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DIY 250W/4ohm amplifier based on "blameless" topology, and measurements

OP
pma

pma

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Thread Starter #42
So the amp has been in operation about 2 months and it remains my main amplifier. I would like to share some construction details.

P1040402.JPG

In the middle is a delayed start board. It is absolutely necessary to have it because of the inrush current of the two 300W toroidal transformers. On left and right are PSU rectifier/filter boards.

P1040398.JPG

On left and right are output speaker protection boards with 90A MOSFET SSR circuits and opto isolation.

P1040399.JPG

Main amplifier board of one channel.
 

restorer-john

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#43
Thank you for sharing your build.

I think it's the first time I have seen a bridge rectifier made in India. A sign of things to come.

1620717403305.png
 
OP
pma

pma

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Thread Starter #44
Thank you for sharing your build.

I think it's the first time I have seen a bridge rectifier made in India. A sign of things to come.
Vishay, manufactured in India. About 10 years in operation in the same box, only with a different amplifier module (CFA). As you know, the "old world" has almost resigned to SS parts production.
 

restorer-john

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#45
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#46
Nice build!

The LF distortion comes from highly nonlinear ferrite choke 18mH. This is intentional and simulates the real speaker LF nonlinearity. Finite DF then makes rise of LF distortion
That's a good argument for bi-wiring actually: nonlinear woofer current * wire impedance creates distortion voltage at the speaker, which will be played back by the whole speaker, so if it's a 3 way the midrange driver will output this distortion voltage... With separate wires, distortion due to nonlinear woofer current will only be seen by the woofer.
 
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