recommendations on capacitor upgrades

[recstar24]

Hey guys,

I ran the schematic of my moth to dsavistk and he offered some recommendations for a couple of places to upgrade the caps.

Looking for 33uF 450V high quality cap, film for sure. They are cathode bypass caps. Right now there is a solen polypropylene in there, the only thing I could find which may be an improvement is the Obbligato film in oil cap, they have a 30uf and 70uF 630v. All of the really really nice film caps are around the 250v range, which I think might be risky in my amp as the schematic says for 450v, but the actual amount of voltage across that point is probably closer to 250.

Also looking for a 220uF 500v cap upgrade as well that I believe is in the power supply. Figured I would explore some cap options before even thinking about silver output transformer options:p

[luvdunhill]

What's the general topology to need a 250V cathode bypass cap? My recommendation for the PSU would be the _Japanese_ made ASC (made by Shizuki) X386S capacitors, if you can get it to fit.

Edited April 18, 2009 by luvdunhill

[recstar24]

What's the general topology to need a 250V cathode bypass cap? My recommendation for the PSU would be the _Japanese_ made ASC (made by Shizuki) X386S capacitors, if you can get it to fit.

The ASC's were what Doug suggested as well, but would probably have to parallel 2 of the 100uF as I believe that is the biggest they have, and there is space for them to fit for sure as the inside of the moth chassis is massive once you take out the power transformer and make it external.

its SET, DC coupled design, input is 6j5 into 2a3 or 45 tube, output transformer coupled.

[luvdunhill]

Well, in my opinion the Japanese X386S (if you can find them, and.. really, they are big) are probably the equal of the Black Gate WKZ, in circuits that I've tried them (PSU). At this voltage, they are probably one of _the_ caps to beat. I dunno about the cathode bypass caps, as I avoid them where I can and where I cannot, I have pretty small voltage and have found polymer caps to work better than anything I've tried. I don't really have the experience that Doug does here, so I'm sure whatever he recommended would be worth trying. I will say if I had to just try something, since I don't have much experience with this amp, I'd start with a Mundorf M-Tube Cap 47uF/600V or 30uF/600V and bypass it with something like a Relcap RTX.

[luvdunhill]

Just noticed some Japanese ASCs go up for sale, and started wondering what you ever decided to do with your upgrades?

[n_maher]

Just noticed some Japanese ASCs go up for sale, and started wondering what you ever decided to do with your upgrades?

Link via PM?

[luvdunhill]

Link via PM?

They are at the same place you got your variac

[n_maher]

Looks like the guy who I bought the variac from bought them, small world.

[luvdunhill]

Looks like the guy who I bought the variac from bought them, small world.

I don't know if you guys ever buy from this guy, but he has some in stock:

MachMat tube sales

There's also a local guy in Austin that often has them, if you're really interested

edit: heh, here he is in fact. Strange guy... http://www.diyaudio.com/forums/showthread.php?threadid=130519

[Quad]

MachMat sold me crappy capacitors once. I sent them back, but he did not reimburse me fully. Not recommended by me.....

I don't know if you guys ever buy from this guy, but he has some in stock:

MachMat tube sales

There's also a local guy in Austin that often has them, if you're really interested

edit: heh, here he is in fact. Strange guy... diyAudio Forums - Sourcing ASC 100uf X386S capacitor - Page 1