Lin topology current driver rebuild

[Shredly]

Originally posted by AndrewT
Hi,
it difficult for me to be objective in this situation since you have the equipment in front of you.

I concur. And it's very difficult for me to be objective even with it in front of me, because how much hum is irritating is pretty subjective too.

Originally posted by AndrewT
So, as a result, I still think that the description of the hum was much more likely to be caused by a grounding error.

The only thing the least bit hinky was that connection to the steel chassis through one of the standoffs; the rest was pretty conventional, according well with your description of the right way to do things.

Originally posted by AndrewT
I am surprised that the ripple in the PSU was causing this, but you have a solution.

I wonder if all those extra resistors off the rails reduced the PSRR?

It is entirely possible. But adding ripple suppression is far easier than modifying the Lin amp board, and far less likely to result in reliability problems; uncomfortable visions of piggy-backed resistors and capacitors, and jumper wires and cut traces, fill my head, accompanied by dancing sparks and the imagined smell of burning insulation. :P

Originally posted by AndrewT
Keep us informed of how the multiplier performs with some details/schematic of the final solution.

Well done, regarding persistance and debugging.

You got it, and thank you. I enjoy playing around with this stuff, luckily, though my patience is growing thin; I have an offer to get together with some folks and make some music, and I'm going to need a workable permanent solution pretty shortly.

[Shredly]

See the power supply thread for the schematic, or complain a little bit and I'll post a link to the power supply thread. I'm too lazy right now; I worked for about 8 hours getting it nice and properly wired (I used #12 copper for the ground, and #16 copper for the rails, and solid #22 hookup wire for the control signals).

There were no remaining glitches under load test, and in the amp it's golden. I'm not sure what kind of sound problems people had; to me it sounds like a million bucks, though admittedly I only hammered it once to check it wouldn't drop out. I'll really beat heck out of it tomorrow, though. 8D

I'll let you know if I see any problems, but given how I tested it, I can't see any that look likely to crop up.

And it's quiet as the grave- even the reverb is quieter than it was, you can just pick up the slight hum over the sound of the fan (and I mean sound, not interference- I checked with my head right in front of the speakers). I'm gonna get some double-takes the next time I trundle this thing out there.

Thanks a million Andrew, not least for putting up with me.