Ripple current Q for amp capacitors

Thanks.. I guess that's why they are twice as much. No other brand is close, if it even exists (-10/+75%). I was reading about reforming the large caps. I'm still not entirely clear on a rig to try it, and i've been rebuilding crt monitors and late 70's-early 80's arcade machines as a hobby for 3 decades. But a question I had, and maybe you'd know, is how is applying a low voltage for a while to reform a cap, different than just leaving it plugged in for a long time, then unplugging it and letting it draw down? Shouldn't they naturally reformat themselves during regular use? 

So it seemed to have a slight hum for a while. I moved out of a long term house, then rented for about 6 years and had the amp sitting in a box. When I built the theater, I bought the second PM1000. I have 11 channels in there (A Parasound Halo rounding it out). Everything is fed through a Tice Signature III power conditioner. I noticed the hum fairly soon I recall, but the build took a year so wasn't in the mood to hit something else and take things apart. But it got to the point I noticed it every time I went in the room.. and this is a treated space. But I think it might have seemed like more based on where I stood. If I put my ear against the wall where a speaker was, I could definitely hear it, and determined which amp it was.

As mentioned, i've rebuilt lots and lots of crt's and arcade pcb's as a hobby, and it is amazing what new caps will do to a crt. But I know those run far hotter. Still, I have always wondered if the same degredation happened in amps. The caps I took out, were as good of a reading as new ones were which completely surprised me. Did the hum go down? I would say it probably cut it in half.. but sadly the years of Orion amps and subs in my car in the 80's took a toll on my hearing so have a permanent slight ringing, so I can only judge by what range I can still hear. I can't stand in an open space and hear it easily like before.. I have to think about it and really try.. but if I go to a speaker I can definitely hear it. I used to have solid silver interconnects, but those started to get flaky at the connector, and I didn't want to have them in the system and not notice a channel  was out (like had happened before). I also thought the wires might be contributing to the hum, but I replaced 'everything' with Mogami wire to eliminate other sources before opening the amp.

The second PM1000 seems to be fine.. but it may have been taken out of a working environment right away and didn't have the 6-7 years of downtime my first one did. It's this downtime that has gotten me curious about reforming the caps. If I could get new date code ones I would just replace.

Thanks for all the help so far.. When I went this route I reached out to Noble Electronics who are the only authorized EAD service center to ask if there were any other possibilities or weak spots, and he only suggested the two large caps. I guess i'll focus on those, and maybe reach out and see if he'd suggest an alternative or what he uses.

It’s half the price of the CD 100k cap so that would be great. Size seems to be about the same as whats in there. No I have never measured the voltage, only had it open for the first time recently. Noble does transformer upgrades and things for EAD parts, and didn’t mention going up. I believe he helped design these. What is the difference, of the original cap being -10/+75%, compared to the TDK cap that is a flat 20%? Can the CD store basically 175,000uf if needed? That seems to be the only parameter that is making this replacement really difficult.

Thanks a ’lot’ for all the help here.. I should have started this thread months ago. Everything I have done in the past has been max 1000uf, or the occasional 3300uf in the audio amps of old arcade games, and topping out at 470 everywhere else. I’ve always just bought 105’s and paid little attention to anything else as the machines after restoration would never be routed, or left on more than the occasional hour here and there and they weren’t exactly made for SQ. But with this amp, it literally changed a part of my life going from what I thought was ’high end’ at the time, a Yamaha rx-v992, to a Lexicon MC-1 and this amp. That first time turning it on and hearing that combo is something I’ve never forgotten so I’ve been incredibly paranoid of not getting the right part in there.

Question on that above though as that’s interesting.. I assume at the time EAD had capacitance testers, and that every cap in this size they got, would be tested first to see where it was at. Why would they pick one like this with potentially a large throw away range? Or did they pick it because on the low capacitance end they would by odds be closer to 100k which was important to not be below that, but on the top end of the error they didn’t care if it was 120 or 150? I’m sure package size would have played a part as well.. there are two of these in each amp.

All the other caps, I think were 100 and 470 on each side of each channel throughout and were mainly Panasonic. I say mainly because there was one, that was a different brand I can't recall right now that had initials written on top. I saved it just in case, but it wasn't special, just a different brand and metered about as well as all the others. Not sure why it was initialed unless it was just to signify who assembled or something.

So when I have read before that a lower ripple is better for SQ because it filters more, if that’s not really true, and that the esr and ripple ratings are ’only’ an indication of how well it will take abuse, and by that it’s lifespan, and that every 100k filter cap will pretty much ’sound’ the same? If people are picking these specific brands like Black Gate, Audio Note, I have to think there is something that makes a difference. Which spec is it? Or is it more what materials are in it.