PS Capacitance

Puffin · 2nd March 2008, 12:42 PM

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 !

Nuuk · 2nd March 2008, 01:42 PM

If you mean just say 1000 uF on the pins, I'll wager that a majority of GC's are built like that!

Puffin · 2nd March 2008, 02:45 PM

Nuuk. So I detect from your reply that perhaps capacitance on the PS is beneficial/desired ?

leadbelly · 2nd March 2008, 02:52 PM

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?

Nuuk · 2nd March 2008, 03:01 PM

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.

AndrewT · 2nd March 2008, 03:37 PM

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.

Nuuk · 2nd March 2008, 05:25 PM

...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.

Puffin · 2nd March 2008, 05:38 PM

Thanks everyone. Excellent replies and definitely food for thought. I will try just a tranny and rectifiers for the supplies for my bridged monoblocks.

Puffin · 3rd March 2008, 10:17 AM

I have found a very good article on Power Supplies

Here :-

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

2nd March 2008, 12:42 PM	#1
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	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 !

2nd March 2008, 01:42 PM	#2
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	If you mean just say 1000 uF on the pins, I'll wager that a majority of GC's are built like that! __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

2nd March 2008, 03:37 PM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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. __________________ regards Andrew T.

2nd March 2008, 05:25 PM	#7
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	...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. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

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2nd March 2008, 02:45 PM	#3
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	Nuuk. So I detect from your reply that perhaps capacitance on the PS is beneficial/desired ?

2nd March 2008, 05:38 PM	#8
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	Thanks everyone. Excellent replies and definitely food for thought. I will try just a tranny and rectifiers for the supplies for my bridged monoblocks.

3rd March 2008, 10:17 AM	#9
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	I have found a very good article on Power Supplies Here :- http://www.tnt-audio.com/clinica/ssps1_e.html

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