Amp Hum/Noise

[zstoja]

Hello,

I have Kenwood KA-8150, about 85W RMS per channel.
If nothing plays, I can hear hum/noise from half power (-20db) to maximum (0db).

Is it normal or how much is it normal?

Thank you.

[E-Stat]

Hello,

I have Kenwood KA-8150, about 85W RMS per channel.
If nothing plays, I can hear hum/noise from half power (-20db) to maximum (0db).

Is it normal or how much is it normal?

First of all, power is logarithmic. It doubles (or halves as the case may be every 3db). A 10 db change is coincidentally a factor of 10. -20 db is 10 times 0.1 or one-hundredth. So you get hum from 0.85 watts to 85 watts. Doesn't sound normal even with a phono input which tend to be noisier.

Try isolating the cause by unhooking other source(s) you may have plugged in. A ground loop can be formed from another source like a tuner or TV. Check for loose or dirty connections. Check for signal wires crossed over or near power wires. Is the power outlet properly grounded?

Good luck!

rw

[risabet]

Hello,

I have Kenwood KA-8150, about 85W RMS per channel.
If nothing plays, I can hear hum/noise from half power (-20db) to maximum (0db).

Is it normal or how much is it normal?

Thank you.

Is this a receiver? Is this a 60hz hum or a higher hiss type noise?

Is this with a line level source i.e CD or a phono stage as the input, obvoiusly w/o music playing. If it is a phono input it may be normal for the unit. If it is a line level it should be very quiet if it is operating correctly. Do you have more than one 3-prong plug? Is so, try using a "cheater" plug to float the ground on all but one component. Did the noise go away? If it did you had a ground loop and you problem is solved. If not try below.

Unplug all of the input cables to the receiver? Did the hum/noise go away? If not than have the receiver? checked. Plug in one source unit at a time and listen. Does the hum return? With what unit? After all this it may be a bad IC or heaven knows what. One of the hardest things to find is the source of hum in complex systems. Good luck.

[zstoja]

First of all, thank you very much for details.

It is not receiver, just amplifier.

It seems I found reason for hum.
DVD is connected to VCR, VCR to Amp. If VCR is switched on (no playing), I got the hum. I know that it is not good way to connect units, but it is simple way.

Thank you, again.

[zstoja]

Just DVD/VCR is direct coonected to AUX.
If DVD/VCR is on (no playing), there is hiss (midrange and high), not 60Hz (it is very low).
If DVD/VCR is off, no hiss.
If I switch to phono (nothing is connected to phono), more hiss than with DVD/VCR on.
Tuner (nothing to tuner), no hiss.

Again, maybe this is normal?

[zstoja]

Unplug all of the input cables to the receiver? Did the hum/noise go away?

If all cables are unpluged, no hiss on AUX, just for Phono.

During playing nothing is wrong, I mean cannot hear it, too loud.