Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => AmpTools/Tech Tips => Topic started by: Steve Blackdog on July 26, 2021, 12:04:46 pm

Title: Stethoscope hum
Post by: Steve Blackdog on July 26, 2021, 12:04:46 pm

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  :w2:

Cheers

Steve

Title: Re: Stethoscope hum
Post by: sluckey on July 26, 2021, 01:09:25 pm

Quote from: Steve Blackdog on July 26, 2021, 12:04:46 pm

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?

Title: Re: Stethoscope hum
Post by: Steve Blackdog on July 26, 2021, 05:28:54 pm

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