Replacing electrolytic caps

[Braga]

Hi there,
I´m restoring a Sonic Frontiers SFS 40 tube power amp and has come to my mind if can i replace all electrolytic caps for polypropylene capacitors ?
All except for the main caps .
Will be 6 X 10uf/450V Rubycon caps replaced by Solen or SCR polyprop.
Advise would be very appreciated !
Many thanks,
Braga

 

[gingertube]

Electrolytic caps can certainly be replaced by polypropylene or other film capacitors and will give sonic improvements. The problem is that that the film capacitor of the same value is so much larger than the electrolytic it replaces, and so mechanical fit usually defeats us.
You can "cheat" a little in that you can generally get away with replacing an electrolytic with a film capacitor of about half the value.

Hope this helps.
Cheers,
Ian

 

[Braga]

These caps are located in the regulator, no electrolytic caps in drive stage and power stage.
Many thanks Ian

 

[Fulci]

You can "cheat" a little in that you can generally get away with replacing an electrolytic with a film capacitor of about half the value.
Ian

Hi Ian! Can you elaborate a little more on this matter? I want to replace a few 4,7uF both in the pre-amp and the power amp section of my SS amp. Is that safe, I won't have any problems?

Should I get much of an improvement to justify the extra cost for replacing something like an Elna Silmic or Nichicon KZ with... Mundorf MKP, Clarity Cap ESA, Ampohm FP-CA-AU or similar? These cost about 10x at least more than the ELNAs and are much much larger, I'd need a lot of work to make them fit.

 

[indianajo]

I have used "film dielectric" motor capacitors to replace 42 year old 50 uf 450 V electrolytic capacitors in my Hammond organ. I used genelec 50 uf 600 VAC capacitors. The show a 1000 VDC rating on the device, but not on the farnell website where I bought them. I had to install a different chassis to cover the capacitor terminals, and I ran twinax between the two chassis to eliminate hum pickup. This organ has choke protection of the 5AR4 rectifier, and I have had no trouble with flashover. The organ is about 2x louder than it was before those two capacitors replaced, and is very hard hitting for a 30W +13W +13W tube amp. Schematics are under the H100 on archive.org. Additional capacitors replaced with conventional electrolytic capacitors quadrupled the volume again, and reactivated several dead features such as "percussion" and "string bass". It has been 2 years since I did this replacement, and have had no problems.
I replaced 10 uf 50V electrolytic capacitors in the preamps of this organ with polyethylene caps where they would fit, and aerovox gold 50v ceramic caps where the film ones wouldn't fit. While there are lots of dire warnings about microphonic ceramic capacitors and distortion, I find each cap I replaced improved the sound. This organ does not create frequencies higher than 7000 hz. The signals on the ceramic caps are roughly 25 mv for one tone, or up to 11 times as high if all 11 drawbars are pulled out. The 10 uf capacitors I used were Vishay "ERO" polyester.