Trimming DC Offset on Nico's preamp - diyAudio
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Old 31st January 2013, 09:45 AM   #1
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Default Trimming DC Offset on Nico's preamp

I have assembled this preamp(link below) with the intention of capacitor-less coupling. One of the channels is having -6mV and the other shows -16mVdc approx. The complementary matching of these BD139-16 n BD140-16 from the twenty each I purchased was impossible and I want the offset to be as low as possible. Is there any changes in resistors/or addition of preset I can incorporate so that I can trim the offset.

Low Distortion High Dynamic Range Pre-amp

Help needed

Gajanan Phadte
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Old 31st January 2013, 10:00 AM   #2
lineup is offline lineup  Sweden
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6 and 16 mV is very good.
No need to have less DC-offset
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Old 31st January 2013, 11:56 AM   #3
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You can replace R5 or R6 with a trim pot.
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Old 1st February 2013, 03:20 AM   #4
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I tried to trim one of R3/R4, but I did not like the way it(DC offset) drifts.

My worry is that if I connect this directly to my power amp, it will have big DC at the output.

Gajanan Phadte

Last edited by gmphadte; 1st February 2013 at 03:20 AM. Reason: correction
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