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Old 29th March 2011, 07:23 AM   #1
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Default 6N6P at very low voltage

Hello all,

I'm in the mood for a new project, an hybrid power amplifier with tube frontend and solid state VAS + AB output stage.
The output stage is quite classical, as the VAS stage; they are both derived from the symasym project; what I'd like to make different is the frontend, with a tube LTP.

Now, my doubts:
I have a lot of 6N6P russian tube, and I'd like to use two of them for this amplifier; but I'd alos like to kep the voltage for the frontend as low as I can, in manner to do not stress too much the little silicon bugs...
So my thought was to use about 50V as the anode voltage for 6N6P, anda very low current, about 5mA.

Do you ever tried to use the 6N6P as such a low voltage/current? I've used them happily at 120V/23 mA, absolutely amazing.
Looking at the datasheet it seems the tube can work at such a voltage/current, but I have no idea about how it sounds.

I simulated the circuit in LTspice, and it simulate very well.
But how will sound in reality, in your opinion?
If for you it is OK to proceed, I will draw and etch two PCB for it, and try it on my test bench in the next weeks.

IF 6N6P are not suitable, which other cheap (russian) tube would you suggest (6N1P, 6N23P)?

Please find here attached schematic and simulation file.

Ciao,
Giovanni
Attached Files
File Type: pdf Hibryd_008.pdf (32.3 KB, 252 views)
File Type: txt Hibryd_008.txt (29.4 KB, 41 views)
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Last edited by croccodillo; 29th March 2011 at 07:35 AM.
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Old 29th March 2011, 08:23 AM   #2
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I believe 6N6P will work at 5V as well... But 6N30P will better satisfy your requirements.
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Old 29th March 2011, 03:21 PM   #3
mwiebe is offline mwiebe  United States
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Giovanni
I’m running a pair of 6N6P at 55V on the plate to ground, and 2.2V on the cathode to ground. 550 ohm cathode to ground resistance, so about 4ma plate current. They sound better in my circuit than a 6N27Ps did. They are drivers in a direct-connect P-P amp.
Matt
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Old 29th March 2011, 04:08 PM   #4
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Quote:
Originally Posted by Wavebourn View Post
I believe 6N6P will work at 5V as well... But 6N30P will better satisfy your requirements.
Do not buy 6N6P-I in nice boxes or without them, even if they are in stock of audiophile shop in Vienna, like i did.. They are not for audio and after few days of getting use to them your ears will confirm that. Just plain 6N6P will do the work much better.

Anatoly. Hi. I enjoy reading you for quite some time. I couldnt agree more, that specific sound of the tube is an myth and that sound of it depends from much other factors- from one amp, to another.
Some slavic souls in strange way likes myths and tzars, they also like in the same way their village gubernators and then their countrymen are paying dearly for that perverse type of worshippery.
In book of Švejk adventures there is an episode...He was really funny guy. But. His times were hard.
Švejk was stealing dogs of mixed breed, "tunning" them to look like pedigree ones, falsificating pedigree papers and after that selling them as real ones.
Audio myths makers are sometimes quite similar to Švejk.
Also people who are rebranding tubes.

Best regards, Jaro
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Old 29th March 2011, 05:11 PM   #5
Helmuth is offline Helmuth  Netherlands
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The hybrid is reverse the end-stage shout be tube's.
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Old 29th March 2011, 06:57 PM   #6
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Quote:
Originally Posted by Helmuth View Post
The hybrid is reverse the end-stage shout be tube's.
I've found that the best tubes for end-stages are Semisouth JFETs.
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Old 29th March 2011, 06:57 PM   #7
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Quote:
Originally Posted by Helmuth View Post
The hybrid is reverse the end-stage shout be tube's.
What do you mean?
What I intended is that I would use both of the two world, the "glass" one and the "silicon" one (actually, where's the difference? both are made of silicon ), so my amplifier would be an hybrid of those two worlds.
If I'm wrong, please explain.

Quote:
Giovanni
I’m running a pair of 6N6P at 55V on the plate to ground, and 2.2V on the cathode to ground. 550 ohm cathode to ground resistance, so about 4ma plate current. They sound better in my circuit than a 6N27Ps did. They are drivers in a direct-connect P-P amp.
Matt
Thank you very much, Matt; actually what you've done is exactly what I've in mind: a tube differential pair driveing a PP output stage, directly connected!
[EDIT: Not exactly the same topology, but actually the same idea, driving transistor/mosfets with a tube]

This makes me happy; I already own at least 10 6N6P, so I can use them happily!

Quote:
Do not buy 6N6P-I in nice boxes or without them, even if they are in stock of audiophile shop in Vienna, like i did.. They are not for audio and after few days of getting use to them your ears will confirm that. Just plain 6N6P will do the work much better.
Absolutely right! I have plain 6N6P, coming directly from Russia; a very lovely tube.

Tomorrow morning I will begin drawing my PCB for the amp.
I will be back soon with the PCB, asking for your comments about it.

Thank you very much to all of you.

Ciao,
Giovanni
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Last edited by croccodillo; 29th March 2011 at 07:05 PM.
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Old 29th March 2011, 09:59 PM   #8
Bigun is online now Bigun  Canada
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Quote:
Originally Posted by Wavebourn View Post
I've found that the best tubes for end-stages are Semisouth JFETs.
but I don't think you can get n-type and p-type pairs and the poster wants push-push no ?
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Old 29th March 2011, 10:16 PM   #9
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Quote:
Originally Posted by Bigun View Post
but I don't think you can get n-type and p-type pairs and the poster wants push-push no ?
No problem for that: I've already decided for the output devices, I have already on hands a few 2SK1058 and 2SJ162.
Actually, I have all the active device (6N6P, 2SC2240, 2SA970, 2SC2911, 2SA1209, 2SK1058, 2SJ162) in my junkbox, collected from previous projects; I decided to build this amplifier because I-d like to use what I already have.

But the Semisouth JFETs (which I didn't heard of before) sound very promising; maybe, next project...
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