Input wiring of Green Pre weirdess (now it's BLOWN = DEAD)

Should the INPUT XLR of the Green Pre pin 3 (ground) be grounded to the chassis or grounded to the circuit PCB???

i have it righ now to the PCB and as soon as I turn on the 48v switch i get a Ground Loop.

Never ground the Pin 3...wich is the cold.....
Only pin 1 to star ground.

Try both ways wich one works for you....ground pin 1 to pcb 0V or pin 1 and all pins 1 to star ground.

Thanks

thanks... i ment pin1 (not 3 )... will test it tonight.


when the preamp was without a box it was dead silent, and as I put it in the box it started HUMMING with the phantom.

I'd ground pin one to the chassis as soon as it enters the chassis ie have the shortest possible distance between pin 1 and the chassis. Then make this ground point the ground for the signal grounds star ground. Or ground the signal ground near the PSU's filter caps.

Ground the other inputs pin1's as soon as they enter the chassis, not at this star ground. You really don't want the noise that the xlr cables shielding picks up to get into your signal.

Remember that the 48v phantom powers current returns through the cables shielding. You do not want to ground it to the pcb. Ground it to the chassis as soon as possible.

Hope that helps. (sorry for saying 'ground' so much :grin: )
Rob

well i did measure some voltages:

taking away the 48V switch completly the two 6.8K resistors showed strange values:

Channel1: almoust 6V
Channel2: almouse 15V

when switching the phantom on it showed perfecto 48.1V.

but now that it isn't even connected why would i have voltage in the inputs?

now i'm pissed off.....

after some reading of voltages and stuff accidentally one cable touched a 220V part... switch blows... HOUSE FUSE blows too :shock: ...

checked everything: channel 1 dead.... channel 2 goods but strange...

i will kill this preamp and start all over again :twisted: