you are looking for <10.0mVdc as output offset.
Using a scale with a resolution of 10mV (0.01Vdc) can leave you seeing a 10mV, or even 20mV, reading that you cannot rely on.
The least significant figure has a lot of variation. The meter spec should tell you how reliable/unreliable that last digit is.
Using a scale with a resolution of 10mV (0.01Vdc) can leave you seeing a 10mV, or even 20mV, reading that you cannot rely on.
The least significant figure has a lot of variation. The meter spec should tell you how reliable/unreliable that last digit is.
Hi, tauro
I cant remember exactly why, its 6 years ago I built it. Probably because I was a poor minimalist. But think that's the way the original gainclone was built and how the lm3875 kits from audiosector.com are built.
I do want to install some caps, maybe 2x 6800uF and probably bypass them. Just dont have a lot of cash now either and the shipping is expensive. Was thinking if gutting an old broken amp if I can find one.
The caps on the amp boards are 2x 1500uF bypassed with 01.uF, but would like to try the caps recommended by tomchr on the forum.
Might not be be optimal without the caps, but seems to work well enough for audiosector.
I cant remember exactly why, its 6 years ago I built it. Probably because I was a poor minimalist. But think that's the way the original gainclone was built and how the lm3875 kits from audiosector.com are built.
I do want to install some caps, maybe 2x 6800uF and probably bypass them. Just dont have a lot of cash now either and the shipping is expensive. Was thinking if gutting an old broken amp if I can find one.
The caps on the amp boards are 2x 1500uF bypassed with 01.uF, but would like to try the caps recommended by tomchr on the forum.
Might not be be optimal without the caps, but seems to work well enough for audiosector.
Minor treble channel hum solved
A minor hum was found on treble channels (high sensitivity driver plus horn) of a Hauptwork installation. Plate style amps and speakers are some 50 feet from the 4 channel preamp. The residual hum was a ground loop. Lifting the amp safety ground stopped the hum, but this is not safe. A solution was to put a pair of paralleled small power diodes (back to back) in series with box safety ground lead. For fractional millivolt signals the ground loop is broken. For a system fault, the voltage will be over the 0.6 v level and the diodes will conduct. JSR.
A minor hum was found on treble channels (high sensitivity driver plus horn) of a Hauptwork installation. Plate style amps and speakers are some 50 feet from the 4 channel preamp. The residual hum was a ground loop. Lifting the amp safety ground stopped the hum, but this is not safe. A solution was to put a pair of paralleled small power diodes (back to back) in series with box safety ground lead. For fractional millivolt signals the ground loop is broken. For a system fault, the voltage will be over the 0.6 v level and the diodes will conduct. JSR.
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