2. amps-preamps
  3. 991798550

HUM dilemma Can anyone solve This one?

Hi bob - read your posts on hum and hope you can help my dilemma. I have lexicon dc-1 preamp, krell kav250a, ead powermaster 500 and all b&w nautilus speakers. i have a continuous hum, as long as the amps are on. The preamp can be powered off, have satellite only, and if that wire is unscrewed from the wall, the hum is still there. Use a Monster HTS conditioner, all shielded interconnects, and everything is plugged into one outlet. Had three dimmers associated with the same circuit, and switched all of them for top-of-the line lutron dimmers (at $70/each!), switching every dimmer on the circuit. In fact, I ran everything by high grade extension cord to a different outlet on a different circuit - none of which changed a darn thing! The only thing that changes the tone of the hum is increasing or decreasing the degree of dimming on the dimmers - any of them. They are all grounded properly and have the latest RF suppression according to Lutron. The other difference I notice is that the speakers powered by the EAD Powermaster 500 tend to emit a slightly louder hum than the two mains attached to the krell. but when one listens, I still hear the hum in the mains as well. I will try cheater plugs, but dont want the expensive equipment at risk, but what else can i do? the last thing i should note is that i have six halogen bulbs in the dimmer switches, all of which hum similarly when dimmed. i am told this is acceptable, but the loudness of the dimmed bulbs is quite noticeable. Any ideas? This is a real dilemma for me! When sitting in the room with everything off (lights, preamp, tv, all lights, everything except the two amps [which are always powered on]), I still hear the hum! It's just audible enough that it makes sitting in what should be a quiet room kind of annoying. One last note - just to let you know I'm not crazy - even my girlfriend has noticed the hum and she doesn't know much about audio at all. She even jokes how her $200 system has less hum than my $25k system! Please help!!

In need,
Baz
bazmataz

Showing 1 response by sean

sean
6,231 posts
 
Try disconnecting ALL of your sources from your preamp. This means power cords and interconnects. See if this gets rid of the problem. If it does, add one source back at a time. First do the power cord into the wall and check that. Then connect the interconnects between the source and the preamp. EACH piece step BY step. This will tell you where the hum is coming in from IF it is source related.

If you disconnect the sources and it is still humming, try disconnecting one amp at a time. In other words, try the preamp and Krell and check results. Then try the preamp and EAD, etc.. If it does it with both amps, then just leave the amps plugged in with NO preamp connected. You've got to narrow it down as to where it is coming into the system and go from there.

I know that this can be VERY frustrating. I am currently in the same boat as you. I recently added a new DAC and i'm getting a VERY noticeable hum. While most of the reaction is between the DAC and preamp, i can plug the DAC directly into my amp and still hear the hum ever so slightly. Evidently, the DAC and that specific preamp just don't jive. Luckily, i have several of the same preamps, so i'm going to try swapping in a few others and see what happens. Who knows, i may have some leaky caps or ???

The weird thing is that changing power cords on the DAC makes a VERY noticeable difference in the pitch of the hum heard through the speakers. Who says that power cords don't make a difference ???? Sean
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