Konnichiwa,
Literally hunderts of schematics. You need to define what you want.
This would not be my favourite way of doing things, but (for example) a 12AT7 SRPP could be used. Of course, you'd be better off using a 5965/12AV7/12AZ7 replacement for the 12AT7, plus it is easier to find really good quality ones of these at sensible prices....
A well documented 2A3 project that could use the 12AT7 or 12AU7 (even 12AX7) in SRPP is shown here:
http://www.positive-feedback.com/Issue1/kismet.htm
The schematic is this:
The changes for the 12AT7/12AV7 or 12AU7 and even 12AX7 are nominal, simply make sure the pinning is right.
If you add a switch for the Filament connections you could even use Valves more less compatible with the 6922/6DJ8/ECC88/E88CC/E188CC/7308 et al (also ECC85/6AQ8).
Sure, non of the Valves is maximally optimised, but you can experiment a lot with valves. You could also make the SRPP Cathode resistors switchable (or use a stereo pot 1k+1k linear in series with a 330R resistor each to "dial in" the best sounding operating point.
Even better, you can use the Amplifier also with 45's if you like, so it's quite versatile and a good "learning" excercise.
Sayonara
takashi said:
Literally hunderts of schematics. You need to define what you want.
takashi said:
This would not be my favourite way of doing things, but (for example) a 12AT7 SRPP could be used. Of course, you'd be better off using a 5965/12AV7/12AZ7 replacement for the 12AT7, plus it is easier to find really good quality ones of these at sensible prices....
A well documented 2A3 project that could use the 12AT7 or 12AU7 (even 12AX7) in SRPP is shown here:
http://www.positive-feedback.com/Issue1/kismet.htm
The schematic is this:
The changes for the 12AT7/12AV7 or 12AU7 and even 12AX7 are nominal, simply make sure the pinning is right.
If you add a switch for the Filament connections you could even use Valves more less compatible with the 6922/6DJ8/ECC88/E88CC/E188CC/7308 et al (also ECC85/6AQ8).
Sure, non of the Valves is maximally optimised, but you can experiment a lot with valves. You could also make the SRPP Cathode resistors switchable (or use a stereo pot 1k+1k linear in series with a 330R resistor each to "dial in" the best sounding operating point.
Even better, you can use the Amplifier also with 45's if you like, so it's quite versatile and a good "learning" excercise.
Sayonara
Hey,
If u check out the KR 2A3 end de XLR 300B the price is almost the same ! And thats a nice triode so the price herefore isnt 1/3 !
http://www.blackforestaudio.de/KR_Rohren/kr_rohren.html
Greetz, Lukasz
If u check out the KR 2A3 end de XLR 300B the price is almost the same ! And thats a nice triode so the price herefore isnt 1/3 !
http://www.blackforestaudio.de/KR_Rohren/kr_rohren.html
Greetz, Lukasz
Hi,
KR tubes aren't adhering to original standards so it would hardly be a 2A3 or a 300B for that matter.
Good monoplate Russian 2A3s can be had for less than 25 Euro each.
There's little point in having a 2A3 circuit designed around the original spec and than fit a 40W max. dissipation triode.
EDIT: I just noticed that the KR is rated at 18W max. diss., so it's even less of a "bargain".
Besides KR tubes are sooo overpriced and flaky that I can't think of anyone in their right mind forking out that kind of money.
Cheers,
KR tubes aren't adhering to original standards so it would hardly be a 2A3 or a 300B for that matter.
Good monoplate Russian 2A3s can be had for less than 25 Euro each.
There's little point in having a 2A3 circuit designed around the original spec and than fit a 40W max. dissipation triode.
EDIT: I just noticed that the KR is rated at 18W max. diss., so it's even less of a "bargain".
Besides KR tubes are sooo overpriced and flaky that I can't think of anyone in their right mind forking out that kind of money.
Cheers,
Yes IDD you can get it cheaper but I still think that a KR has something more ! I saw her once and I had to have her ;-) if u konw what I mean ! But a nice Sovtek or Svetlana is good to ! I thinkt that he should start with some cheaper triodes to get the feeling and after all u can still change
Greetz, Lukasz
Greetz, Lukasz
Hello Takashi;
1. Go with the SovTek 2A3 - it's tough as nails and it sounds very good. Also, it's cheap ($30USD each). If you're in the US, Triode Electronics carries them and packs them very well (some of the shipping packages I've received have been badly battered so quality packing for delicate components is a MUST).
2. Good schemos for the 2A3/12AX7? Anything using the 6SL7 as an input/driver is probably fine (the gain of the 12AX7 is slightly higher, but it's close enough). Just check to be sure you are not exceeding the plate voltage or max current ratings in the circuit before building it (of course the 6SL7 has 6.3V on the filament compared to 12.6V for the 12**7 series so you'll have to allow for that too). The 5751 has the same gain as a 6SL7, so you might look at that as well.
3. Look at angela.com for schemos on a variety of 2A3 topologies. I built the "2001 edition" of the JE Labs that's at their "how to" section and it sounds fine. Could I have substituted 12AX7's? Probably, but I already have a stock of old Russian 6SL7's on hand, so why bother?
4. The power supply is all important. If you're using Hammond iron, be aware that the 3xx series of PS trafos is considerably better built than the 2xx series. Also, don't skimp on the OPT's. The cheapest I'd go is the Hammond 125ESE, and the Hammond 1627SE is a very nice sounding bit of iron indeed. Recently I read of problems with the 1628SE, but the 2k5 ohm 1627SE does not seem to have these "issues". I have a pair of them on my 2A3 and am mightily pleased with the sound.
5. For speakers, so long as the crossover is simple (or you're using a single driver like one of the superb Fostex drivers) and the SPL rating is about 89+dB it should be okay for moderate listening levels. I can drive my old EPI100's (8" 2 way using a single cap on the tweet for a xover with 89dB SPL) to satisfying levels in a 10' x 11' room using my DIY 2A3. With my 96dB SPL DIY Fostex's, I can easily fill a larger room with sound or push my little listening room to hearing damaging levels. Don't panic over the low power of a 2A3 - so long as your speakers are moderate to high efficiency and do not have a power draining crossover, you'll be okay IME.
Good luck and all the best!
Morse
1. Go with the SovTek 2A3 - it's tough as nails and it sounds very good. Also, it's cheap ($30USD each). If you're in the US, Triode Electronics carries them and packs them very well (some of the shipping packages I've received have been badly battered so quality packing for delicate components is a MUST).
2. Good schemos for the 2A3/12AX7? Anything using the 6SL7 as an input/driver is probably fine (the gain of the 12AX7 is slightly higher, but it's close enough). Just check to be sure you are not exceeding the plate voltage or max current ratings in the circuit before building it (of course the 6SL7 has 6.3V on the filament compared to 12.6V for the 12**7 series so you'll have to allow for that too). The 5751 has the same gain as a 6SL7, so you might look at that as well.
3. Look at angela.com for schemos on a variety of 2A3 topologies. I built the "2001 edition" of the JE Labs that's at their "how to" section and it sounds fine. Could I have substituted 12AX7's? Probably, but I already have a stock of old Russian 6SL7's on hand, so why bother?
4. The power supply is all important. If you're using Hammond iron, be aware that the 3xx series of PS trafos is considerably better built than the 2xx series. Also, don't skimp on the OPT's. The cheapest I'd go is the Hammond 125ESE, and the Hammond 1627SE is a very nice sounding bit of iron indeed. Recently I read of problems with the 1628SE, but the 2k5 ohm 1627SE does not seem to have these "issues". I have a pair of them on my 2A3 and am mightily pleased with the sound.
5. For speakers, so long as the crossover is simple (or you're using a single driver like one of the superb Fostex drivers) and the SPL rating is about 89+dB it should be okay for moderate listening levels. I can drive my old EPI100's (8" 2 way using a single cap on the tweet for a xover with 89dB SPL) to satisfying levels in a 10' x 11' room using my DIY 2A3. With my 96dB SPL DIY Fostex's, I can easily fill a larger room with sound or push my little listening room to hearing damaging levels. Don't panic over the low power of a 2A3 - so long as your speakers are moderate to high efficiency and do not have a power draining crossover, you'll be okay IME.
Good luck and all the best!
Morse
hi,
here's another...
http://www.jeack.com.au/~lucas/2A3SRPP.jpg
Frank out of these 2 links and also bearing in mind this amp also
http://www.electra-print.com/2A3DRD.html
which one would you build if you were to build a se 2a3 amp???
Thanks
Raja
here's another...
http://www.jeack.com.au/~lucas/2A3SRPP.jpg
Frank out of these 2 links and also bearing in mind this amp also
http://www.electra-print.com/2A3DRD.html
which one would you build if you were to build a se 2a3 amp???
Thanks
Raja
I've built an SE 2A3 with a 6SL7 SRPP driver stage (which had a pretty low bias current, I'll admit, but I was following someone else's design). Based on advice I got on this forum, I changed my driver stage to a CCS loaded ECC99. The improvement was pretty dramatic. This is the amp that is currently driving my midranges and tweeters.
I also second the recommendation for the SovTek 2A3s. They sound pretty good, and you can run them a little hotter than you can with NOS tubes and gain a litle more power and (I think) a slightly more open and driving sound.
I also second the recommendation for the SovTek 2A3s. They sound pretty good, and you can run them a little hotter than you can with NOS tubes and gain a litle more power and (I think) a slightly more open and driving sound.
Sorry, I don't. I tried to describe it here:
http://www.diyaudio.com/forums/showthread.php?postid=351999#post351999
http://www.diyaudio.com/forums/showthread.php?postid=351999#post351999
Do you mean the complete schematic or just the CCS?
Like Saurav you can just buy ( or build... not sure if the schematic is OUT THERE) the C4S from bottlehead.com or get
Kevin Carters' from K&K Audio http://hometown.aol.com/kevinc927/index.html
Or you can build mine. (Well my schematic that is ... Gary Pimm and Sector7G essentially designed it.)
See the rest of my page for determining R?
http://home.zonnet.nl/horneman/mosfet.htm
The CCS fits in the place where your plate resistor would normally be.
Like Saurav you can just buy ( or build... not sure if the schematic is OUT THERE) the C4S from bottlehead.com or get
Kevin Carters' from K&K Audio http://hometown.aol.com/kevinc927/index.html
Or you can build mine. (Well my schematic that is ... Gary Pimm and Sector7G essentially designed it.)
See the rest of my page for determining R?
http://home.zonnet.nl/horneman/mosfet.htm
The CCS fits in the place where your plate resistor would normally be.
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