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Old 1st December 2007, 10:46 PM   #1
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Question big caps power supply?

Hello guys!. Well I have seen some "Gainclones" and some of them use 'BIG" capacitors in the power supply I used 10 mf 50v (LM3875).and 1000mf 50v in the boards that have the LM3875(I do not know how you call that board).I saw this board in Audio-sector "Peter Daniel",and they use 4.7mf 50v in the power supply. my questions are:

a) What is the difference between the ones using small caps and the ones using big caps in the power supply?.

b) is it important the quality of the 10mf 50v in the power supply?

c) since I have "Black Gates" 1000mf 50v in the boards with the LM3875,should I use "Black Gate" 10mf 50v or 4.7mf 50v in the power supply too?.

thank you guys!
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Old 2nd December 2007, 02:15 AM   #2
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Default Re: big caps power supply?

Quote:
Originally posted by lanchile07
Hello guys!. Well I have seen some "Gainclones" and some of them use 'BIG" capacitors in the power supply I used 10 mf 50v (LM3875).and 1000mf 50v in the boards that have the LM3875(I do not know how you call that board).I saw this board in Audio-sector "Peter Daniel",and they use 4.7mf 50v in the power supply. my questions are:

a) What is the difference between the ones using small caps and the ones using big caps in the power supply?.
Small caps are OK if you want the amp to sound like a cheesy transistor radio that can't play low frequencies at any volume level without clipping.

Quote:
b) is it important the quality of the 10mf 50v in the power supply?
Since you have Black Gate caps, I suspect you have already answered that question for yourself. I don't think it matters, and I wouldn't spend the extra money, but you'll find plenty of people who argue in favor of the more expensive caps.


Quote:
c) since I have "Black Gates" 1000mf 50v in the boards with the LM3875,should I use "Black Gate" 10mf 50v or 4.7mf 50v in the power supply too?.
See above.

I_F
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Old 2nd December 2007, 02:59 AM   #3
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Question Gainclone sounds like a Cheesy Radio?

"Small caps are OK if you want the amp to sound like a cheesy transistor radio that can't play low frequencies at any volume level without clipping"

So,are you saying that "Peter" Gainclones sound like a cheap radio?.
Because I got all the parts from Peter.there are many people here that have gotten these kits from Peter and they have the same configuration as mine.

Do you have or ever hear a Gainclone using these parts?
I asked you this question because ,I do not think you have!.
the sound is never like a " CHEESY RADIO".

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Old 2nd December 2007, 03:00 AM   #4
BWRX is offline BWRX  United States
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Default Re: big caps power supply?

In addition to I_Forgot's comments, here are some of mine.

Quote:
Originally posted by lanchile07
a) What is the difference between the ones using small caps and the ones using big caps in the power supply?
The value of the capacitors you should use in an unregulated transformer based supply should be sized to provide the amplifier circuit with reasonably ripple free DC supply rails. Generally speaking, the smaller the cap the higher the supply ripple voltage, especially when more current is drawn from the supply. Don't forget that the size of the transformer is just as important as the size of the caps, since it charges the caps.

Quote:
b) is it important the quality of the 10mf 50v in the power supply?
The quality of the caps closest to the supply pins of the chip is more important than bulk electrolytics directly after the rectifiers. Use good quality parts for the large value electrolytics and they'll be fine.

Quote:
c) since I have "Black Gates" 1000mf 50v in the boards with the LM3875,should I use "Black Gate" 10mf 50v or 4.7mf 50v in the power supply too?.
By "mF" you mean microfarad, which is more correctly abbreviated uF. Regardless, it won't hurt to use the small value caps in the supply, but they probably won't make much difference being in parallel with the much larger 1000uF on the boards.
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Old 2nd December 2007, 03:10 AM   #5
Salas is offline Salas  Greece
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Trans & cap relationship is a valuable tool for tuning subjective tone. Don't be dogmatic about it, I F.
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Old 2nd December 2007, 03:40 AM   #6
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Quote:
Originally posted by salas
Trans & cap relationship is a valuable tool for tuning subjective tone. Don't be dogmatic about it, I F.
Right you are! If you like an amp that can't play low frequencies loudly without distorting, by all means use a too-small transformer and too-small capacitors. You are free to choose!

In my dogmatic way, I prefer an amp that can reproduce the input signal with minimal distortion at whatever volume I choose to listen. If I want some change in the sound, I can add a tone control circuit. In my dogmatic philosophy, it is better to start with a good signal and add controlled, predictable amounts and types of distortion than to add unpredictable and uncontrollable distortion to the signal and hope that it comes out listenable.

Woof!

I_F
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Old 2nd December 2007, 03:48 AM   #7
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Well,I am using Plitron 320va and the secondary are 22vac,but I see on the bridge rectifier board there are two 10uf 50v capacitors and two 1000 uf 50 on the chip board(LM3875).but some people use bigger caps on the bridge rectifier.
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Old 2nd December 2007, 03:58 AM   #8
Salas is offline Salas  Greece
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Quote:
Originally posted by I_Forgot


Right you are! If you like an amp that can't play low frequencies loudly without distorting, by all means use a too-small transformer and too-small capacitors. You are free to choose!

In my dogmatic way, I prefer an amp that can reproduce the input signal with minimal distortion at whatever volume I choose to listen. If I want some change in the sound, I can add a tone control circuit. In my dogmatic philosophy, it is better to start with a good signal and add controlled, predictable amounts and types of distortion than to add unpredictable and uncontrollable distortion to the signal and hope that it comes out listenable.

Woof!

I_F
These chip amps we talk about ain't no big canons. Not my cap of tea, I have put together a couple though, and the guys are right, they sound fresh with small designer PSU caps at least. With big ones they lose all character and sound bland. They don't meet several other criteria so they need their salt n' peppa so to speak.
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Old 2nd December 2007, 04:09 AM   #9
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Sometimes it's useful to carry an idea to extremes. Have you ever heard any audiophile say, "Darn, this sounds lousy because I made the power supply way too big and stable."? IMO, it's a problem if the power switch keeps burning up because of the startup surge. Or the bridge constantly fails. Or maybe it's a problem if the system plays for fifteen minutes on stored charge after turning it off!

OTOH, there's no question that too small a transformer and too little capacitance can reduce the power output and potentially degrade the sound due to ripple. So the $64 question is, where to stop? The common rules of power supply design like 1000uF per amp of output aren't too useful, since audio is a transient situation. One of the nicest sounding amps I have, about 50W/ch uses 8400uF on each side of the supply. Another similar one I "upgraded" to 19000uF per side, and it really didn't make much difference soundwise. IMO, 3000 to 10000uF per side is reasonable for 50W/ch amps, though I have nothing math-wise to back it up.
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Old 2nd December 2007, 05:46 AM   #10
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I'm a fan of big beefy power supplies.
Big trans,and lots of capacitance.
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