[boycephoto]

I moved my small system to the bedroom and found a hum problem with my Insight+ EC.    The system is as follows,
Insight+ EC
Ultimate 70
Fet Valve DAC
Marantz SA8260 SACD, CD transport
Velodyne MiniVee
all AC is switched through an Adcom ACE 515 AC filter
and Rogers LS3/5a speakers.

I normally don't need to use the tone controls on the EC.  Tonight I was listening to Copeland and the highs were just to bright, I used the tone control and turned down the treble... sounded better, great.  When turning off the system I turned to volume down, and when I touched to treble control to return it to the center position the left speaker produced an audible hum.  Releasing my touch the hum went away, touching again created the hum, when I touched the bass control I heard a lower frequency hum at a lower level.  When I switched to tone controls out the hum diminished but did not totally go away.  This only happens with the tone controls, all others controls are totally quiet when touched.   I don't listen with my thumb on the treble so it is not a listening problem but, it doesn't seem like this should happen. 

Any ideas? 

[Wayner]

This is normal on AVA EC preamps. To keep circuits simple as possible and to have the least amount of other "bad" side effects, this was the acceptable side effect. Hopefully, you won't be listening to music while operating the tone controls.

Wayner

[boycephoto]

Thanks for the update, hardly ever using the tone controls this was a new phenomena to me.   

Dave

[avahifi]

This is an issue with the tone control pots themselves.  The only ones we could find with all other useful specifications do not have grounded shafts.  Thus it is possible to induce a bit of electostatic noise into the system by touching them, depending up the humidity in your room.  All of our other controls do have grounded shafts eliminating this effect.  It is only a minor issue while actually touching the bass or treble controls, they will be quiet in normal listening use.

The only cure would be to use plastic insulated knobs, and that would be pretty ugly. Or you could put on rubber gloves when operating these controls. 

Frank Van Alstine

[rcag_ils]

The only ones we could find with all other useful specifications do not have grounded shafts.

What spec. that ungrounded shaft pots have that the grounded ones don't other than the grounded shaft cost more?

Aren't they all potentiometers that varies resistance?