Strange noise...?

[Skorpio]

I have build a pre-amplifier and it is very quiet, no hum or noise even with my ears close to the speakers.....but...

When I touch the volume control a buzzing sound comes in both speakers....and only when volume is turned up.....not in minimum.....

It is not very loud, but it puzzels me and is a little annoing.....

[jaycee]

This is the 50hz field of power being picked up by your body and injected into the preamps inputs.

Is your case grounded to mains safety ground? If not, you should do this. If it is, you should have your house wiring checked in case you have a bad safety ground connection

Does the input stage of your preamp circuit include filtering?

[Skorpio]

The baseplate is grounded but the front is not.....

There is no filtering on inputs.....

[fotios]

Originally posted by Skorpio
I have build a pre-amplifier and it is very quiet, no hum or noise even with my ears close to the speakers.....but...

When I touch the volume control a buzzing sound comes in both speakers....and only when volume is turned up.....not in minimum.....

It is not very loud, but it puzzels me and is a little annoing.....

Have you checked if this noise heared also if you touch any other place on the metal case? Tell me this.
Fotios

[Jan Dupont]

jaycee;
For your information, we do not have safety earth in our normal wall plugs here in Denmark

Skorpio;
What type of volume pot are you using ?
Have you tried to connect the pot/face plate to PSU Gnd ?

[jaycee]

Originally posted by ACD
jaycee;
For your information, we do not have safety earth in our normal wall plugs here in Denmark

[Jan Dupont]

jaycee;
Thats right
Reel men doesn't take back-up or uses safety earth

We have safety earth for household machines like wasing machines, dish washers etc., but not in our standard wall plug for lamps, TV and audio etc....

[Jan Dupont]

However....
Can't count the many times I have been exposed to 230VAC
Maybe thats why my brain works like it does

[AndrewT]

it's about time we did the humanitarian thing and moved the whole population out of Denmark.

The rules are very different here.
We have to ensure that all exposed conductive parts are connected to safety earth.
If you at least connect all the exposed conductive parts to audio ground then some measure of interference attenuation will accrue.
The metal case around the pot is probably electrically connected to the adjusting knob and to the front panel. Earthing the panel AND the pot case AND the adjusting knob will probably solve the problem.

The pot track and it's three/six terminals should be isolated from the pot casing.

BTW,
how do you make a 220Vac system safe to the user if there is normally no safety earth?

[Jan Dupont]

BTW,
how do you make a 220Vac system safe to the user if there is normally no safety earth?

We don't... We are suposed to be wise people, that make our electric connection correct, so no safety earht are needed....

Or maybe it's a way to keep the population growh down