PSU capacitors setup?

Wagener · 12th April 2004, 08:24 PM

I need to build a PSU for a 4-channel leach amp that will run 4-ohm loads. Leach amp is rated 120W into 8-ohms per channel

Suggested capacitors is one 12,000uF per rail for one channel

It seems that I will need 12,000 uF x 2 x 4 channels = 8 12,000 uF caps?

Do I need to add more caps if I want to run the leach amp into 4-ohm loads?

Main Question - what is the least expensive cap setup (eg. 3 x 4000uf) - I don't mind soldering a lot of caps together.

Solid Snake · 12th April 2004, 08:48 PM

Larger caps will help in transients but they won't save your amp the grief of running continuously into 4 ohms if it wasn't designed for it.

Wagener · 12th April 2004, 09:46 PM

the leach amp was design to handle loads down to 2-ohms. Although not recommended. So I suppose 4-ohms is fine.

I still don't know whether I should have a seperate toroid and psu for each of the 4 channels

sam9 · 12th April 2004, 10:14 PM

"Main Question - what is the least expensive cap setup (eg. 3 x 4000uf) - I don't mind soldering a lot of caps together."

When I've tried to resolve that, it turned out that going either way cost about the same - at least so long as I worked from a catalog such as Mouser or Digikey. If, I could find the right values at tyhre local sdurplus shop then a bunch of smaller caps was somewhat cheaper. What the choice usually comes down to is the height of the enclosure - large screw mount caps have a smaller footprint, I use them is the enclusure is tall enough for them as it make the rest of the component easier ti squeeze in.

"I still don't know whether I should have a seperate toroid and psu for each of the 4 channels"

That may end up being decided by the VA ratings. If you are planning to be driving 4-ohm loads, you may find locating the right size transformer to use for all four is a problem. In which case you will be forced in to using at least two.

I suspect that pratical concerns with respect to the size of the enclosure may play a bigger role than just audiophillic concerns. I keep re-dioscovering that no matter how well I plan a larger enclosure would have been easier to work with.

K-amps · 13th April 2004, 03:34 AM

Also look at the ESR ratings of the caps. Assuming similar ESR ratings for the small and large caps, in that case you will have an advantage in soldering up the smaller caps in paralell as your ESR value will be 4 times less.

To some, thats a huge advantage.

12th April 2004, 08:24 PM	#1
Wagener diyAudio Member Join Date: Mar 2004 Location: Paarl	PSU capacitors setup? I need to build a PSU for a 4-channel leach amp that will run 4-ohm loads. Leach amp is rated 120W into 8-ohms per channel Suggested capacitors is one 12,000uF per rail for one channel It seems that I will need 12,000 uF x 2 x 4 channels = 8 12,000 uF caps? Do I need to add more caps if I want to run the leach amp into 4-ohm loads? Main Question - what is the least expensive cap setup (eg. 3 x 4000uf) - I don't mind soldering a lot of caps together.

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12th April 2004, 08:48 PM	#2
Solid Snake diyAudio Member Join Date: Feb 2003	Larger caps will help in transients but they won't save your amp the grief of running continuously into 4 ohms if it wasn't designed for it.

12th April 2004, 09:46 PM	#3
Wagener diyAudio Member Join Date: Mar 2004 Location: Paarl	the leach amp was design to handle loads down to 2-ohms. Although not recommended. So I suppose 4-ohms is fine. I still don't know whether I should have a seperate toroid and psu for each of the 4 channels

12th April 2004, 10:14 PM	#4
sam9 diyAudio Member Join Date: Jun 2002 Location: Left Coast	"Main Question - what is the least expensive cap setup (eg. 3 x 4000uf) - I don't mind soldering a lot of caps together." When I've tried to resolve that, it turned out that going either way cost about the same - at least so long as I worked from a catalog such as Mouser or Digikey. If, I could find the right values at tyhre local sdurplus shop then a bunch of smaller caps was somewhat cheaper. What the choice usually comes down to is the height of the enclosure - large screw mount caps have a smaller footprint, I use them is the enclusure is tall enough for them as it make the rest of the component easier ti squeeze in. "I still don't know whether I should have a seperate toroid and psu for each of the 4 channels" That may end up being decided by the VA ratings. If you are planning to be driving 4-ohm loads, you may find locating the right size transformer to use for all four is a problem. In which case you will be forced in to using at least two. I suspect that pratical concerns with respect to the size of the enclosure may play a bigger role than just audiophillic concerns. I keep re-dioscovering that no matter how well I plan a larger enclosure would have been easier to work with.

13th April 2004, 03:34 AM	#5
K-amps diyAudio Member Join Date: Nov 2003 Location: Indiana	Also look at the ESR ratings of the caps. Assuming similar ESR ratings for the small and large caps, in that case you will have an advantage in soldering up the smaller caps in paralell as your ESR value will be 4 times less. To some, thats a huge advantage.

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