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Utilizing resources available on this website, I was able to tweak my project toward a very satisfying conclusion. The 6n14n’s are singing very nicely. However….

I did use 12ay7’s in V1 and V2. They are still in there. This seems to give me a bit more latitude with gain and MV.

Sacrilege? Bad idea? I’m open to suggestions and your thoughts on this.

It’s great to be here.

Does it sound good? Do you like playing through it? Those are the most important questions, besides:

Are your voltages in a good place for those tubes? Test your voltages and check the tube datasheets, and see where you are.

I’ve got a Mouser order on the way. My goal is to get the first B+ node down to 330 from 352. The zeners I ordered, should get this done. I’ll record voltages afterward.

I’m also scraping together components for a passive snubber network for the output tubes.

And I found in my stash a Regency labeled (Sylvania) long plate 12ax7. That’s now in the V2 position. Very pleased.

Dropped in a 180ohm cathode resistor to soften the plate current in the output tubes. I’ll fine tune it once I get the B+ to target.

She’s playing very nicely now. I don’t “need” a snubber network, but when I drive it, I think I might. Odd noises. Like a harmonic hissing sound. Crank it back and it’s pretty clean.

If you're using typical 18W transformers, you want to be at least 340VDC for your B+. Normal target is 345VDC +/- 5V.

330 might get you into the muddier sound range. Depends on your iron, but that's common. The lower you bring your B+, the lower your headroom will be. 352 is really not bad. I wouldn't drop more than 10V.

Thanks! Useful information. Ok, 340-345 it will be.

I’ll then record all voltages and target 12 at the output tube cathodes.

Full report in a few days. Thanks again.

JohnJankowski wrote: ↑

Mon 05/08/23 11:36 pm

Thanks! Useful information. Ok, 340-345 it will be.

I’ll then record all voltages and target 12 at the output tube cathodes.

Full report in a few days. Thanks again.

12V cathode voltage is a good average, but what you're really targeting is 85% power tube dissipation. You can calculate that here when you have your voltages: https://robrobinette.com/Tube_Bias_Calculator.htm