2000s Recap / Capacitor Info

[n2000s]

Recently bought a 1970 2000s with the tube rectifiers and will be soon replacing the power cord and recapping it. I have read many posts here and I know there is some differences of opinions on recapping but with this one I'd like to keep it very close to stock and would love some help on narrowing down the best quality parts and suppliers.

A few photos of it now with original caps.





Parts considered so far.

30/20/20/20 uF @ 550/600 VDC
Product Detail: Multi-section Electrolytic Capacitor

Sprague Atom electrolytic capacitor, rated 20µF / 600V, 85°C
Atom Electrolytic Capacitor 20µF / 600V
(My 350B has two of these and this 2000s has only one) Does this have to do with it having the tube rectifiers?

Electrolytic Capacitor, 50uF, 150VDC
Some here:
https://taweber.powweb.com/store/capord.htm
VISHAY SPRAGUE|TVA1414-E3|CAPACITOR ALUM ELECT 50UF, 150V | Newark.com 8 UCC 34D597 50uF 150V 85C Elect. Capacitor - eBay (item 200589837724 end time Apr-21-11 12:47:48 PDT)
I also read a member used 47uf@250V caps to replace the 50uf@150V. *Different specs but would this be ideal?

Anything I should go ahead and do while it's a the tech?
In the end I want to stick close to the original sound and cap values but using the highest quality components.
Any help from the forum would be great!

[jmaf]

My 2 cents: when buying ebay electrolytic caps, or caps from unknown stores, antiques especially, do ask about the age of the cap.

NOS electrolytics are a trap. I've bought some spragues from ebay only to find out they were likely made in 1990, due to their physical appearance. Old electrolytics are not valuable, they have no vintage value at all, they're only old failure-prone caps.

[soundmasterg]

You should read up in the threads on the forum about using series connected caps in the first two stages to get an adequate voltage rating for today's line voltages. Most vintage Sunns are over the cap rating if used with a can cap rated at 525v, and while they will work for awhile, they will fail sooner while being overloaded like that. There is also the SDS cap board which should work fine in there. Sprague Atoms are greatly overpriced for what they are. I have some 20uf 600v Atoms from the mid 90's that I've kept charged over the years but will probably end up throwing out as there isn't much call (or room in an amp) for such a huge cap. The cap for the bias that you mentioned would work just fine.

I'd recommend some series connected caps with parallel resistors for the first two stages, staying close to stock values if you want close to stock sound. For bass, I prefer larger caps as it makes the bass quicker and tighter, and reduces hum and noise over vintage. The 30-20-20-20 was used for economic reasons back in the day, not for any sound decision. To get close to vintage with series connected caps these days, you would need a couple 80uf 350v caps for the first filter stage, or thereabouts, along with a 220k 1 watt resistor in parallel with each cap. When you connect caps in series, the voltage rating doubles and the microfarad rating halves, so two 80uf 350v caps in series would give the same thing as one 40uf 700v cap. For the second filter stage, a couple 40uf 350v caps in series with the resistors in parallel would do the trick. For the 3rd stage, a 20uf 500v cap would be a good idea. The 4th filter stage can get by with a 450v rated cap. The series connected caps would also need some terminal strips installed with a couple holes drilled into the chassis to hold the parts. The SDS cap board option does not require any holes drilled. Check that out at Triode Electronics. If you do decide to use larger than stock caps in the first couple stages, then you should also change to solid state rectifiers or use a couple Weber Copper Caps WZ34's.

Greg

[n2000s]

Greg, thank you very much for the help and I will look a little deeper into using the series caps or SDS board. I was going to post this over at the sunn.ampage.org site in case anyone over there can also use the info. If you like it might be good to repost your response there as well.

[n2000s]

Thanks! Definitely ruling out nos caps at this point. It's been a great learning reading up here and I might just get into doing some of this work myself.

[soundmasterg]

Greg, thank you very much for the help and I will look a little deeper into using the series caps or SDS board. I was going to post this over at the sunn.ampage.org site in case anyone over there can also use the info. If you like it might be good to repost your response there as well.

That is actually where I meant that you should do a search, as most of the Sunn traffic and my old posts on the subject are there. Just do a search for posts by me and you should find them from a couple years ago on up to the present as it seems to come up often.

Greg