2. amps-preamps
  3. 1232637880

Hissing and Hum through speakers

Hi everyone,
I have a fair amount of hissing and small hum coming through my speakers...when music is played at mid to high volumes the hissing and distortion is very audible through the tweeters/speakers. I don't think it is distortion (not sure how I can tell) I think it is that noise that exists in the system and it gets exaggerated at higher volumes...

I have a Panamax unit where everything is plugged in and the Panamax and amplifier plug in to the same wall outlet.

The noise goes away when I mute my pre-amp (Meridian 561.) But with the pre-amp on and non-muted and any source selected the noise is present. Even when the source is in pause.

Also, I have unplugged the inputs from the pre to the amp (line level) and the noise is still present. Same for my center channel amp, and I also have a third amp with same results..

Does this indicate that the noise is coming from my AC line? I have done most of the troubleshooting (different cables, plugging and unplugging sources, et cetera) that I know and have not been able to resolve...
yanniz
sarcher30
596 posts
 
Can you borrow a different preamp to see if its the preamp?

If one of your sources has a volume control or level attenuater you could bypass the preamp and see if that is the problem.

Another cause could be a ground loop. Try lifting the ground on the preamp with a cheater plug. If that doesnt work try it on the amps also. Some people recomend lifting all grounds. That may be an electrical shock hazard though.

Good luck
Sean
cyclonicman
693 posts
 
Do you have a Plasma/LCD TV also plugged into the outlet or on the same electrical line?
yanniz OP
6 posts
 
thanks for your responses..

I have moved the Plasma to another circuit. I do have a cable box in the rack, but plugging and unplugging the power of the box as well as the coaxial from the wall, made no difference.

I have tried a different preamp and I get the same results.

The preamp (Meridian 561) has a 3-prone cord and it is plugged in to the Panamax conditioner. So are the rest of the sources. The Panamax is plugged in to one plug on a duplex outlet and the Amplifier for the fronts is plugged in to the other plug of the same outlet.

Also, there possibly seems to be some level matching issues with the 561 (45 Ohms output impedance) and the amp (23.5K ohms input impedance on the rca inputs.) I tried to reduce the gain on the front L/R outputs of the 561 (via the software) from 0db to -2 db, and I think it made a slight difference with the hissing/distortion at high levels, not sure yet...

Not sure what it means exactly...I think if I keep reducing it more I will run out of gain (enough SPL) out of my amp soon, which is weird as it is suppose to be putting out 250W at 8 ohms (so around 330W with my 6 ohm speakers?)
More to discover