Hello all,
I've been slowly purchasing components for a 2A3 single ended stereo amp. I probably should have picked a schematic first, but what the hell.
I've got a matched pair of 2A3 Electro Harmonix Gold Grid triodes, a couple old stock 6sn7gt(b) and four 76 triode tubes. I don't know if they are at all good. I don't have a tube tester. I should be able to pick up tested NOS 76's for $20 a pop, I hope. They make new 6sn7, so I'm less concerned about that.
I've purchased an Edcor XPWR067-100/120. Specs as follows: 320v-0-320v @150 mA; 6.3v @3A; 5v @ 3A; and two 2.5v @ 3A
For output, I have two Edcor GXSE10-8-5. Specs: 40hz-18khz, 5k, 8 ohm, 10 watt. I also have two 15 watt Classic Tone model 40-18031 that have 5k and 8k primaries and 4-8-16 secondaries that I have considered for this project. The core on the '15 watt' guitar amp OT is smaller than the '10 watt' hifi amp OT. Which I understand, but...something to consider. I have the suspicion I will end up buying larger OTs as an upgrade in the future while using the Edcors for now.
For rectification, I have a bunch of old stuff: 80, 83, 5U4GB, 5V4G, 5Y3G, 5Y3GT, 5Z3. I'd like to stick with a larger sized tube for aesthetics. Maybe the 5V4G for the ST shape.
Some of you already guessed which schematic I've had my eye on so I'll share with the rest of you:
Attachment:
JELsc-ST2A3DX.jpg
I do have a concern though. My output transformers both have 5k primaries and schematic shows 2k5 or 3k5. Any suggestions on this front? The 15w guitar amp OTs have 4-8-16ohm on the secondary side so I could get the 2.5k with the use of 16 ohm secondary and 8 ohm speakers, right? I think I'd rather run the 2a3's at 5k, use the Edcors and adjust the cathode resistor.
Another concern is the direct coupling between the 76 and 6sn7. Should I be concerned? I would not like it if a 76 failed and took out a good 6sn7 or vise versa. This is one of the reasons I was turned off by the Loftin-White schematic; direct coupling and the risk of killing relatively expensive tubes, the 2A3-EHs (or so the internet stories say!?!?

)
I have another Edcor power transformer slated for a 'yet to be designed' preamp. XPWR-136-120 Specs: 250v-0-250v @60mA and 3.15v-0-3.15v @2A. Would I need a preamp to drive the above schematic? I'm expecting: no. I would like a volume pot somewhere, though. Where should I put one? After the 6sn7 or after the 76? What would I change to get that in there?
Any comments? Any schematics you think I should consider? I would prefer not to use any miniature tubes to keep the big tube vibe going.