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jarthel 21st May 2006 12:37 AM

no metallized caps instead of electrolytics in a tube rectifier power supply?
has anyone tried it?

someone recently sent me a schematic of a supply that uses 30uF metallized caps.

I was surprised as my limited knowledge though I need to use electrolytics for power supplies.

any thoughts on this?

thank you for the replies

lndm 21st May 2006 06:39 AM

Once you've tried it you may not want to go back :D

jarthel 21st May 2006 07:34 AM


Originally posted by lndm
Once you've tried it you may not want to go back :D

With your reply, I'm assuming you've tried it. is the difference that big?

lndm 21st May 2006 08:09 AM

There are good and bad examples of each type of cap, naturally. But in my experience, the difference is definately worth it.

For one thing, many electrolytics I have tried seem to have subtle resonance issues in the upper midrange when used in my amps. The film caps seem to be better in this respect.

Also, when using the film caps, they seem to open up the sound. They seem to give it a higher level of clarity.

The circuits I build are typically sensitive to the power supply and your mileage may vary. I also use motor run caps.

AndrewT 21st May 2006 08:10 AM

my best pre-amp is a solid state with no ICs and NO ELECTROLYTICS anywhere.

I think the main reason it sounds so good is film caps everywhere.

I am looking for a compact film cap to replace the smoothing cap in my Croft Micro II special. Hoping for great things.

jarthel 21st May 2006 12:25 PM

to Indm
where do you get motor run caps in oz?


lndm 21st May 2006 01:07 PM

I was lucky enough to raid my local Tandy whilst they were going out of business. The owner had some non standard stuff in the back room he had on clearance. I use these in my speaker crossovers too.

Jaycar sells some caps that they call motor start caps (p52, 2006 cat). From what I have read, these appear more like motor run caps. Anyway, I think they sound better than electrolytics typically do, and for the price, you don't have too much to lose. :)

jarthel 21st May 2006 01:11 PM

I was looking at some photos of Ducati caps and it seems they have a "screw" at the top.

can these be cut?

jarthel 21st May 2006 01:14 PM

found some nice ASC polypro/oil caps. are these the same as motor runs?

lndm 21st May 2006 01:23 PM

AFAIK, they will offer similar advantages, partly because AFAIK, they are polypropylene in oil. No doubt these are made for heavy current, but the motor runs I have dissected used foil, not metallised film. Still though, I have heard others speak highly of ASC caps.

About the screw, I have a large MKP in a similar looking package with a screw mount like this. The cap is potted. I don't think the screw can be removed without sawing or damaging the package.

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