IC's and Humm


I hooked up another amplifier that I added to my system. My preamp has two pair of outputs. Before my system is dead quiet. The new amplifier runs quiet as I tried it running my main speakers. But when I try it with a secondary small speakers I get humm....so I tried switching the IC's from my monoblocks(NBS) to this stereo amp which was connected using some ($100) Monster IC's. The NBS are dead quiet and the Monsters produce a low audible hum. When using the monsters the humm also increases slightly when I turn the lights on. I think the problem is that I have run out of dedicated ports for this amp....so I use a nearby regular port. Sorry for the long description but I'm wondering is it just the IC or should I have a couple more dedicated ports installed. I run 2 pairs of monoblocks,preamp,dac,transport....and to get it dead quiet is like a combination to a safe....it must have a certain layout or I get humm and my tube amps are realy finicky about it.
wavetrader
Another observation is that one VAC 140 will pickup humm if paired with another amp on the same port.

Perhaps, along the lines of what I was suggesting, that is because with the two amps each drawing substantial current from the same port, the voltage offset between that port and the port that the preamp is on is increased. Causing increased ac current flow in the shields of the interconnects between preamp and power amps. Again, your problem might be too many dedicated ports for the interconnected components, not too few.

Regards,
-- Al
If possible, try using balanced interconnects between your amp and preamp. I had a similar problem where my front speakers had no hum and my rear surrounds constantly had hum/buzz. Once I connected the xlr/balanced cables, the problem was completely eradicated.

Aaron
If possible, try using balanced interconnects between your amp and preamp.

Yes, if the cause of the problem is along the lines I described, a balanced interface (if your components support that) would most likely resolve it.

That is because with a balanced interface the power amp responds to the difference between the + and - signal inputs, and extraneous ground currents in the cable are ignored (unless they are so severe that they overwhelm the balanced operation, or what is more properly referred to as the common mode rejection capability).

If your components can't run balanced, again I would suggest that you try connecting everything, or at least preamp, power amps, and analog source components, to the same ac port. If that solves the problem, then see what you can move to separate ports without re-introducing the problem.

HTH,
-- Al
You may experience a "ground" differential problem using different AC circuits.It is also possible that this may arise from the quality of grounding in the two cables.Had you tried "floating" the earth-ground on the humming culprit?