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astrodog 27th June 2008 01:19 PM

Some basic questions.....
Hi everyone.....

I am starting to build an amp from the Silicon Chip kit using LM3876. So far I have built a power supply and one channel, all tests ok (no music yet though!). This will be run from the one 160VA 50V toroidal.

I am planning to begin with a separate power supply, mainly to aid with testing other imminent prototypes....

My question - With a separate PSU, should I have the toroidal and rectifier/filter circuits together, or should I put the rectifier/filters in with the amps, or does it not matter???

peranders 27th June 2008 01:24 PM

The voltage is max 2 x 28 VAC. I'll assume your transformer is 2 x 25 VAC?

You should always strive to have short wires between the "consumer" and the smoothing caps but why don't you have it together?

astrodog 27th June 2008 02:09 PM

Yes - transformer is 2x25 VAC.....

AndrewT 28th June 2008 02:00 PM

keep the transformer, rectifier and first stage smoothing very close together.
This will require a comparatively high value of decoupling capacitance to be located at the amplifier.

YFW 2nd July 2008 08:58 AM

You should put the rectifier/filters in with the amps, as near as possible to make the lengh short.To reduce the power supply impedance is very important for such amp.

AndrewT 2nd July 2008 09:18 AM


Originally posted by YFW
To reduce the power supply impedance is very important for such amp.
at mid and high frequencies is very important. That's why the decoupling must be located on the amp PCB.
The main smoothing is working at low frequency and some impedance inductance between smoothing and amplifier does little harm.

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