Hi all,

I wonder if anyone else is experiencing hum problems like described in this thread:

http://launch.groups.yahoo.com/group/Doepfer_a100/message/20598 threaded=1

I myself am constructing a A-100 system and recently reached the state were it can produce a sound, a MIDI2CV interface, one VCO and a VCA, as can be seen here: http://groups.yahoo.com/group/Doepfer_a100/photos/album/1838015066/pic/444387654/view picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc

The bus boards use the same power source but are not (yet) connected, hence the cable between the MIDI2CV interface and the VCO.

The power source is the one coming with the DIY kit #1 from Doepfer, suppling the AC current without a ground wire.

When I connect the VCA output to my Roland KC-110 amplifier, using a stereo mini-jack VCA out to the L/R Roland in channel, it starts to hum. The hum worsens when powering up the A-100.

I think I have to create some common power ground, as described by Florian Anwander in the before mentioned message:
The Doepfer system needs no additional ground, but it definitely
requires that all connected devices (A100 racks, external mixer,
poweramp, effects) share one common power ground. The power connector of all A-100 racks MUST be three prong connectors and the multi power
socket bar must use all three lines.

The ground from the mains however seems not to be propagated into the A-100. The Roland has its own power supply in the form of a mains to 13 V DC adapter.

How on God's green earth do I get a common power ground

All help & advice is appreciated!

Warm regards,

Ton Akveld