"Jay" wrote in message
om...
I am trying to find a way to record telephone conversations to my PC,
(legal, for training purposes only). I have an interface that plugs
into a cassette recorder and that works fine on the cassette. I have
tried this same interface plugged into my computer, either line-in or
the microphone jack, but when I record I get a loud hum noise and I
can faintly hear myself in the background, though I have to talk or
whistle loudly to do so. Apparantly I need a different interface. I
have found them for sale for around $50, but I would prefer to make my
on, usually these interfaces use fairly simply filter circuits. Any
suggestions?

Thanks

I suspect the problem is a grounding one. If you plug into the microphone
input of your cassette recorder and all works well and then move the plug
over to your computer mic input and all you get is hum, then check to see if
your 'interface' is powered. If it is, use an isolation transformer or
temporarily run it by battery. If it then works, you can sole the problem
permanently.