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Re: Single 45 Amp question and pics

Posted by mwiebe on March 1, 2007 at 04:32:28:
Nice looking amp, great job on putting it all together.
Those voltages are fine, though looking at the schematic I would expect it to be a bit higher if you built exactly to that schematic. Have you checked the plate current through each tube? I expect your 6SN7 should be 10ma or less, and the 45 should be around 35ma. If you are in the ball park then you are okay. You may want to look up data sheets for both tubes to see where you are in the plate curves.
At that B+ voltage and cathode resistor you can drop a 2A3 in, but always come up slowly with a variac if you are not comfortable and keep an eye on plate voltage and current. Since the filament requirement is different and the 2A3 pulls more juice you need to think about whether the winding or transformer you are using has the current headroom. “Optimize”? Well that’s were the fun is. Since the 2A3 plate resistance is lower the 45 a lower impedance output transformer could be used. But tweaking a driver circuit to your ear and speakers is what this is all about. I don’t think optimize translates between people, but experiment and listening does. And there are plenty of alternative driver schematics on the net for ideas.
Matt