Hi All,
Hope I have found the right community for this!
I am trying to eliminate the source of hum in my home studio and it refuses to go.
I have stripped the equipment back to basics and slowly built it back up. All the mains plugs for each unit go back to the same single outlet in a star earth congig ( I'm UK. 240 volt 50Hz). All balanced to unbalanced have had the cold/ring/pin 3 wired to the screen at the unbalanced end (as the A&H is unbalanced)
this is the order:
1. Allen & Heath GS3 console + Genelec 1030 - All fine at full control room volume
2 MOTU 828 mk1 added, slight hum but not annoying
3. Behringer ADA8000 converter added,bigger hum when all faders set to unity, but turn down one set or the other ( ie leave 828 up and 8000 down, vice versa) the hum is enormous. Both appear to have good earths on the mains. it alsmost seems as if the hum goes out of phase and cancels when they are at the same level. I have checked the signal phase ( to check I had not revesed the wiring) by playing identical sound files through both and it seems to be fine in that regard.
I cannot see how I can do anything else with these. If I turn off the ADA8000 the hum diminishes, but disappears from the console altogether if I disconnect its mains plug ( whilst the 828 is still up in the mix). The ADA 8000 is totally silent when the MOTU 828 is off.
The transformer in the MOTU 828 is quite audible acoustically from the unit itself and sounds to be at the same pitch, Could this be the culprit?
any help would be appreciated.
thanks
Barkley