Page 1 of 1

dBx 303 A Schematic

PostPosted: Sun Feb 12, 2017 9:02 am
by mediatechnology
This is the dBx 303A schematic showing the discrete transistor Blackmer® VCA and RMS detector based on a CA3083 array.

Image
dBx 303A Schematic

Large format: http://www.proaudiodesignforum.com/imag ... Actual.jpg

Re: dBx 303 A Schematic

PostPosted: Fri Feb 17, 2017 10:56 am
by JR.
Old school logger... 1974 so early days.

JR

Re: dBx 303 A Schematic

PostPosted: Fri Feb 17, 2017 11:05 am
by mediatechnology
Someone may need to repair one.

Re: dBx 303 A Schematic

PostPosted: Fri Feb 17, 2017 11:41 am
by JR.
Back in the day I would devour schematics like this to learn circuit design. While I do not recall seeing these particular ones. I saw some similar tricks in Buff (Alice/Valley people) schematics. Not many designers were fluent in logging circuits (while the Nat Semi app notes did have generic designs to help sell their precision transistors (LM300?) for logging application.

Back in 1989 I got a patent for a variant class A VCA(US04818951 Roberts), this stuff by Blackmer was way ahead (Class AB) even back in the '70s, but that was before dbx/THAT corp decided to share technology.

JR