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Old 12th May 2006, 02:07 AM   #1
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Default PS Caps

Howdy, I'm trying to decide on what type of cap to use in a power supply. I've got some new electrolytics the right size (22uF*450 volt) but they are +or- 20% and electrolytic. I guess my question is how important is quality in the power supply? What about motor run oil caps? Photo-flash caps? Anybody got a favorite that won't totally break the bank. I think I have some motor runs but they are Big. I would assume if metal case motor runs are used you have to insulate the case from the chassis. Sounds like a pain All opinions and or suggestions are most welcome. Thank You Kindly, Jay
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Old 12th May 2006, 02:54 AM   #2
arnoldc is offline arnoldc  Philippines
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There was a discussion about this a while back. We listed the caps and our preferences...

Did not turn out in the search?
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Old 12th May 2006, 04:15 AM   #3
kmtang is offline kmtang  Canada
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I like having Blackgate WKZ for the PS bypass. I have tried Motor Run Oil caps, Mundorf TubeCap but I still like Blackgate the best.

Johnny
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Old 12th May 2006, 07:49 AM   #4
lndm is offline lndm  Australia
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Hi Jaymanaa,
The +/- 20% does not necessarily mean these are of poor quality or will sound bad.
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Old 12th May 2006, 10:04 PM   #5
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Originally posted by kmtang
I like having Blackgate WKZ for the PS bypass. I have tried Motor Run Oil caps, Mundorf TubeCap but I still like Blackgate the best.

Johnny

Is there a place to buy them online?


I thought I remembered a thread about this topic, but could not find it with the search. I will try again. I was really trying to get a discussion going about the importance of PS caps. IE: recovery time, tolorences, how PS can add to final sound, etc. I am trying to build a SET EL-34 with very crisp bass response. My very limited knowledge leads me to beleive that overkill in the PS is a good place to start. I'm leaning toward motor run, but they are so big. I would have room if I mount them standing up on the chassis, but if the case has to be insulated from the chassis it will be a little tricky. Maybe they don't have to be. The current production ones I have show no continuity between the case and the terminals. Anybody know? Thanks Jay
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Old 12th May 2006, 11:18 PM   #6
lndm is offline lndm  Australia
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The power supply caps are in the signal path. Some circuits tends to mitigate this to varying degrees, but SET less so. A stage is comprised of a circuit that is a loop formed by a triode, its load and the power supply (primarily a cap). The output is a sampling of this, how could that cap not be in the signal path.

Damping factor plays a part, I don't believe it is the only issue. You might ensure your output impedance is low by bypassing your cathode resistance or using some other method to hold your cathode voltage steady.

Here is a good tutorial on choosing components for a power supply.

http://www.siteswithstyle.com/VoltSe...C_ringing.html
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Old 13th May 2006, 01:03 AM   #7
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Default PS Caps

I prefer using choke input-double or triple pi filter designs. This keeps the CAP size an order of magnitude smaller and speeds up the response.

I don't use a pure choke input--usually add about .3 to .5 mics across the input to keep voltage transients down.

On the scope this type of design is much more responsive than RC filter stages. It's OK to add a big C at the end if it is bypassed, but try to keep the R's out of the DC path if possible.

One other trick I use is to buy medical grade isolation transformers at various voltages [surplus]. This allow setting of output voltage with a little up front design work by twiddling the AC input voltage. Clearly you can't use tube rectifiers in with this technique.
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Old 13th May 2006, 03:10 AM   #8
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Quote:
Is there a place to buy them online?
Blackgates? -> Yes!

Michael Percy
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Other good parts for toob amp:

AES

+/- 20% is good for an electrolytic, lots were made to +80% -20% tol. I've had good results with Panasonic caps (snapmount) from Digi-Key and Cornell Dubilier from Mouser. JJ had some very good caps I've been told. Same with LCR. Blackgates will bust your bank account, but if you got the $$$ go for it.

Cheers
Wayne
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Old 13th May 2006, 07:18 AM   #9
knubie is offline knubie  Norway
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HI, I asked about PSU caps in this thread:

There is a lot of opinions about PSU types, RC, LC and regulated PSU's versus non regulated (tubes and sand) and so on. I trying different things myself when I have got the amp up and going. Now I just have the PSU and a dummy load
I myself concluded to try the ASC Motor Run Caps if 20 or 40mF is enough to get you going. BlackGate's must be for the lordship's and oil baron's
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