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-   -   How much capacitance at the chip when using a large snubber psu? (http://www.diyaudio.com/forums/chip-amps/90796-how-much-capacitance-chip-when-using-large-snubber-psu.html)

Bassterror 21st November 2006 06:17 PM

How much capacitance at the chip when using a large snubber psu?
 
Hi

without snubber i would use 2200 at the Chip.

But how much is needed if you have big caps with snubber ahead of the chip?
Is there any audible advantage of using smaller ones, perhaps 220 or something?



greetings,
Stephan

markiemrboo 21st November 2006 07:57 PM

Quite curious to know this myself. I've got a measily 2x2200uF per chip on each rail, and nothing but the two 100nF caps next to the chip at the moment. Mainly because I haven't really got anything to go next to the chips except 47uF, and 47uF sounds kinda... pointless :) :xeye:

Nordic 21st November 2006 08:11 PM

I think the LM4780 datasheet pcb is a good minimum guide for that whole series of opamps. it has 2 x 100nf close to the positive power pin, and 1 x 100nf to the negative. At a little distance awayare some 100uf caps followed further away by 1000uf...

markiemrboo 21st November 2006 09:05 PM

I'm guessing by further away there, you would mean on the power supply board... if doing it in a sort of "modular" way? Or 1000uF's on the amp boards aswell as 100uF's? :bigeyes:

AndrewT 22nd November 2006 03:04 PM

Hi,
Quote:

Originally posted by Nordic
I think the LM4780 datasheet pcb is a good minimum guide for that whole series of opamps. it has 2 x 100nf close to the positive power pin, and 1 x 100nf to the negative. At a little distance awayare some 100uf caps followed further away by 1000uf...
I think all 7 on Nordic's list are next to the chipamp.

That would make the PSU over that.

jackinnj 22nd November 2006 04:12 PM

2 Attachment(s)
I use 100nF ceramics as close to the power pins as possible, 10uF, then 1000uF -- on the power supply boards I have used 10mF, 22mF and more recently 39mF

National shows 680nF or 470nF near the pins of the LM4702 -- PLUS a cap (680 or 470nF) from the pos to neg rail -- they used polypropylenes here.

Diode snubber -- posted before but perhaps you haven't seen:

Bassterror 23rd November 2006 09:23 AM

Quote:

Diode snubber -- posted before but perhaps you haven't seen:
Never saw that before... I just knew about caps parallel to the diodes.

I think ill try 1000 with 10. Gonna do it peer to peer.


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