Another Hum Problem Question

Vantageaudio,
Good article suggestion. Thanks!

Claud,

I had a similar problem recently and appreciate the frustration. Sent my Proceed AVP into Madrigal (for the 3rd time) to fix a DAC problem and light problem. When it came back I had a very disturbing hiss. Had already fixed ground loop from cable TV problem months ago. I didn't want to send AVP back to Madrigal since they take forever, so I spoke with the Proceed tech and had them send a new DAC board since that was the major change. Turns out Madrigal FORGOT to put a screw into the inner board that grounds the AVP!! As soon as a screw was put in the hiss was gone. I have never heard of this happening to anyone else. After spending 3 weeks trying to figure out what it was, I never would have found it without taking the thing apart. Hope this helps.

JJ

There is a bad joke that goes around; that the best way to stop your amp from humming is to teach it the words!!

Yo Claud,
I suspect your hum is caused by the new interconnects. You mentioned that "If nothing is connected to my amp, it's quiet when every thing else is cut off. If I connect the balanced ICs I get a low volume hum through the speakers."
Since you didn't mention what they are, how long they are, or if they are running near any power cords, then we'll go through the whole list.

First, are they shielded? If not try replacing them with ones that are known to be shielded.

Second, are they longer than a meter? If so, is there any way to reduce the distance between pre-amp and power amp and use shorter ones?

Third, are they running next to any power cords, wall outlets, amplifiers, subwoofers, tv sets, flourescent light fixtures or any other device that has a magnetic field around it? If so, can you move the interconnects to achieve more distance from the magnetic field?

Progessive Electronics make a tool for the telephone installers called a 200B Inductive Amplifier; it's about $35.00. It has a magnetic pick-up at one end and when placed next to a wire with an AC signal or current flowing through it, the 200B will allow you to hear the signal (or hum if it's AC power). With it you can find the source of your hum very quickly.

Hum problem solved. Preamp drops it's ground as part of it's protective circuit when it's cut off. Company pres said to leave it on 24/7. Tubes will last about four years.I didn't call him, he called me because I had talked with his support person about this and other hums .Amp and pre are both on--dead silence. Merry Christmas guys and thanks for your help.
claud