dbx 165 distortion spec
« on: August 07, 2019, 02:26:02 PM »
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"?


Related Topics

  Subject / Started by Replies Last post
4 Replies
Last post April 05, 2005, 02:44:25 PM
by tubemonkey35
4 Replies
Last post September 01, 2012, 08:18:03 PM
by plumsolly
39 Replies
Last post June 30, 2009, 01:39:21 PM
by kb
2 Replies
Last post February 13, 2011, 06:44:16 PM
by plumsolly