2. amps-preamps
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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
glen's avatar
glen
714 posts
 
Mixing lighting and plugs on the same circuit is an industry no no.(Electrical construction) Who ever wired your house was not very bright. You may have a grounding problem at the panel itself. Or somewhere in the circuit. An unbalanced neutral or a neutral balanced on two hots can have an adverse effect. (This is a common practice in house wiring) Ballests in light fixtures create a lot of noise in circuits if applicable. A cheater plug defeats the ground completly. If there is ever a short to metal on your unit guess who becomes the ground wire. Think of your ground as a life jacket and never take it off. A good start is a dedicated circuit or two each with a dedicated neutral and isolated ground attached to an IG recptacle.
Glen
bazmataz OP
43 posts
 
Hmmm.. Some responses make me wonder if everyone has read what I wrote above. I moved everything to a dedicated circuit by a high grade extension cord to a different outlet, on a different circuit, one without dimmers or even light switches! The tone/hum stayed exactly the same. That is why this dilemma is so confusing. There doesn't seem to be a common denominator anywhere... that is why i believe adding an isolated circuit will make this problem go away... any other ideas???? Thanks! Baz
xframe
1 posts
 
There are those who believe that only the plug that connects to the wall outlet has to be grounded to provide protection for your circuitry. Use of multiple 3-pronged connecters into your conditoner or other intermediary components increases the chance of ground loop propagation.

Please refer to Michael Elliot's (Owner and designer of Counterpoint, now Altavistaaudio, electronics) recommendation:
http://www.altavistaaudio.com/hum.html

Please note that Mike beleives that if yoru problem is a ground loop issue no matter how expensive your line conditioner is it won't eliminate it.
I hope this help your situation.

I had two sources of hums in my system: one turned out to be inside the amp itself (xformer was oriented horizontally facing the audio circuits and emitted electronic picked up by the audio circuitry). This was fixed by the manufacturer.
The second source was ground loop also modulated by a dimmer controlled lights. Reducing the number of 3-pronged connectors eliminated 90 % of the hum but I still have a very minor hum.

keith
bob_bundus
1,834 posts
 
Baz I replied privately to your email inquiry, but it came back twice as "undeliverable". I then sent the same reply thru Audiogon emailer; of couse I dunno if it was received. If not then give me an email address that works OK?
bazmataz OP
43 posts
 
Thanks bob. I'll check e-mail and try your suggestions. As for the other suggestions, nothing has quite helped yet. I'll let you know when I have time to disconnect the sources to the preamp and disconnect all the inputs to the amps and check it again. Thanks! -Baz
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