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Einric 24th May 2011 03:46 AM

LM4780 Power Supply Capacitor
I have built an audiosector LM4780 kit and I am very pleased with the outcome. I am now looking to upgrade the kit and I am thinking about increasing the PSU capacitors. I was considering using between 2200uf & 6800uf but I'm not really sure which one would be the best choice. I obviously don't want to spend $200 on capacitors but maybe a more reasonable $30.
What do you guys think?


wintermute 25th May 2011 02:59 PM

This is the second time today I've posted this link ;)

My original power-supply had 1X 1000uF panasonic FC per rail per channel. I added an additional 4700uF / rail / channel Nichicon FW. This did reduce the noise on the output (which was already very low).

I'm not able to comment on any sonic differences, as I do not trust my ability to remember before and after comparisons. I struggle to pick a difference with A/B comparisons (when not even blind) on things that most people (who can hear differences) would claim to be night and day!


Einric 25th May 2011 10:52 PM

I had been thinking about both of those capacitors. I'm mainly wondering what the specs I should be looking for, ESR, Impedance, Ripple and that kind of stuff. The 47uf Panasonic FC that I already have does a good job of reducing noises.

TheLaw117 26th May 2011 03:14 AM

I'm using 4x 4700uF 50V Nichicon GU. I'm still putting together the amp...but it is what the board I'm using recommended. The cost was $20. $5/cap. They are 105*C and some of the best ripple I could find at the price point. If I could find them in FM/FC, I would have. But it also would have been more expensive.

wintermute 26th May 2011 09:50 AM

Hi Einric, you only have 47uF per rail?? That's very low! You will almost certainly see an increase in your rail voltage going to 2200uF or more, and should be able to get more power at low frequencies (certainly in my case 20Hz sine wave power was better with 5700uF compared to 1000uF

FC's max out at 3900uF at 35V or 2200 if you need 50V, of course there is always the option to parallel. FM's max out at 1800uF at 35V.

Generally speaking, for a PS I believe low esr, high ripple and a high temp rating are good to have, the nichicons are only rated at 85deg


AndrewT 26th May 2011 10:01 AM

The decoupling caps supply almost all the transient current demand of the amplifier.
Put your best quality in as decoupling.
As you move away from the amplifier the intervening trace and cable impedances reduce the need for "speed" in the supply smoothing.
The large value decoupling on the amp PCB should probably be a high quality "Audio" type electrolytic.

Off board smoothing can be any reasonable quality electrolytic.
However, note that Peter does not use any off board smoothing. With his philosophy, it's all done with high Audio quality on board decoupling.

Peter and I are at opposite ends of the Spectrum on off board smoothing.

Einric 26th May 2011 01:31 PM

Correct, there is a 1500uf Panasonic FC onboard to the amplifier. I currently have a Radio Shack Special 2200uf Nichicon (Blue Whatever it is) per rail. I have been looking at some Elna Simlic II's; using two 1000uf's per rail or one 2200uf 100V Nichicon KG per rail.

I'm pushing +-35V into my LM4780 and I have it on a large (3"x5"x2") active heatsink. The heatsink barely gets warm to the touch after hours of playing at loud volumes. I will post some pictures soon.

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