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Old 5th March 2008, 08:39 AM   #1
CJ900RR is offline CJ900RR  Sweden
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Default Snubber question

Hello fan's of snubbers

When using snubber design on a chipamp, 100-220uF + 0,1uF, is it enough capacitance to use on the pcb itself, or should I ad more capacitance before them on the pcb.

Im designing a board right now and thinking about using 100-220uF + 0,1uF on the pcb before each LM3886, and then use larger cap's in the power section that will be on another pcb. Will it be enough capacitance or should I ad, say 2200-4700uF on the LM-pcb to before the snubbers?

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Old 5th March 2008, 09:33 AM   #2
Nuuk is offline Nuuk  United Kingdom
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100-220 uF is not really enough. You can use up to about 2200 uF without the need for snubbers.

The idea of snubbers is to allow larger amounts of capacitance to be used without the 'harmful' affect that can have on the sound quality. So yes, you can have 2200, 4700, or even 10,000 uF providing they are snubbered.
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Old 5th March 2008, 10:03 AM   #3
CJ900RR is offline CJ900RR  Sweden
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Quote:
Originally posted by Nuuk
100-220 uF is not really enough. You can use up to about 2200 uF without the need for snubbers.

The idea of snubbers is to allow larger amounts of capacitance to be used without the 'harmful' affect that can have on the sound quality. So yes, you can have 2200, 4700, or even 10,000 uF providing they are snubbered.

Hi Nuuk and thank you. Im aware of that I need more capacitance than those 100-200uF, but I want to know if i have to put the bigger cap's on the pcb, or if its enough to have them off-board, in the psu-part of the amp.
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Old 5th March 2008, 10:07 AM   #4
CJ900RR is offline CJ900RR  Sweden
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Or should i do like this...
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Old 5th March 2008, 10:12 AM   #5
Nuuk is offline Nuuk  United Kingdom
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If you have say 220 uF on the pins, then you can place the larger caps 'away' from the amp circuit, ie off the PCB, or even in a separate PSU case.
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Old 5th March 2008, 10:18 AM   #6
AndrewT is offline AndrewT  Scotland
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Put the 100nF on the chipamp power pins.
Put the 220uF next to the chipamp power pins.
Put the 2200uF as close to the chipamp as possible, aim for less than 30mm of track length.
My 2200uF caps have just arrived. 16mm diam by 25mm tall. I intend putting these on the P2P in lieu of the 220uF.
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Old 5th March 2008, 10:30 AM   #7
Nuuk is offline Nuuk  United Kingdom
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Quote:
My 2200uF caps have just arrived. 16mm diam by 25mm tall. I intend putting these on the P2P in lieu of the 220uF.
Panasonic ECA by any chance Andrew?
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Old 5th March 2008, 11:02 AM   #8
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by Nuuk
Panasonic ECA by any chance
no, Forever from Rapidonline.
Never heard of them! but they are cheap 0.33each for 12.
I'm trying Carlos FM's recommendation.
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Old 5th March 2008, 11:12 AM   #9
CJ900RR is offline CJ900RR  Sweden
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Well thank you both of you. I will try to put it as close as possible. Hand-solder the 0,1uF directly on the supply pins must be the best solution i think.

Since the positive supply pins on the LM are internaly connected, pin 1 and 5, do you really need to have a trace to both of them, or can I skip pin nr 5 for a easyer layout?
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Old 5th March 2008, 11:23 AM   #10
Nuuk is offline Nuuk  United Kingdom
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I have never put a cap on pin 5 and it seems to work fine without. (I uses a short wire link between pins 1 and 5).

Quote:
I'm trying Carlos FM's recommendation.
The Ronaldo of Gaincloning!
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