cafewalter
New member
- Joined
- Oct 10, 2014
- Messages
- 1
I'm fixing and calibrating a pair of dbx 165s. These are very old units: not 165A, no PeakStop, and they don't even have silk screening on the PCBs. These have black-can 202 VCAs. From parts codes I think they are from the very early 80s, but that's just a guess.
As I work through the calibration procedure, step 20 is a THD check. I am measuring rather higher distortion numbers than the instructions say I should. For instance, with 0dBu 1kHz at the input, no compression, and +20dBu output, the instructions say I should see < .05%, and instead I measure (with an Audio Precision analyzer) 0.27%, primarily third harmonic.
Were the calibration instructions just wishful thinking? Or, does the VCA distortion get worse with age (maybe the component values have drifted)? Is this something I should be trying to repair, or is it "part of the charm"?
As I work through the calibration procedure, step 20 is a THD check. I am measuring rather higher distortion numbers than the instructions say I should. For instance, with 0dBu 1kHz at the input, no compression, and +20dBu output, the instructions say I should see < .05%, and instead I measure (with an Audio Precision analyzer) 0.27%, primarily third harmonic.
Were the calibration instructions just wishful thinking? Or, does the VCA distortion get worse with age (maybe the component values have drifted)? Is this something I should be trying to repair, or is it "part of the charm"?
