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In Reply to: RE: ARC PSU caps choice posted by Wojciech on August 15, 2016 at 14:50:23
I agree with Eli. I'll add that you can get the data sheets for most caps. Here are the things I look for in electrolytics:
Rated lifetime and temperature are related; cap life is cut in half with every 10 degrees C temperature increase. So a cap rated 5000 hours at 105C is equivalent to one rated 20000 hours at 85C. Remember that the cap temp depends on the air temp, the radiation temp of nearby components (resistors and heat sinks, mostly), and the ripple current. The first cap in the PSU has usually by far the greatest ripple current, so that one is the most important for those ratings. PSUD will give a good estimate of the rms ripple current.
For sonics, I look for caps with good high frequency performance. Usually this means there are acceptable ratings at 100kHz, not just at 120Hz. Fortunately, the advent of modern switching power supplies has forced cap makers to provide such ratings for many of their products. The last cap in a power supply carries the most signal current, so that high-frequency rating is most important there.
There are certainly other effects that can only be evaluated by listening, but the above will narrow the field considerably.
Follow Ups:
sigh :) I knew it's not going to be simple. I warned that guys , my so called friends that Audio Research behemoths are not for the people with thin wallets. I told them I'm not going to spend hrs repairing their junk just because they heard the name Audio Research and aspire to have well recognized, expensive brand in their collections, and I told them that I don't know how to make them to sound more like Audio Note or Jadis amps :)do you ?? Do you know what brand Audio Research uses to service those amps now? I think it will be good enough . Thank you Paul and Eli for helpful posts . I will keep them for the purpose of my own builds and modifications .
The original capacitors are in all likeliness CDE (Cornell Dubilier). Pretty run of the mill caps. If you're doing just the mains, these will be fine. If you're doing some of the smaller ones and filament caps, I would go with Panasonic, or Nichicon as mentioned. Any axial caps use Vishay/BC or F&T.
Dan Santoni
There is a good chance the lytics in the amp are still good.What I would do you is get some 30uf to 50uf film caps and put them in across each of the lytics and I guarantee you that will be a noticeable change he will love..This will mean that the film caps are doing 80% to 90% of the work at any given time and it will dip into the lytics at higher transients.If you have any bad lytics in there you have to change them but the film caps are going to give you the most noticeable change.They are small enough now to mount off to the side and fit in a nice neat stack.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Edits: 08/15/16
I would agree that installing some film bypass caps may yield a much better sonic impact than just changing the old lytics for some new ones. only problem is space. Since ARC has everything on a circuit board, you will have your work cut out to remove or even add parts to the circuit. The last time i worked on an ARC 60? (the one with pp 6550) there was a lot cussing going on. cheers, Dak
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