MC225 Bumble Bee cap replacements?

[goldear]

I'm planning on replacing the bumble bee caps in my MC225. Is there any advantage to sticking with PIO caps as the replacements, or will I change the sound significantly with some good film caps?

I'm not a huge fan of many polypropylene caps as they can sometimes be a little brash sounding to my ear.

I'm presently only really considering two caps: Either some russian PIO caps (which I have no idea how long these can be expected to last), or just use my old standbys, Multicap RTX (polystyrene foil caps).

Do any of you guys have some recommendations for caps which work really well inside of one of these amps (and won't break the bank)? I really don't want to change the sound much. I mostly just want to restore it, rather than attempt to improve it the sound.

 

[goldear]

Seriously, nobody has an opinion on this?

 

[sony6060]

I have an opinion.

I rebuild amps, mainly Fishers. It is no secret every rebuilt Fisher per the customer becomes a stellar performer. Beyond using the best tubes, the secret is using paper/oil caps.

There is a site that shows various types of capacitors and the distortion on a oscilloscope. The paper/oil types have the least distortion of all types tested.

A mix of Russian K40Y-9 and Sprague Vitamin Q coupling capacitors makes for a refined sound. Using all K40Y-9 can be a little harsh and all Vit Q a little soft sounding. K40Y-9 are very dynamic sounding and the Vit Q adds some refinement.

I trust the NOS Sprague Vitamin Q and K40Y-9 as the capacitors are glass sealed. I suspect, like the paper/oil power supply caps that still perform from the 1930s, the Vit Q and K40Y-9 are at least 100 year life capacitors.

 

[mibag6]

Probably lots of opinions on these but if other people had the same problem I did last night they couldn't even get on the site. As far as I know, the Russian PIOs are fine but I'd drop Terry Dewick a line and see what he recommends.

 

[Dukiedook]

Mix and match some Russian PIO with some other caps you like the sound of.
So far it worked on my heathkit W4AM amps when I recapped them with Solen and K40Y-9 caps.
I guess the word is don't use one type for all the caps.

 

[Lman]

I used the Russian PIO's in my rebuild and the amp sounds great to my ears.

 

[shelby1420]

Love the Multicaps but in critical spots, Mundorf Silver and Gold for me!!!!

 

[diamondsouled]

A mix of K40Ys and Vitamin Qs as 60/60 suggests. There are other American manufactured hermetically sealed paper and oil caps that would fit the bill as well: West-Cap, Gudemen, Pyramid, Goodall, etc....

 

[chinacave]

"There is a site that shows various types of capacitors and the distortion on a oscilloscope. The paper/oil types have the least distortion of all types tested."

I would love to learn of this site!

 

[goldear]

I'm not sure that I need to do any mixing and matching here since I'm already I'm leaving the original redish-brown mylar caps alone. They should add their own flavor to the sound. I'm only replacing a total of probably 6 or 7 bumble bees. So whatever I put in there is already going to be mixed with the original mylars.

 

[Steve O]

"There is a site that shows various types of capacitors and the distortion on a oscilloscope. The paper/oil types have the least distortion of all types tested."

I would love to learn of this site!

The site you seek is probably where Steve Bench now resides. The link goes directly to his cap tests.

He's not entirely clear about the parameter he's testing but it appears to be voltage coefficient of capacitance. What this has to do with audio quality is unclear. Ultimately, he finds The PIO caps he's testing for a client to be "best". Personally, I find the results dubious because the audibility of parameter he tests for isn't well documented and the "winner" is a client. You may find otherwise.

Steve Bench's cap test pages at jacmusic

 

[bobrown14]

I build my own amps so can't comment on your MC225 amp but I like the K40y-9 for coupling caps and also use Jantzen Z-Superiors and Mundorf Supreme Golds as well for coupling. None of those will break your bank. I probably prefer the K40y-9 but there's a break in period (say 50 hrs), so patience is key if you decide to try them. Break in is not subtle either. The others I mentioned not much break in but are not PIO.

Despite my 3 favorites I'm not a big fan of boutique caps. Currently I have stashes of the K40y-9, Jantzen Z-superiors, K73-16 and K75-10 (PIOs and good ones), you could try the K75-10 caps if you want a nice sounding PIO cap and dont want to worry much about space.

Cheers,
Bob