[mulveling]

I have this Singlepower SDS "toaster" prototype amp that is some 20 years old. I'm aware of the safety warnings concerning these amps. Around 2009, it had upgrades which included Rubycon Black Gate output caps. There are 4 each of the following coupling caps on output:
Blackgate WK POWER TANK: 220uF, 200 WV (Working Volts) rating, Non-Polarized Electrolytic, 30mm Diameter x 25 mm Length

IIRC each audio channel has 2 of these wired, in SERIES, to cover 400 working volts (the tube plate voltage) - any lower rating will absolutely not work. These Black Gates are now completely un-obtainum. I also recall they sounded a LOT better than other electrolytics. This particular amp has been completely reliable & without problem. But as it's ageing, I wonder about my options for replacing those caps, without reducing sound quality. I'm also just curious what the options today look like. There's room for slightly larger caps, but not too much larger.

Would something like a Mundorf Mcap Evo Aluminum / Oil be a good idea? They go up to 100uF @ 350 Vdc, and it's a film cap that's actually small enough in size to work here. If I only use high impedance headphones with the amp (> 300 ohms), then 100uF should be enough. Or, what about the Audio Note KAISEI electrolytics (by Rubycon), which have a 220uF 350Vdc model? Does that look like the most direct replacement for my Black Gates?

Or are there any other ideas I should look into?

Pictured is the OTHER prototype SDS I used to own (this one is very similar but slightly different). The old one shows its two "upstream" Black Gates have been replaced by plain Nichicon 390uF @ 400 WV. Yes, there was a "not nice" reason they were replaced . The two downstream Black Gates remain. All 4 output caps can be seen zip-tied to the bottom rail. The Nichicons are larger and brown.

I know this is crappy work; just looking for opinions on caps please

 

[Tjj226 Angel]

I have tried several mundorf caps in several projects and none of them sound good.

You should take a look at temco motor run caps. They are oil filled film caps that sound better than a lot of name brand caps. With the money you save, you could get a second 1uf cap to put in parallel with them. A temco with a russian paper in oil cap in parallel is what I use in my speakers and it sounds way better than even some of the clarity caps I have tried.

 

[mulveling]

I have tried several mundorf caps in several projects and none of them sound good.

You should take a look at temco motor run caps. They are oil filled film caps that sound better than a lot of name brand caps. With the money you save, you could get a second 1uf cap to put in parallel with them. A temco with a russian paper in oil cap in parallel is what I use in my speakers and it sounds way better than even some of the clarity caps I have tried.

Thanks! I have some Rogue Audio gear with upgraded Mundorf EVO Silver / Oil / Gold caps, and I've got a sneaking suspicion I simply don't like the tonality of those caps. I'll look at the Temcos for an appropriate fit.

 

[tomb]

Hi mulveling! I hope things are going well for you, other than this issue.

Sonic craft (http://www.soniccraft.com) has the Mundorfs (EVO Aluminum oil) all the way to 220uf, for only $97.99 (compared to $150 each for 100uf at PartsConnexion!). They're on Closeout! with him, so you if you call, you may find out he doesn't have enough. It's definitely worth a try, though.

If that's the case. also check out "amplifier_surgery" seller on ebay. I've purchased Mundorf EVO caps in volume from him before. It's been a few years and it appears he has nothing for sale on ebay at the moment. Although he has note saying, "We hope to see you again soon!" that's dated 5/9/2022, which is pretty current. His prices were always outstanding regarding the Mundorf caps. He might respond if you contact him with an ebay PM.

You should stick with 220uf minimum, if you can, because with all the expense involved, it'd be nice to maintain absolutely the lowest bass response. My numbers show that a 300 ohm headphone will drop 0.3dB at 20Hz, whereas 220uf only drops 0.06dB, so almost an entire magnitude of improvement. Keep in mind that harmonic phase differences can still affect the response much higher in the audio band. Again, this is to maintain absolutely the finest performance, which I think you are interested in achieving. Of course, low impedance phones are out of the question. Even with 220uf, you're down -5.5dB at 20Hz with 32 ohms.

As for Tjj226 Angel's comment on Mundorfs, I'm sorry, but ANY film cap is better than an electrolytic, no matter how high-quality (even Black Gates!) the electrolytic is supposed to be. So, I would definitely expect an improvement over the Black Gates, not a step backward instead. You are going to be limited with film caps in finding anything that big. I am frankly shocked that Mundorf made them with that many microfarads. I didn't know that and have bought Mundorfs for years. They are very high-quality audio film caps. The only thing I've noticed to their detriment is a somewhat lean, sometimes metallic sheen to their sound. In many cases, rich, thick, tubey-sounding amps will benefit from the Mundorfs. In any event, your choices are limited (see the next paragraph) and as I said before, any film cap will sound light-years better than an electrolytic.

Also, a quick check at Grainger reveals no motor run caps even approaching 100uf:
https://www.grainger.com/search/mot...earchQuery=motor+run+capacitor&searchBar=true
Do not get these confused with motor start capacitors. Motor start capacitors are very cheap-*ss electrolytics that will sound absolutely horrible.

Good luck and let me know if you need more help!

 

[kevin gilmore]

2 x 220uf caps in series is 110uf.
mouser has a number of 450v rated 100uf film caps at rational prices. definitely will fit inside the box.
And last forever.
black gate caps seem to die after about 10 years.

 

[Tjj226 Angel]

As for Tjj226 Angel's comment on Mundorfs, I'm sorry, but ANY film cap is better than an electrolytic, no matter how high-quality (even Black Gates!) the electrolytic is supposed to be. So, I would definitely expect an improvement over the Black Gates, not a step backward instead. You are going to be limited with film caps in finding anything that big. I am frankly shocked that Mundorf made them with that many microfarads. I didn't know that and have bought Mundorfs for years. They are very high-quality audio film caps. The only thing I've noticed to their detriment is a somewhat lean, sometimes metallic sheen to their sound. In many cases, rich, thick, tubey-sounding amps will benefit from the Mundorfs. In any event, your choices are limited (see the next paragraph) and as I said before, any film cap will sound light-years better than an electrolytic.

Maybe I am confused or something, but what part of what I said makes you think I wouldn't agree that film caps are better than electrolytic.

All I said was to not waste his money on mundorfs and suggested that he take a look at temco caps.

 

[tomb]

Maybe I am confused or something, but what part of what I said makes you think I wouldn't agree that film caps are better than electrolytic.

All I said was to not waste his money on mundorfs and suggested that he take a look at temco caps.

Fine. That's still contradictory in language. Why is a Mundorf a "waste [of] his money" if it's the alternative to an electrolytic?

Looking at Temco's website, the highest uf rating they appear to have is 100uf. Those caps are almost 5-1/2 inches tall by 2-1/2 inches in diameter. Granted, they're super inexpensive, but they're never going to fit into his casework in a safe manner. Routing around a bunch of air-wiring to connect to the terminals of several of those things at 400V(!) would not be my first choice, either.