Are you looking for 2A3 amp info or how to make pcb info? If it's amp, here is one I've built. It sounded good.
I would think it would be harder to build with a PCB, not as easy to make changes or upgrades to the circuit. I would suggest though if he wants to use the 6SN7 + 2A3 to do a cascaded 6SN7 into the 2A3, like the Sun Audio SV-2A3, and countless other 2A3's and 300B's.
If he can get his hands on some 12AT7's I would check out the Baby Ongaku. However, the 6SN7 + 2A3 would probably provide the easiest and cheapest path to success. I would avoid the PCB for such a simple design, but just my 2 cents.
Cheers
James
edit: If you want to use a PCB and you can get them shipped there you could look to the Tubelab SE, however it uses the 417A for input duties. (www.Tubelab.com)
If he can get his hands on some 12AT7's I would check out the Baby Ongaku. However, the 6SN7 + 2A3 would probably provide the easiest and cheapest path to success. I would avoid the PCB for such a simple design, but just my 2 cents.
Cheers
James
edit: If you want to use a PCB and you can get them shipped there you could look to the Tubelab SE, however it uses the 417A for input duties. (www.Tubelab.com)
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Here are a few to think about, Sun Audio is first
http://www.goodsoundclub.com/Site_Images/Sun-Audio_VT-2A3_3.JPG
http://www.jeack.com.au/~lucas/2A3AL.jpg
http://webspace.webring.com/people/de/ec1288/images/schematics/quest.gif (think 2A3 instead of 300B)
http://home.earthlink.net/~ivol/moondog_2A3/images/moondog_schematic.jpg
I know there are now values for the Moondog above, but it will give you an idea, mostly the same as the others. This may be of interest:
http://home.earthlink.net/~jeremyepstein/pdf/sp15_2a3.pdf
and this:
http://www.tubecad.com/2006/03/aikido_se_amplifier.png
Cheers
James
http://www.goodsoundclub.com/Site_Images/Sun-Audio_VT-2A3_3.JPG
http://www.jeack.com.au/~lucas/2A3AL.jpg
http://webspace.webring.com/people/de/ec1288/images/schematics/quest.gif (think 2A3 instead of 300B)
http://home.earthlink.net/~ivol/moondog_2A3/images/moondog_schematic.jpg
I know there are now values for the Moondog above, but it will give you an idea, mostly the same as the others. This may be of interest:
http://home.earthlink.net/~jeremyepstein/pdf/sp15_2a3.pdf
and this:
http://www.tubecad.com/2006/03/aikido_se_amplifier.png
Cheers
James
Sun Audio SV-2A3 the schematics from the first link, given by James is my favorite one. I recommend a higher value of anode load. Very successful choice is Hashimoto H-20-3.5U connected to 3.5 KOhm load.
Pocoyo, to make things easy, you can use terminal boards with mounted tube sockets.
From partsconnexion - IAG-68070 and IAG-68067 for mono operation and IAG68071 IAG68068 for stereo.
Similar boards can be found in http://www.tubesandmore.com/
Pocoyo, to make things easy, you can use terminal boards with mounted tube sockets.
From partsconnexion - IAG-68070 and IAG-68067 for mono operation and IAG68071 IAG68068 for stereo.
Similar boards can be found in http://www.tubesandmore.com/
sorry but that from sun audio is not good at all
first, the value of pot 100k is too high for the 6sn7
right value if pot required is 25K...
next the values of Rload at anodes of 6sn7
are too high value.
The load line will be almost horizontal.
and the drop of voltage is probably large,
so the resulting Va will bi lower voltage,
against higher voltage that
should be like Va when we talk about the 6sn7...
next, the device will have more than sufficiant gain,
like common fassion in that design, so the pot most
of the time will be at lower positions causing loss of highs.
*
that is from the first sight cheers
first, the value of pot 100k is too high for the 6sn7
right value if pot required is 25K...
next the values of Rload at anodes of 6sn7
are too high value.
The load line will be almost horizontal.
and the drop of voltage is probably large,
so the resulting Va will bi lower voltage,
against higher voltage that
should be like Va when we talk about the 6sn7...
next, the device will have more than sufficiant gain,
like common fassion in that design, so the pot most
of the time will be at lower positions causing loss of highs.
*
that is from the first sight cheers
Yes, Zoran, the input should be corrected.
First, it is absolutely necessary to add a grid resistor to the first triode of the 6SN7. Otherwise in case of bad contact in the input attenuator the grid of this tube will "hang". The value of grid resistor shold be about 220KOhm. The value of 25 KOhm for the pot is fine. There is no problem with 47KOhm as well.
The input sensitivity is about 250mV for full power. If a lower sensitivity is necessary, an additional input attenuator can be applied. The reserve of gain can be used for NFB as well (for those who admit it in the SE stages).
First, it is absolutely necessary to add a grid resistor to the first triode of the 6SN7. Otherwise in case of bad contact in the input attenuator the grid of this tube will "hang". The value of grid resistor shold be about 220KOhm. The value of 25 KOhm for the pot is fine. There is no problem with 47KOhm as well.
The input sensitivity is about 250mV for full power. If a lower sensitivity is necessary, an additional input attenuator can be applied. The reserve of gain can be used for NFB as well (for those who admit it in the SE stages).
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I would lose the pot all together, just put a resistor to ground and use is as just a stand alone amplifier. I posted these because of the fact that the future owner of the amplifier already has the 6SN7's and 2A3's. However if it where I, the 6SN7 cascade would not be my choice. I would try very hard to find a couple of 6SL7's to serve as input tube. With these I would build up something like the Morrison Micro:
http://www.the-planet.org/images/2A3--6SL7_small.jpg
Much simpler design, losing some capacitors (including a coupling cap), and in general losing one entire triode section. I would then use the 6SN7's to build a simple line amplifier. Search around for Frank's 6SN7 and 6SN7 versions of the Bottlehead Foreplay.
As for wiring, I would use component leads where ever possible. Us terminal strips as suggested above by Rutcho. Otherwise I would 24awg to 20awg (roughly) solid core copper or silver, which ever. Just use the shortest runs needed, high quality passives, and high quality Teflon or cotton insulated wire and you will have a good build. Most of all, use high quality solder with good technique to ensure good solid joint. Make sure too that you use the highest quality output transformer you can afford.
Cheers
James
http://www.the-planet.org/images/2A3--6SL7_small.jpg
Much simpler design, losing some capacitors (including a coupling cap), and in general losing one entire triode section. I would then use the 6SN7's to build a simple line amplifier. Search around for Frank's 6SN7 and 6SN7 versions of the Bottlehead Foreplay.
As for wiring, I would use component leads where ever possible. Us terminal strips as suggested above by Rutcho. Otherwise I would 24awg to 20awg (roughly) solid core copper or silver, which ever. Just use the shortest runs needed, high quality passives, and high quality Teflon or cotton insulated wire and you will have a good build. Most of all, use high quality solder with good technique to ensure good solid joint. Make sure too that you use the highest quality output transformer you can afford.
Cheers
James
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