause the thing sounds amazing...
Sometimes I listen to a near jitterfree cd transport and it does not make music..it does not "sing".. C

 

[jacco vermeulen]

the jealous remarks.

You forgot the beaaaaautiful turntable.
Audio Tekne - Record Player ACP-8801 NEW - YouTube

You guys are nuts (you too, Mr. van Voorst)

 

[nhuwar]

Nice job Peter. I wish I could wind my own like you do. Maybe someday I'll try.

I bet the only bad thing about that phono preamp is moving it, lol. But you don't need to do that much.

So what is next to build, a line stage?

do you have any under chassis photos?

excellent work.

 

[petavgeris]

Nice job Peter. I wish I could wind my own like you do. Maybe someday I'll try.

I bet the only bad thing about that phono preamp is moving it, lol. But you don't need to do that much.

So what is next to build, a line stage?

do you have any under chassis photos?

excellent work.

I will be back. Please give me some time because I'm in a hurry.
All the best.
Peter