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In the Forum: Analog Playback
In the Thread: The last phonocorrector: “End of Life" Phonostage

Post Subject: More hamPosted by N-set on: 11/20/2011

I see the point, thanks a lot for your comments. Playing with the phono I've somehow come to a conlusion (possibly wrong)
that my ham is an electrostatic air pick-up from the PS. During the operation both PS and signal boxes are very close
together and the hum depends on the relative orientation of the two and gently fades away when switched off.
I must say though I have not done your trick with shorting the stages (only shorted the input) as it's difficult with this
design: 2nd stage is fixed bias, DC coupled to 3rd. I did pay a lot of attention to the ground, so actually cannot
imagine having a ground loop anywhere (I guess this is what you are referring to as improper grounding?).

However, if I lift the ground I get a horrible pick-up, which I think is in turn magnetic (it desappears instantly
when I switch the phono off). THis is actually something that worries me and perhaps indicates that
you may be right: why lifting the ground leads to such a drastic change?

Cheers,
N-set

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