I agree with Ud, remove chassis and layout the modules in a string, Mains at one end, then through the stages, to the input RCA at the other end.
Couple up and power up.
Is hum or buzz heard and/or measured.
Connect as a stereo pair. Test again, measuring the hum or buzz.
Remove the source leaving the RCAs unterminated.
Does the noise measure worse?
Now that you know what the system can achieve, start casing it up.
Couple up and power up.
Is hum or buzz heard and/or measured.
Connect as a stereo pair. Test again, measuring the hum or buzz.
Remove the source leaving the RCAs unterminated.
Does the noise measure worse?
Now that you know what the system can achieve, start casing it up.
1) I have removed the rca from the chassis
2) Signal wire going to signal and grd wire going to ground
3) will check
4) will check
Thanks. Yes...wiggle the wires (that connects the rca and the board) and the buzz gets real loud....depending on how gentle or rough you wiggle them.
Will check again on solder.
do i need to connect the 'chg' from main board to the chassis? Did this and resolder the joints, now the buzz is less but when connect to preamp, the output from source (my radio for testing) is very faint.
"With dual mono version though, you will run a ground wire from CHG (chassis ground hook up point on each amp board) to chassis." post 168 from peter
now when i wiggle the rca wires....the buzz remains at same loudness. the buzzing sound is much lower now...but constant....sound from the radio is at background...can be heard when turn preamp volume to maximum.
Are you using dual mono or stereo setup? Do you have buzz with only a single channel connected to PS?
Is there buzzing when signal connected to one channel only (the other channel completely disconnected)?
If the buzzing can be detected with both channels connected separately, it's probably something else than bad soldering. It's quite unusual to get a hum with a single mono channel, unless the buzzing comes from your source?
dc offset at 14.5mv with volume down but when volume turn up to 9 o'clock....dc offset is at 7.9mv....and when turn all the way up, dc offset at 300mv!
Without input coupling cap it's normal for offset to change up to 80mV or so.
300mV high could indicate that your source produces some offset as well.
300mV high could indicate that your source produces some offset as well.
Stupid me....i forgot to turn the preamp source selector to tuner.....sorry everybody.....i feel very bad making you guys putting on your thinking cap to discover something i did stupid......now i got sound coming out from the speaker except the buzzing sound still exist...errrrrg...how the heck can i get rid of this buzz sound..it is very low and audible on close up......on both mono....same issue....how come? When i switch off the preamp, i still can hear this buzz from the speaker
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If your source is tuner it's quitepossible buzzing comes from it. Do you get hum with volume all way down?