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To switch quad cap or not..

Posted on July 18, 2016 at 09:29:04
Posts: 8
Joined: February 17, 2008
I have 2 Mk3s that are dated 1959 and 1960 according to bias pots. Both are working well. Zero hum. Do I replace the Quad Cans or leave em.. I remember doing this once on my ST70 and it actually hummed more and I put the original can back. It was an Aero cap. Are the new replacements as good quality as the origial cans? I just hate to fix what ain't broken. I am a tech so I know damn well caps get old and the possible issues it brings. Do they replenish with a lot of use or reform? Curious to hear your thoughts on the issue. Also what current replacement brands are the best. NO Cap salesman please.. lol.


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RE: To switch quad cap or not.., posted on July 20, 2016 at 11:27:33

Posts: 184
Location: SOCAL
Joined: October 28, 2008
If you were to replace them check out Dynakitparts, they have one that's rated at 550VDC, 600VDC surge, could be good if your AC line is on the high side.



The German made quad cap rated at 550V is good but spendy......, posted on July 25, 2016 at 18:32:03

Posts: 3931
Location: Portland, Oregon
Joined: May 26, 2005
February 1, 2012
.....I'm building another pair as well and have decided to go with the cap boards that mount under the chassis from Sheldon Stokes at SDS Labs. You leave the old quad cap in for looks, but mount modern, low ESR, caps that are bypassed with film caps, under the deck.

The original was underrated at the lower mains voltages of a bygone time. At todays line voltages it is an accident waiting to happen.


RE: To switch quad cap or not.., posted on August 7, 2016 at 14:56:36

Posts: 2947
Joined: August 16, 2004
That's the key in this whole thing. If it isn't broken then don't fix it. If it plays well and there are no hum issues then why do something that might not be better. Most of the modification boards and the such sold is a way to earn is living in this hobby. Not so much does it make it better.

Just my take on it!


RE: To switch quad cap or not.., posted on August 7, 2016 at 15:00:20

Posts: 2947
Joined: August 16, 2004
But yes! Changing and old part will give you much more years of reliability but maybe don't expect sonic miracles. If you get sonic benefits then that's always a plus. Always try to put back as close to original values as possible. These designers knew what they were doing when these circuits were designed.

Again! Just me venting!


RE: To switch quad cap or not.., posted on August 8, 2016 at 14:41:44

Posts: 53
Location: Long Island,NY
Joined: May 22, 2015
Omnibuss, I agree with Viridian about going to the SDS boards. I did the same on my PAS-3x.
The advantage being modern, easily replaced caps. The CE Manuf. caps are still iffy in my book. The first one I used leaked inside my preamp and damaged the plating. Another one had a section open up thus rendering my ST-70 a 12w/ch amp instead of 35w/ch. I tacked another cap across the bad one and it came right back up.
When I questioned CE about it, they said they hadn't heard any complaints (in 2007).


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