Stethoscope hum

[Steve Blackdog]

First, thanks Mr H for sharing your Amp Tools

I have just built a stethoscope and it works!  But is there meant to be so much hum when the hot probe is not touching anything?  It makes no discernible difference whether or not I use shielded cable 

Cheers

Steve

[sluckey]

I have just built a stethoscope and it works!  But is there meant to be so much hum when the hot probe is not touching anything?

That depends on how much gain your stethoscope amp has. Don't you have a gain pot on it?

[Steve Blackdog]

Yes, I do have a gain pot. I will have a play and see what difference it makes!