Sub B & W 610: hum problem

[GCE]

By attaching this sub to the secondary power outputs (spk B) of the amp I hear a great continuous "ummm", I think at 50 Hz, when the amp is switched off or when amp is on but with the spk B outputs turned off , to hear only spk A; hearing the music, with spk A and B togheter, all right; connecting sub with low-level input (signal) it's ok: is it normal, what can I do? Thank you!

 

[mpw]

if pm6004 has a pre-out.. use that for the sub and not the Speaker B terminals

Probably the signals coming to the sub from speaker B are at a higher signal level..if you have connected to the line in of the sub..

try connecting to the speaker in and check at low volume..

maybe more folks will chime in..

mpw

 

[GCE]

Pm 6004 has only rec 2 out, but with fixed vol output; if I connect a wire from amp's ground screw to one of the low level input shield of sub, the hum stops: but, is it safe? thanks.