Capacitance to high?

wboyd · 10th March 2006, 05:31 PM

I am in the process of spec'ing out some parts for a p2p gainclone (I am new at building them- but not entirely new to electronics) and was wondering if a pair of 2200uf 50v's would be to high for the rails? BTW, I am using LM3875 chips. I am planning on getting about 35v from the bridge...

Thanks,

Wayne Boyd

Nordic · 10th March 2006, 06:31 PM

Not necceraly too high, although many people like to keep the high capacitance levels in the PSU. If you do use them, you will want to solder 0.1uf foil/polyester caps directly over the leads of each cap.

Bazukaz · 10th March 2006, 06:36 PM

Not too high , really.If it is for two channels , it is probably too low.
A 4700uF for a channel would be just right, and not expensive.

Regards,
Lukas.

Nordic · 10th March 2006, 07:17 PM

Sorry, if he meant for use in the PSU, then yes I think it is too little...

PauSim · 10th March 2006, 07:23 PM

If it is specifically a gainclone and not a (different) chipamp, 2200uf is what the 50w Gaincard uses...

elementx · 14th March 2006, 01:00 PM

4700uf/channel is the way to go.

jackinnj · 14th March 2006, 01:56 PM

you can't just pick a number out of the air -- the size of the capacitance will determine how much the power supply voltage droops under load -- here's a hint -- the chip will take 7 amps max before protection sets in -- with a 60 Hz power supply the diode is "ON" for about 7.5 milliseconds --

the voltage droop (peak to peak ripple) is (approximately) given by the following equation:

E = I * t / C

with 10,000 uF on each supply rail the droop will be a little more than 5 volts at the point at which protection kicks in.

i've used 10,000 to 39,000 and 10,000 seems to be the best choice between economy, size and performance -- the THD tests I ran were all based upon a supply with 10,000uF/63 V Nicchicons. If you had to run an LM4702 for an industrial or laboratory application I would choose 22,000uF.

Dominick22 · 14th March 2006, 04:00 PM

jackinnj,

I am curious to know which Nichicons you used?

I just bought the 10,000uf Super Through Nichicons and have yet to get a lengthy chance to listen to them. Its good to hear that you view this as an improvement though.

Dominick

wboyd · 14th March 2006, 04:10 PM

jackinnj,

Thanks for clrifying that for me. I was unsure exactly what the effects would be going too high or too low.

everyone,

I have built one of the kits and that worked well...but I thought that I would try my hand at a nice p2p version with more "high-end" components. Saving the money for the components rather than spending it on a kit of some sort. I have read many threads on the subject, here and on other forums and have stttled on a design, components and a nice chasis.

I would also appreciate everyones suggestions for components.

thanks,

Wayne

jackinnj · 14th March 2006, 04:54 PM

Quote:

Originally posted by Dominick22
jackinnj,

I am curious to know which Nichicons you used?

I just bought the 10,000uf Super Through Nichicons and have yet to get a lengthy chance to listen to them. Its good to hear that you view this as an improvement though.

Dominick

I used the low profile ones -- i use low profile electrolytics in my tube stuff as well.

10th March 2006, 05:31 PM	#1
wboyd diyAudio Member Join Date: Aug 2004 Location: Louisville, KY	Capacitance to high? I am in the process of spec'ing out some parts for a p2p gainclone (I am new at building them- but not entirely new to electronics) and was wondering if a pair of 2200uf 50v's would be to high for the rails? BTW, I am using LM3875 chips. I am planning on getting about 35v from the bridge... Thanks, Wayne Boyd __________________ "I am always doing that which I cannot do, in order that I may learn how to do it"

10th March 2006, 07:23 PM	#5
PauSim diyAudio Member Join Date: Jan 2004 Location: Portugal	If it is specifically a gainclone and not a (different) chipamp, 2200uf is what the 50w Gaincard uses... __________________ Paulo

14th March 2006, 04:00 PM	#8
Dominick22 diyAudio Member Join Date: Aug 2005	jackinnj, I am curious to know which Nichicons you used? I just bought the 10,000uf Super Through Nichicons and have yet to get a lengthy chance to listen to them. Its good to hear that you view this as an improvement though. Dominick __________________ A real amateur enthusiast!

14th March 2006, 04:10 PM	#9
wboyd diyAudio Member Join Date: Aug 2004 Location: Louisville, KY	jackinnj, Thanks for clrifying that for me. I was unsure exactly what the effects would be going too high or too low. everyone, I have built one of the kits and that worked well...but I thought that I would try my hand at a nice p2p version with more "high-end" components. Saving the money for the components rather than spending it on a kit of some sort. I have read many threads on the subject, here and on other forums and have stttled on a design, components and a nice chasis. I would also appreciate everyones suggestions for components. thanks, Wayne __________________ "I am always doing that which I cannot do, in order that I may learn how to do it"

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10th March 2006, 06:31 PM	#2
Nordic diyAudio Member Join Date: Sep 2005	Not necceraly too high, although many people like to keep the high capacitance levels in the PSU. If you do use them, you will want to solder 0.1uf foil/polyester caps directly over the leads of each cap.

10th March 2006, 06:36 PM	#3
Bazukaz diyAudio Member Join Date: Nov 2005 Location: Vilnius	Not too high , really.If it is for two channels , it is probably too low. A 4700uF for a channel would be just right, and not expensive. Regards, Lukas.

10th March 2006, 07:17 PM	#4
Nordic diyAudio Member Join Date: Sep 2005	Sorry, if he meant for use in the PSU, then yes I think it is too little...

14th March 2006, 01:00 PM	#6
elementx diyAudio Member Join Date: Jul 2005 Location: cleveland, ohio	4700uf/channel is the way to go.

14th March 2006, 01:56 PM	#7
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	you can't just pick a number out of the air -- the size of the capacitance will determine how much the power supply voltage droops under load -- here's a hint -- the chip will take 7 amps max before protection sets in -- with a 60 Hz power supply the diode is "ON" for about 7.5 milliseconds -- the voltage droop (peak to peak ripple) is (approximately) given by the following equation: E = I * t / C with 10,000 uF on each supply rail the droop will be a little more than 5 volts at the point at which protection kicks in. i've used 10,000 to 39,000 and 10,000 seems to be the best choice between economy, size and performance -- the THD tests I ran were all based upon a supply with 10,000uF/63 V Nicchicons. If you had to run an LM4702 for an industrial or laboratory application I would choose 22,000uF.

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