Vintage Stereo Amplifier Capacitors

July 8, 2017 1:49 PM

I am trying to determine 1) Where to buy capacitors to replace the blown capacitors in my vintage Sansui AU-4400 stereo amplifier, 2) How to find modern day (or deadstock? is deadstock a thing with capacitors? don't laugh!) capacitors that are comparable and appropriate to the original capacitors I am replacing?

I have someone knowledgeable in electronics/soldering who is assisting me in learning and executing the recapping process - so I'm not looking for advice on the process of recapping, nor diagnosing the source of my amp's problems - but I do need help finding websites where I can buy the right replacement capacitors.

I've already tried looking at the Audiokarma forums for this info, but I haven't been successful in finding anything 2017-current about the best place to buy new caps. Or how to demythologize finding replacement capacitors that are the "right fit" for replacing the original capacitors.**

Of note: I am lucky to have the original Sansui AU-4400 service engineer manual- so I do have access to the amp's schematic diagram and parts lists. The problem, of course, is that the Sansui AU-4400 was produced between 1975 and 1976, so the Sansui 'stock numbers' listed in the service manual are, uh, no longer relevant after 40 years.

Also, concerning finding websites where I can buy the capacitors I need, I'm located in the US (should it matter). I'd prefer to buy from suppliers in the US to keep shipping cost low, but am open to non-US suppliers if they have better options.

Thank you in advance for your help!

**I am concerned about the fact that to some extent, if not a significant extent, replacing caps may alter the sound/tonality/warmth of the amplifier. So in other words, what do I need to know to minimize this risk?

posted by nightrecordings to Technology (9 answers total)

I would replace just the electrolytic caps, as other types are much less likely to have gone south. Given that electros are highly unlikely to be in the audio signal path I normally just replace like for like in terms of capacitance and like for like or better in terms of voltage rating, without writing too much.

I generally buy these from element 14 or RS components, both of which are online shops. Element 14 is American but might still be called Farnell for you. I'm not sure if you have access to RS but give it a go. I believe you have some other options as well, including Digi-Key and Mouser.
posted by deadwax at 2:08 PM on July 8, 2017 [2 favorites]

I would have gone Parts-Express for audio capacitors...but it's probably been 10 years since I have ordered from them. Mouser or Digi-Key would have been strong seconds...
posted by NoDef at 2:17 PM on July 8, 2017 [1 favorite]

Affecting sound quality is pretty much unavoidable. Keep in mind the receiver you have now was sounding different from how it did when it was new. And it's probably driving speakers and handling source components that didn't exist when it was manufactured. Stay focused on making it sound how you want it to sound and you can avoid a kind of authenticity rabbit hole that ultimately does nobody any good.

Anyway, yeah: Digi-Key or Mouser are go-to resources. They both primarily deal within the industry so shipping might be relatively high for your order volume, but the prices will be good. Parts Express will have a limited range of audio-specific caps, and prices will be okay. They have occasional sales. Parts Connexion will have audiophile-approved components at audiophile prices.
posted by ardgedee at 2:18 PM on July 8, 2017 [2 favorites]

Newark is another source.
I agree with deadwax, just replace the electrolytics. I always mark the polarity before I remove them to avoid that "oh shit!" moment.
If any are marked NP they are nonpolarized and need to be replaced with nonpolarized (polarity doesn't matter, because they are nonpolarized).
posted by H21 at 2:42 PM on July 8, 2017 [1 favorite]

Also, you can go up in voltage, but not down. Newer capacitors are usually smaller in size, so going up in voltage may cause them to fit better.
posted by H21 at 2:47 PM on July 8, 2017 [1 favorite]

Yep, another vote for "replace the electrolytics, don't worry about them affecting the sound because they probably will not (aside from having your power supply perform better affecting the sound), and don't be surprised if they are much smaller".

Most of the sites that I used for caps have been mentioned, but you can also use octopart.com as a sort of parts search engine that'll let you know who has what in stock and at what price.
posted by destructive cactus at 2:58 PM on July 8, 2017

For the record, while Element14/Farnell are now American owned (Avnet bought the company last year), their American branch is still Newark.

Mostly agree with most of the comments, I'll withhold my opinions on the audiophile aspects, but I'll add that while it's generally OK to go up a step or 2 in voltage rating, it's not a good idea to go too far (e.g. from 50VW to 450VW) - reliability, lifetime, & function will all suffer (e.g. ESR, DF/tan δ, and actual capacitance will increase).

The very general rule of thumb for electrolytics is to spec them for 1.5x~2.5x applied voltage.
posted by Pinback at 5:38 PM on July 8, 2017 [1 favorite]

Oh, and it'd be worth at least checking any poly* film & epoxy-dipped capacitors for DC leakage (needs to be done @ ~rated voltage). Ones from that era are generally OK, but it's not too uncommon to find one or two that have deteriorated somewhat due to sealing failure & subsequent moisture absorption - especially in places where they're subject to higher temps &/or voltages (e.g. in/around the power supply, & near the output stages).

Faulty ones in the signal path will definitely be contributing to overheating/early failure of other components, & likely noticeably affecting sound quality.
posted by Pinback at 6:06 PM on July 8, 2017

is deadstock a thing with capacitors?

It is, actually, although the usual term for electronics is "new old stock" or NOS. Vintage radio and instrument amplifier enthusiasts tend to look for NOS parts, especially vacuum tubes. Whether using said parts has an effect on the sound, or whether the effect is worth the price you pay for NOS parts is . . . . well, let's call it highly debatable. With the exception that some older electronics use tubes or IC's that aren't made anymore, so buying old parts is the only way to repair those pieces.

I wouldn't worry about it in your case, and I'd third Mouser or Digi-key as a source.
posted by soundguy99 at 10:18 PM on July 8, 2017