ferrochrome
Well-known member
- Joined
- Oct 3, 2011
- Messages
- 60
I built two stereo linked 1176 revD compressors into a 2u case some while ago and after finally starting to use it in my studio I'm experiencing a massive hum from both channels. Its there with the output potensiometer turned ccw, but it gradually increases when turning output cw. Same on both channels.
It's a low freq hum, typical transformer hum. My voltages are OK, and the compressors work flawlessly otherwise, stereolinked as well as dual. So I'm suspecting ground loops. I'm using the mnats "little psu", and when I built it I thought my grounding was as spesified according to the manual.
Has anyone built a similar stereo 1176 without hum? I'll post a description of my 2-1176's grounding soon!
Picture shows the unit while trying to troubleshoot. Both stereolink boards groundings detached (by the output transformer mounting screws), and also one detached ground wire from the left hand 1176 board. right board grounded to AC ground point. I've been trying attaching only one board to ground, different grounding points. Also I tried lifting both output pins1 to ground. Nothing helps so far..
EDIT: Solved the hum problem (was comming from psu) by lowering the 30V rail voltage, in my case down to 28V. The regulator (LM317) doesn't function properly when adjusting less than 3V. Check thread for alternative regulator!
It's a low freq hum, typical transformer hum. My voltages are OK, and the compressors work flawlessly otherwise, stereolinked as well as dual. So I'm suspecting ground loops. I'm using the mnats "little psu", and when I built it I thought my grounding was as spesified according to the manual.
Has anyone built a similar stereo 1176 without hum? I'll post a description of my 2-1176's grounding soon!
Picture shows the unit while trying to troubleshoot. Both stereolink boards groundings detached (by the output transformer mounting screws), and also one detached ground wire from the left hand 1176 board. right board grounded to AC ground point. I've been trying attaching only one board to ground, different grounding points. Also I tried lifting both output pins1 to ground. Nothing helps so far..
EDIT: Solved the hum problem (was comming from psu) by lowering the 30V rail voltage, in my case down to 28V. The regulator (LM317) doesn't function properly when adjusting less than 3V. Check thread for alternative regulator!