dbx 128 - Circuitry Diagrams and Responses

B E F
+19 Overall Record Processing {Encode} Response Play Signal De-Emphasis
20 99 0 100 500° 1K SK 10K 20K
H
Combined Encode and Decode Response
2 aecono
Lever Marc
5K 10K 20K
Cc
Level Detector Bandpass Filter
D
5K 10K 20K
*dotted line - disc
solid line - tape
G. Overall Play Processing (Decode) Response H. Combined Encode and Decode Response
This is the single (swept) sine wave response of the decoding This is the combined effect of encoding and decoding, and
circuitry. Given a nominal level input at the dbx 128 input (a sine shows that the net result of dbx processing does not change the
wave signal swept across the audible spectrum), this is what the frequency content of the program. The only thing missing is the
dbx piay output will do. Note that the overall encode and decode noise and much of the distortion that would otherwise be intro-
response (curve H) is essentially flat, a combination of the PLAY duced as a result of the tape recording process. (Note: Play curve’s
and RECORD response (curve E plus curve G). vertical scale is corrected for the 1:2 expansion factor.)
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