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added amp...now hiss from spkr's

Addd an amp to the mix. SS multi-ch. Had no problems prior in relatively simple rig or atleast I did not notice. After making connections to recv'r(now used as pre/pro) I noticed a slight hiss/static like sound comimg from mids on my spkr's. So the process of elimination/isolation began. Long story short, I narrowed it down to the hiss/buzz coming from spkr's with only the amp connected. Nothing else...no interconnects no nothing. That cancels out cable problems, bad dvd player, etc, etc. Just power cable plugged in and wires going from amp to spkrs. When powered on it makes the noise. Amp runs quiet as far as I can tell when putting ear next to it. What's the deal? Tried diff outlets, diff spkr...makes no difference. When taking amp out of the mix and connecting spkr's to recvr, there is no noise at idle. Amp plays fine/sounds fine but the noise, although slight, is bugging me to pieces. Amp was shipped to me and had shifted cady/catty corner while in it's factory packaging which is pretty substantial. Perhaps it took a hit/drop...weighs about 80 lbs! Could something have gotten jared loose...a transformer which it has two of and quite large. Or is it the nature of the beast to output some noise when at idle? Thank you.
mnnc
freemand
225 posts
 
Mnnc,

What amp is it?
eldartford
4,262 posts
 
"Hiss" and "static" have nothing to do with AC power cords and the like, which can cause hum. You are probably hearing a characteristic of the amp electronics. Since all channels of this multichannel amp have the problem it probably means that there is no fault. It is only recently that we got amps which are dead quiet. In the good old days all amps made a little noise...that's how you knew they were turned on. The only thing I can think of which you might try is to short the input to one channel and see if it gets less noisy. If so it suggests that a preamp with low output impedance might help.
tiffany
8 posts
 
I think most homes do have 15 amps and it's a good idea for you to upgrade yours...but I don't think that's why you're having the hum issue. I have a mixer/amp that hums loud and I managed to minimize that dramatically by just using the "cheater" plug. My Cary Rocket 88R is dead quiet despite cables overlapping and touching everywhere! My Cary V12i's mono blocs are the ones that hum and with my set up, it's impossible to keep the cables separated. I would have to sell all my cables and buy new lengths to accomplish that.

I will try to get my hands on a humbuster and let you know if it really works. In the meantime, we may have to just take many others' advice that it's "the nature of the beast" and overlook it as long as you don't hear the hum from your chair. With having said that, the room is soooo much quieter once I shut off the amps :( :( :( However, the music is still sublime :)

And if you haven't done so, try the cheater plug on your amp.
mnnc OP
175 posts
 
How do I short input to one ch? Would you explain process please...thanks.
eldartford
4,262 posts
 
Mnnc...One way would be to plug in an interconnect, and then, at the other end, short the center pin to the body of the rca connector. "Short" means touch something metal (like a screwdriver) to both parts.

By the way I notice that you are using a receiver as a preamp. I assume that the receiver has connections for "pre out" and "amp in" that are normally jumpered. This probably means your signal into the new amp is not low impedance as from a dedicated preamp.
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