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RE: Perhaps Joe could offer a comment, but here’s what I have found...

Posted by petercapo (A) on March 24, 2014 at 08:20:37

In Reply to: RE: Perhaps Joe could offer a comment, but here’s what I have found... posted by Joe Curcio on March 24, 2014 at 07:51:54:

Thanks for your response, Joe. I am fairly stumped as to the breakup I heard. I am working on a second rebuild with a few changes but nothing I am terribly confident would make a difference.

There was one thing, though. It uses a cap board that emulates the original power supply topology but with low ESR electrolytics. I jacked-up the capacitance quite a bit. I think, but am not sure, that the problem might have gotten a bit better when I added a bleeder resistor. Besides bleeding the electrolytics when the preamp is shut off, I understand that a bleeder resistor could also offer a form of regulation during operation, is this correct?

Could it be possible that the breakup had something to do with the power supply? The "breakup" I heard when the volume increased reminded me of the sound of power supply capacitors draining when power is turned off. Again, same circuit as the original, but capacitance was increased to over 500uF for the B+ and something like 24,000uF for the filament supply...

I understand that some feel large increases in capacitance will not yield much benefit, but I am wondering if it can become so much that it could actually cause a problem like what I was hearing?

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