abechap024 said:
Wait I remember reading something in an original 160vu manual that the output circuitry is different and "noise sensing" or something and counter acts for noise is the line somehow (opamp feedback loop?) at the very least don't worry about it, but I am curious too how it exactly works, must be pretty simple. I see if I can dig of that manual.
Since I wonder, too (Even though I do not build the unit, or own it, only the humble dbx 117, which I like a lot), I had a look at the manual and the schematics.
The manual states hum suppression with that circuit and the way I see how it could work, I might be wrong though, is:
R92, R83, R84 and R33 are all 1% resistors, the first two are going to pin3, the latter building the feedback network. So, if any hum gets into the compressor through the output, it will be the same amplitude on pin2 and 3. On Pin2 it will travel the feedback network to the negative input of the 301 the same amount of hum should enter the positive input of the 301 through R92. It will be canceled at the ouput of the opamp.
R93 and R103 are obviously simulating the output impedance at pin2, so you have an impedance balanced output and also the noise entering through Pin2 and 3 sees the same impedance on both lines.
So DBX did not rely on the following device (It might be unbalanced anyway) to cancel any noise, but built a circuit do do it in the 160 itself. Seems clever to me.
