2A3 Single Ended Parallel

Here is a schematic of an amp you don't see too often... a single-ended parallel 2A3. I bought this many years ago during a business trip to Hong Kong. It sat for a long time after I bought it. I didn't even connect it to anything probably for at least a year after I bought it. Long story short, it was horrible from the factory. It had a lot of hiss (noise), distortion was high and it had some ground issues. This particular model has now been discontinued, but there is some info floating around on the web that this is a push-pull design. It is not, it is single-ended parallel.

After some tinkering and general clean-up, this amp is now one of my favorites. It is very quiet for having AC on the filaments. Distortion is much lower now as well. The iron in it appears to be suprisingly good. High-end is out to 45kHz. The bottom end is good too.

The SRPP 5751 replaced a 6N2 tube. I can't remember the original input tube configuration, but I have it saved somewhere. The 5751 doesn't seem to have any problem driving two 2A3's. Gain is a bit more than I normally like, but since it is super quiet and the distortion is low, I can live with it the way it is.

The Chinese factory 2A3 tubes are well broken in and that does make a huge difference. I'd say these 2A3 tubes have 300 hours on them. The JJ5751's only have maybe 40 or 50 hours on them.
 
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paul_b

Active Member
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That would be really strange. It would be a paralleled 2A3 amp that makes about the same power as an amp with one 2A3 per channel.
 
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