Foil vs electrolytic capacitors for tube amplifier power supplies

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#65
Push-pull 2A3 amplifiers in first Hammond organs (1930s) utilized the newly invented electrolytics - 2 x 30 uF - in power supply. After the first 1,000 organs produced, they replaced the electrolytes with much bulkier and much more expensive 8+8+4 uF oil blocks (foil PIO). The oil blocks persisted through 3 decades, saw replacement of 2A3 with 6V6, and gave way back to electrolytes with the introduction of 6BQ5 amplifiers in mid-60s, as a cost- saving measure due to increased competition.
 
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#66
Those nowadays ASC motor oil cap seems not that bad and pretty inexpensive for a MKP cap. For ones liking such caps. Everyone having his own sauce today.

I haven't experienced with power supply caps with HV and but just bougth some low uF Sic Safco 450V and two 120 uF/450V United Chemicon, hopping they are solid enough. Sic Safco, I have no doubt as they were famous in the industrial culture to be very reliable caps and also god sounding from Radio amateurs testimonies.
 
#69
FWIW I added some poly caps as a bypass to the existing electros in my PP OTL tube amps. To my ear the sound change was immediate and obvious. Over the next few hours they developed & smoothed out. I guess I'd describe as quieter in that details particularly in the highs seemed more pronounced and at the same time more natural. As some have commented the deep bass also a little had less bloom, so not all would like it.
This was to +-170V B+. Originally was CLC with around 9mF of electro filter caps. Added some cheap Axon 56uF 250V poly caps as close to the tubes as possible. There already were some 10uF blackgates right on the tube sockets.
 
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#70
I see I previously recommended Kemet DC Link caps, and yes I did prefer them to Clarity caps. But better than those are the Russian KBG caps. Big brown rectangular things - you really have to find space for the them, they're huge. I now put one in first position in all my power supplies, audibly better than anything else I've tried. I follow those with the Kemets, so now no electrolytics in the PSU. Big chokes do a lot of the heavy lifting, so smaller caps. The KBG are 4uF or 6uF. I bought a good supply, but they're not cheap these days.
 
#71
What are your favourites for an electrolytic cap of 450V minimum? I've been looking at these, values 47uF to 100uF:
  • Panasonic EE
  • Vishay 157 PUM-SI or 159 PUL-SI
  • Epcos B43504 or B43501
  • Rubycon HXC or CXW
  • Nichicon GU or KX
  • United Chemicon JXJ
  • Kemet PEH532
  • Wurth WCAP-A13H
  • Unicon LXN
  • Cornell Dubilier SLPX
  • LCR
  • MIEC
  • Mundorf MLYTIC HV

Any others?
 
#72
Cornel Dublier SF (polypro in oil) goes up to 660 VAC and is good for B+ power supply.

Would avoid Vishay from BC ex Philips line that are solid but weird sounding result imo.

If lythic I'd choose long life ones : Rubycon, Pan. Epcos... as main smoothing cap.
 
#73
The caps in this type of power supply are under very little stress. Even cheap caps will probably have a respectable lifespan.

Generally, Epcos, Rubycon, Nichicon, TDK, Kemet, UCC, Panasonic, etc are all fine. The BC / Vishay caps I have used for some beastly power supplies, and they have held up fine, but were rather pricey from what I remember.



Above 450 V, I generally would suggest using either series caps or moving to motor run caps if you can tolerate the lousy energy density. I've paid the extra money for 500 V electrolytics before, and I probably wouldn't do it again. There are better ways to go about the problem.

For this application, don't worry yourself too much with specifics of which series, which brand, etc. Tube amp power supplies are a pretty easy life for an electrolytic, so just about anything from a reputable manufacturer will perform just fine and last long enough to not be a problem.
 
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