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Old 2nd March 2008, 12:42 PM   #1
Puffin is offline Puffin  United Kingdom
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Default PS Capacitance

I have seen details of a power supply ( for an LM3875 amp) Which simply consists of a tranny and bridge rectifiers. It seems that it only uses the capcitance at the PS pins to smooth the supply.

Any comments anyone ? I'm just about to lash one up to see what it is like. It is simple if nothing else !
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Old 2nd March 2008, 01:42 PM   #2
Nuuk is offline Nuuk  United Kingdom
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If you mean just say 1000 uF on the pins, I'll wager that a majority of GC's are built like that!
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Old 2nd March 2008, 02:45 PM   #3
Puffin is offline Puffin  United Kingdom
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Nuuk. So I detect from your reply that perhaps capacitance on the PS is beneficial/desired ?
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Old 2nd March 2008, 02:52 PM   #4
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Default Re: PS Capacitance

Quote:
Originally posted by Puffin
It seems that it only uses the capcitance at the PS pins to smooth the supply.
I'm not sure that anyone understands what you are trying to say. Are you trying to differentiate between capacitors close to the rectifiers and capacitors close to the chip?
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Old 2nd March 2008, 03:01 PM   #5
Nuuk is offline Nuuk  United Kingdom
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Quote:
Nuuk. So I detect from your reply that perhaps capacitance on the PS is beneficial/desired ?
No, what I meant was the original Gaincard used 1000uF on each power supply pin and none in the PSU. That's how I have built all my GC's with the exception of the regulated ones. I don't like large amounts of capacitance on an unregulated GC.
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Old 2nd March 2008, 03:37 PM   #6
AndrewT is offline AndrewT  Scotland
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Hi,
there are two schools of thought on powering chipamps.

One uses a conventional PSU that supplies low ripple to the chip and the chip has local decoupling close to the chip supply pins.
Carlos FM uses the conventional PSU but with snubbering.

The other camp dispenses with smoothing caps and sends high ripple supplies to the chip amp and lets the local decoupling do as much smoothing as it's able. Peter Daniel, Nuuk & the original Gain card follow this route.
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Old 2nd March 2008, 05:25 PM   #7
Nuuk is offline Nuuk  United Kingdom
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...and of course, a lot depends on the speakers that you are using!

As ever, my advice is to try both and decide for yourself.
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Old 2nd March 2008, 05:38 PM   #8
Puffin is offline Puffin  United Kingdom
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Thanks everyone. Excellent replies and definitely food for thought. I will try just a tranny and rectifiers for the supplies for my bridged monoblocks.
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Old 3rd March 2008, 10:17 AM   #9
Puffin is offline Puffin  United Kingdom
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I have found a very good article on Power Supplies

Here :-

http://www.tnt-audio.com/clinica/ssps1_e.html
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