CurtZHP
Well-known member
ruffrecords said:Yes
You test it with no audio. Short the input to minimise noise. You are just looking at the twice mains frequency ripply. It will be a lot higher than any noise created by the mic pre itself.
I don't risk my scope by connecting it directly to a big dc voltage with a small ac signal on it. I use a 100nF/400V cap from the HT supply to a 100K resistor the other side of which is connected to ground and measure across the 100K
Cheers
Ian
Moving right along! I added the additional decoupling you recommended using some parts I picked up this morning. Decided to just plug a mic in, throw on the headphones, and give it a listen.
The hum is GONE! Hallelujah!
Clean as a whistle.