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billy 26th December 2001 03:09 AM

Problems on ZEN amp
I finished the ZEN amp , but i find a little "hum" on the speaker , i isolate the transformer and using 2mH air core coil already and the total of supply capacitance is 40000uf which is same with the original circuit, but still has a "hum" problem. Any idea??

But the sound is very very good!! Thanks Mr.Pass.

richt 26th December 2001 06:58 AM


try repositioning the ground traces or replace with heavier wires!


Nelson Pass 26th December 2001 09:52 PM

Also, try the pi filter in the power supply as shown
in the "Zen Revisited" article.

By the way:

There is a slight flaw in the layout of the original PC
board. If you look at where R1 and C1 are joined on
each half of the board, you will note that the current
which charges C1 and C2 passes through the trace
between R1 and C1, and this creates a finite noise
voltage which shows up in the output.

This is easily fixed by attaching the + supply input
directly to the positive terminal of C1 on both sides
of the board.

And a tip of the hat to some DIYers in Europe who
noticed this error and pointed it out to me. :) This
helps, but I still recommend the pi filter also.

billy 28th December 2001 04:23 PM

stupid me, i still cannot soft the problem!! but i can accept it, because distance the speaker 1 feet about , i cannot hear it.

Thanks Mr.Pass & Richt

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