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I think I sent him a message, but which cap?

Nice! I think I've found it - Dual-to-Quad Op Amp Adapter – BrownDog 070401 But the original question still remains. 3 seconds I'm sure meets most needs, but I assume there is a simple RC network that sets the timing.

Going to be a challenge as the pin outs don't match. May be able to fab an adapter of some sorts. OPA4134 would be the choice.

Thanks for the recommendation. Indeed, the single supply causes problems. And for the PL4000, each and every board seems to have input and output coupling capacitors. I'd be bothered less if there was one in the beginning and one in the end, but it seems each board has another level shift...

Pretty sure. I've attached a copy of the schematic of the Logic board - PL04. This PL4000 has the later version of the board which uses a quad op amp and has a timing circuit made up of Q5, Q6, R25, & C10. Both channels exhibit exactly the same behavior. B+1 is the 30vdc direct from the...

So I sent this directly to Don, but decided to make it a thread instead. I want to adjust the timing of the DCP. Currently the relay energizes in about 3 seconds (as designed). My PL4000 preamp does not output a signal for about 15 seconds, and then when it does, goes through a short 1-2 second...

I want to adjust the timing of the DCP. Currently the relay energizes in about 3 seconds. My PL4000 preamp does not output a signal for about 15 seconds, and then when it does, goes through a short 1-2 second transient where it outputs a 0.7 vdc signal. This is enough to trigger the DCP (and...

My reading of the specs looks like they are good to 250vac, so you're okay. Not your standard electrolytic. If I'm lucky, I learn something new everyday.

The original cap you showed, which was orange, was an NP - non polarized - cap. Those big black ones are polarized (I think, since they are rated for 400 vdc and have a + sign at one end. Are you sure they will be ok in a crossover network?

Nice! Could you make a simple sketch of your ac wiring and where it's shielded? Might be helpful to those who want to reproduce your results. Picture is worth a thousand...

Shouldn't that be 104.6dB? db = 20log10(v1/v2) = 20 * log10 (60/0.00035) = 104.6dB

Agree, otherwise all that coax cable we use to route low-level audio signals was for naught. Faraday cages do a pretty good job shielding from RF. Peter, are you now satisfied with the end result, i.e., can you live with the current level of noise reduction? Or is there still a burr under...

Chekov getting an earbud.

How long before they turn into those bugs in the Star Trek movie? That is, at what point can you not stand them in your ears?

Super! Glad it worked! It's the end result that counts.

Tools. You need the tools. And the shop. Would probably help if you aren't married. Or have a wife who digs restoration.

The chassis should work fine assuming it's connect to DC ground and may work even if it's not since there is significant capacitance to earth ground. Otherwise the ground between the power supply caps. Either will provide a low impedance return to AC.

You can lead a horse to water... Peter, one last try and then I'll keep my mouth shut. First, what's so stressing about desoldering? Piece of cake if you have some solder wick and perhaps a solder sucker. About a 15 minute job and most of that is waiting for the iron to heat up. Twisted...

Peter, in addition to raising the board, you should seriously consider the shielded twisted pair for the AC line, IMHO. This one change alone may give the biggest bang for the buck and it's much simpler than trying to shoehorn in a shield.

Sounds like the B+ & B- are okay. On mine, I accidentally shorted the -15vdc test point to the nearby heat sink. This took out the -15v supply and blew one of the pico fuses on the right board. This caused the left output to go B+ (or nearly so), so I suspect the cause of his left output...