Thinking of constructing a 2A3 based amp.
Design aims would be:
1) Single ended topology
2) Simplicity - minimum number of components / stages with the best achievable sound quality.
3) No feedback if possible. If feedback needed, limited to local feedback.
4) Low cost - no exotic tubes or transformers.
Any suggestions by the great tube gurus out here?
Design aims would be:
1) Single ended topology
2) Simplicity - minimum number of components / stages with the best achievable sound quality.
3) No feedback if possible. If feedback needed, limited to local feedback.
4) Low cost - no exotic tubes or transformers.
Any suggestions by the great tube gurus out here?
There must be literally hundreds of schema out there (I've yet to hear a 2A3 SE or P/P that I didn't like), but it would hard to go wrong with
Angela Electronics:
Simple SE 45/2A3 Amp for First Time DIYers
Bottlehead Stereomour:
Stereomour Stereo Single Ended 2A3/45 Integrated Amplifier Kit
Electraprint's DRD:
Electra-Print.com 2A3 DRD Amplifier
(of course Jack would be happy to supply the iron)
for those with more adventurous spirit and deeper pockets:
MagneQuest DIY: Jean-Francois Lessard's 2A3 SETH SA-240 Push-Pull Monoblock
and by non-exotic, it's assumed you mean current/recent production entry level priced ( i.e. Sovtek /EH/ Valve Art etc.) as opposed to either NOS RCA/Cunningham or Shuguang Treasure series
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EL84 😕
http://www.tubemaster.de/e-diy-EL842A3.html
looking up EL84 drive 2A3, this Aikido drive 2A3 popped up
http://singlevalve.web.fc2.com/Aikido2A3/Aikido2A3.htm
Thanx tinitus. Currently am running aikido as my line-stage, so it would definitely make sense to use another aikido 🙂
EL84 is also another fave tube of mine (and I have several extras lying around), so definitely another possibility.
Hi!
You might want to have a look at the single ended amplifier concept posts on my blog. The schematics I published are with 6CB5A output tube, but it can be replaced with a 2A3 with the same driver stage. In fact I have built it with 45/2A3 already. I'd recommend the Lundahl 1663 as output transformer.
In upcoming posts I will show how to convert this concept to DHT output tubes
Best regards ... Thomas
You might want to have a look at the single ended amplifier concept posts on my blog. The schematics I published are with 6CB5A output tube, but it can be replaced with a 2A3 with the same driver stage. In fact I have built it with 45/2A3 already. I'd recommend the Lundahl 1663 as output transformer.
In upcoming posts I will show how to convert this concept to DHT output tubes
Best regards ... Thomas
My version of SE 2A3 is:
- 9 - 10 passive elements per channel.
- two stage ampl.
- No FB.
- pretube E180F Phillips, or 6E5P /Russian tube/
- output transf Hammond 125FSE /70$/, guarantied 20 20000 Hz. I measured with scope and signal generator /don't see that brand wrote 150-15000, ha-ha. This trani 90 ma, 10 sq. cm is for 300B, 2A3. 6L6, EL34, it was first brand's recomendations 4 years ago....Now they recommend for 2A3 trany for 200 and more $....ha, brands trick!!!!./
- 2A3 RCA /90$ each.
- chase Hammond Alu.
I can post my schematic.
This ampl. kicked 2 Mosfet Hitachi with "brushes".
https://picasaweb.google.com/azazello52/Amplifiers#5556534527250384578
- 9 - 10 passive elements per channel.
- two stage ampl.
- No FB.
- pretube E180F Phillips, or 6E5P /Russian tube/
- output transf Hammond 125FSE /70$/, guarantied 20 20000 Hz. I measured with scope and signal generator /don't see that brand wrote 150-15000, ha-ha. This trani 90 ma, 10 sq. cm is for 300B, 2A3. 6L6, EL34, it was first brand's recomendations 4 years ago....Now they recommend for 2A3 trany for 200 and more $....ha, brands trick!!!!./
- 2A3 RCA /90$ each.
- chase Hammond Alu.
I can post my schematic.
This ampl. kicked 2 Mosfet Hitachi with "brushes".
https://picasaweb.google.com/azazello52/Amplifiers#5556534527250384578
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Interesting concept. 🙂
How does the 6N7 perform? I always thought it was a designed as a class B amplifier. In your circuit, is it running in class A?
Another interesting approach, with low parts count. As it happens, I also have a pair of 6E6P. Can I have a look at the schema? 😀
Hi!
The 6N7 was designed to be used either as Class B output stage or as Class A driver with both halves in parallel. It performs very well and is cheap.
Thomas
The 6N7 was designed to be used either as Class B output stage or as Class A driver with both halves in parallel. It performs very well and is cheap.
Thomas
6N7 is an interesting high - mu triode with nice right-handed linearity, but works well like a small signal triode in left-handed mode. I plan to build one amp using it.
https://picasaweb.google.com/azazello52/KVM#5413313827582447474
Plate resistor 33 kohm now is 13 kohm!
Poti 100 ohm now isn't in heating!
Hmmmm is abs. zero with AC heating.
Yours 6E6P are very suitable for prestages. Very close tubes are 6P15P and 6P9 /Russians/.
https://picasaweb.google.com/azazello52/KVM#5574719812792812978
There is a schematic SE 300B & 6E5P, You can use the same prestage /with Yours 6E6P/ for 2A3.
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Here's one that meets the criteria. SE, two gain stages, no FB, low part count, and nothing exotic. I can vouch for it. I've built an 801 amp, based on the same idea. http://www.diyaudio.com/forums/tubes-valves/125488-loftin-white-801-amp.html#post1551490 Power supply is simple LCLC or CLC supply. All capacitors can be film caps, as no large caps are required. It sounds very nice and is as quiet as a grave (I often use it as a headphone amp).
I didn't use the bootstrapped follower, as I didn't need a higher gain input tube. But I will try it at some point. You don't have to use the same tube for the input and follower, but it will work well that way. Darius (former member oldeurope, who developed the amp, has a 300B version). With a 2A3 you can probably do fine with AC heating on the filament, if you don't want the complexity of a DC heater supply.
Sheldon
BTW: Even if you don't build it, it's worth studying. Those guys (L-W) were clever and subtle.
One last thought: Once set up, the operating points are self settling. It requires no adjustment, and stays stable for the life of the tubes.
I didn't use the bootstrapped follower, as I didn't need a higher gain input tube. But I will try it at some point. You don't have to use the same tube for the input and follower, but it will work well that way. Darius (former member oldeurope, who developed the amp, has a 300B version). With a 2A3 you can probably do fine with AC heating on the filament, if you don't want the complexity of a DC heater supply.
Sheldon
BTW: Even if you don't build it, it's worth studying. Those guys (L-W) were clever and subtle.
One last thought: Once set up, the operating points are self settling. It requires no adjustment, and stays stable for the life of the tubes.
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