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Help with selecting PS Caps (for LeachAmp)
Help with selecting PS Caps (for LeachAmp)
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Old 23rd January 2004, 07:15 AM   #1
FromageTheDog is offline FromageTheDog  United States
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Question Help with selecting PS Caps (for LeachAmp)

Hi All,

Was hoping that someone would be kind enough to say a few words about capacitors of the enormous type needed for the PS of a power amp (in my case, the Leach Amp).

I've been having a heck of a time trying to track down the suggested Mallory caps (Digi-Key doesn't carry them, and surplussales and apexjr don't seem to have any at the moment). and I'm at a loss as to what alternative I could use.

My question boils down to this:

How do I select a substitute?

I gather the following:
- Must be > 58V rated (as that is the rail +- voltage). I assume this is only a lower bound and anything higher will do.
- Should have capacitance > 8,000uF, suggested 12,000uF. Again, assume this is a lower bound and higher (at least from reading forum posts) seems to be better.
- Should be can type, electrolytic.

I am mystified by such terms as:
- Computer grade -- is this good? Bad?
- snap-in mount. Screw post is self-explanatory; what on earth does snap-in mean? And what does it mean when there are >2 posts on the cap?
- Tolerance -10/+75%. That seems like an enormous range, but is that bad? It seems like +/-20% would be "better" (symmetry?), but I'm clueless here.

Thanks in advance for any help, it would be much appreciated...

- Fromage
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Old 23rd January 2004, 10:40 AM   #2
Jan Dupont is offline Jan Dupont  Denmark
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You can buy the Mallory caps directly from the manufactor
Free Schematic and Service Manual downloads www.audio-circuit.dk, Spare time company (just for fun): www.dupont-audio.com
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Old 23rd January 2004, 10:50 AM   #3
Mad_K is offline Mad_K  Norway
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have a look at the PEH200 from Evox-Rifa as an excellent example for a electrolytic cap for power amps. They are a little more expensive than your ordinary comuter grade caps, but also better..

some grades:

-standard (snap in =snap into pcb)
-computer grade
-industrial (peh200)

don't bother with the tolerances.

more than 2 post are normally just for extra stability when soldered onto a pcb

when selecting a substitute. you are correct; same or higher voltage reating and same or higher capacitance...

hope this helps
Mads K
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Old 23rd January 2004, 10:54 AM   #4
crown300 is offline crown300
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www.newark.com has Mallory Caps, you can use a credit card to order them.
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Old 24th January 2004, 07:14 AM   #5
sma is offline sma  Indonesia
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black gate is the best cap i hear for PS section.the sound is very flat and natural....
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Old 24th January 2004, 07:20 AM   #6
wrl is offline wrl  United States
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I got the 10,000 uf mallory caps from mouser electronics. I think they were like 12 bucks a piece. Ordering is no prob. I am very happy with the sound although I haven't compared them to anything. Good luck with the leach amp.

Anything worth doing is worth doing right... and redoing to make it better... and again to fix it back the way it was.
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Old 25th January 2004, 04:58 AM   #7
FromageTheDog is offline FromageTheDog  United States
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Everyone: Thanks so much for your input! I just can't tell you how encouraging it is to have received so much help so quickly...

Just some individual comments:

ACD: I actually thought of this -- tried going to the Vishay website to see if I could track these items down, but it seems that the PS caps Dr. Leach suggests are no longer in production. Couple this with the fact that the technical info. available on their site is minimal at best, I was up creek no paddle... Or was I looking in the wrong place? I've certainly done this before...

Mad_K: Thanks -- this is exactly the reply I was looking for!

crown300, sma, wrl: Thanks for your suggestions; I will definitely consider these sources and caps in my search for alternatives!

Again, thanks all! Definitely looking forward to begin building!

- Fromage
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Old 7th February 2004, 06:27 AM   #8
tpenguin is offline tpenguin  United States
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Well, I'm not an expert on how power supply caps affect the sound quality of an amp, but I personally don't think super-exotic caps are necessary for PS filtering caps. You just need to know your minimum total capacitance per rail per channel and your maximum rail voltage. Then you start looking to see what's available in your price range. Keep in mind that it is usually better to use a large number of small caps than a small number of large ones. For filtering caps, the tollerance is unimportant (especially the +75%, since if you get extra capacitance in it that you didn't pay for, it's a good thing.) Generally, it's good to look for caps with a lower series resistance, but I don't know how much of a difference that makes, and the only way to tell would be subjective listening tests, in a blind experiment. If you know which caps you're listening to, that will affect your perception of them.

I'm currently building 2-ch leach amp, myself, and I have 4x 10000uF 63V caps total, which is more than adequate, but I like to have the extra capacitance. If you're on a budget like I am, I would recommend you look at {URL=http://www.apexjr.com/capacitorsR.html]these caps[/URL] from apex jr.

Snap-In 1 3/8" X 3 1/8" Nichicon $3.95

They are snap-in, but they'll work just fine standing up with wire soldered to the leads. They aren't exotic, but I don't really think they need to be. Two would probably be ok, but I would really suggest 4. No, I haven't "listened" to these caps (perhaps expecting to hear the ocean?), but they're cheap, and they'll get your amp up and running. If you want something exotic later on, you can swap them out easily, but I doubt that you would notice a difference without knowing the caps were different beforehand. That's just my 00000010 cents.
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Old 7th February 2004, 08:10 AM   #9
FromageTheDog is offline FromageTheDog  United States
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tpenguin -- thanks for the tip! I remember looking at these and not being sure if they were quite up to the task (Prof. Leach recommends 12,000mF caps in his guide). But I'm clueless with these things and have no idea what's "good enough".

Cheapest I've found something viable elsewhere is the 12,000mF Mallory caps at surplussales.com. $17 each. You're suggestion is much more palatable! =)

Thanks again,

- Fromage
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