Humming noise due to poss earthing problem with AV and 102

quote:

Originally posted by Beer Monster:
I currently feed the front outputs of the Marantz 4300 AV amp to the 102 and have noticed a considerable humming noise coming through the front speakers when selecting the AV. I know its the AV as when it is fully turned off, the hum subsides.
As the AV is not earthed (it only has a 2 pin plug) I have tried connecting the earth with the 102, but still no joy.....
Any ideas on how to get around this??

Does the 102 have a unity gain modification on the AV input??

Also try this:-

disconnect all sources from AV device, does hum dissapear?

if so, gradually plug in your sources until you find which source is the problem and go from there

What cable are you using to connect the AV amp to the 102? Is it phono-phono or phono-din?

When I first connected a Yamaha AV amp to a 202 with phono-phono I got mains hum caused by an earth loop somewhere. Changing to a Chord phono-din stopped the humming. Absolute silence, no earth loop.

I hope this helps.

Graham.

quote:

Originally posted by AV@naim:
disconnect all sources from AV device, does hum dissapear?

if so, gradually plug in your sources until you find which source is the problem and go from there

This is often the best diagnostic. When you plug in an AV amp or processor you often connect a SKY box, TV, VCR, communal aerial and Uncle Tom Cobbly and all. Any one (or several) of these may be the cause of your earth loop and perceived hum.

Be careful making and unmaking the connections - it is advised to have the units switched off when doing this. Connecting a device with a floating earth can (upon connection) do damage.

Thanks for your input, I know that if I turn off the AV completely, the hum disappears....
When I use the 102 via AV (via chord chrysalis phono to din), the volume control is set to 12 O'clock... can hear the hum, and when the AV is on standby, it is still there...

AV@Naim > What is the unity gain mod? I can I tell if it has one as I bought the 102 second hand?

quote:

AV@Naim > What is the unity gain mod? I can I tell if it has one as I bought the 102 second hand?

The unity gain mod effectivly bypasses the internal "variable" gain stages, allowing the AV processor to control the volume on that input, rather the pre-amp.

Unity gain manifests itself as fixed volume on a specific input (i.e. the volume control with do nothing when turned).

It sounds like you don't have the mod as you are able to adjust the volume, which probably means its something on the AV inputs causing problems.

BM

I am not against the official advice posted and I do agree with the systematic elimination of sources plugged in until the chain producing the hum is fully identified.

However the unity gain function is not a panacea for hum in my experience.

Yes it is convienient because volume control for the front channels then is at the master volume on the A/V kit along with the other channels AND you don't have to remember to turn down the volume on the 102 when switching to CD for example.
However it does not work to eliminate hum.

I have had a Denon A/V which had a floating earth which hummed away happily thru 'Unity gain' and a Sony A/v with a power line earth which did the same thing becasue buried in the TV/SAT connection are multiple potential hum loops which are difficult to eliminate.

regards
geoff