Problem with PI PSU

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My Aleph monoblocks are using 2 times 33,000 microfarads for a total of 66,000 microfarads of capacitance for each rail. At full load (3amps per side, 6amps total bias) the ripple on the caps were at 63millivolts. I found some 12 gauge .56 millihenries chokes at a surplus store for a dollar so I thought I would give them a try. With these installed between the caps for a test, the ripple went down to 10 to 11 millivolts. Thats a reduction of about 16db.

I'm in the process of completing my project and have'nt listened to hear if I need them. The measurements were made with resistive loads to test the results. I put two of these chokes in series and the ripple went down to, guess what, half, 5 millivolts. I have left provisions to install them if the noise is objectionable.

Hello AlexMark,

You can use the power supply like shown on the enclosed circuit.
It is possible to drive two channels with the one power supply, but if you can, try to use one per each channel.


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Wouldn't it be better to have more capacitance after the inductors? Seems to me that having a smaller amount of capacitance followed by the coils to provide "smoothing" then following that with a few nice big cans (or maybe better yet lots of small ones) would be ideal, but the schematic shown shows more capacitance before the coils. Is my thinking backwards?
Joined 2002


I don't have the power supply PCB of the Aleph 5 amplifier.
The circuit is very simple and it can be builted without the PCB.
I tried the above circuit, one per channel, with air core coils and without PCB, and there is no any kind of hum, even when you put your ear on the speaker.
Also, you can use the one supply for two channels, but it is much better if you use one per each channel.
Only thing that you must watch out, is the gaugue of the Cu wire on coils, like also Mr.Pass said.

Best regards,
Kristijan Kljucaric
you don't even have to use coils

If coils are not available a 10 Watt 0.22 ohm resistor works pretty
well with a large capacitance supply. It is not just the 120 Hz conponents that are worth reducing. The ripple voltage contains many higher frequency components as well that even an RC filter can significantly reduce.

diyAudio Editor
Joined 2001
Paid Member
Wiki Scmicky

The resistor has been periferally mentioned before, but I don't think very well explained (OK , because it is so simple)

The resister is in series in the circuit? ie all the amps run through it? perhaps you should mention how many amps this 10 watter can take. I understand that it is low resistance, so can handle a lot of current.

Is it best between the caps or on one end or the other?
Does it do any screwy stuff with the volts depending on location like the coils? (I doubt it, but best to conider every option!)

I finallly looked at the Wiki yesterday and I would like to set up a secton about the power supply issues that have come up again here. As some of you know, the power supply is what gave me the most problems while making the supply for my S of Zen.

I am also pretty ignorant, but I can cut and paste all of these references into it and massage them into a coherent structure.

Then you heavy hitters can come along and tweak it here or there, and viola-no more power supply questions hahahahahaahahahahahahahaahhaahhhh.

Well it's worth a try.

So, I need a suggestion on what to call my contribution and what catagory to put it in? I guess "power supplies" in "solid state"
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