![[silent:arts]](https://cdn.imagearchive.com/groupdiy/data/avatars/m/0/172.jpg?1620371656){kind=avatar}
[silent:arts]
Well-known member
Documents:
903-51X schematic
903-51X PCBs
903-51X Parts List
calibration procedure
Full Kits are available in the White Market
903-51X Comp / Limit
- Thread starter [silent:arts]
- Start date
Help Support GroupDIY Audio Forum:
Documents:
903-51X schematic
903-51X PCBs
903-51X Parts List
calibration procedure
Full Kits are available in the White Market
[silent:arts]
Well-known member
bernbrue
Well-known member
8)
Bernd
Bernd
culteousness1
Well-known member
Ah, the prototype PCBs have arrived! Nice, Volker!
Patrick from Davis
Well-known member
I see you picked sonically superior yellow for the PCB's. Good call.
Patrick
Patrick
tzman
Well-known member
Awesome!
Nice to see how you managed to shrink the size! Ow, and are we seeing a little teaser in the background?
Nice to see how you managed to shrink the size! Ow, and are we seeing a little teaser in the background?
[silent:arts]
Well-known member
First test (without VCA, just with a jumper wire): passes audio fine, +21,5dB gain.
Without (VCA and) any calibration 0,004% THD in the audio path. Cool.
Anybody knows how to calibrate the 903 correctly?
Can't find anything. However, we will find out ...
Without (VCA and) any calibration 0,004% THD in the audio path. Cool.
Anybody knows how to calibrate the 903 correctly?
Can't find anything. However, we will find out ...
[silent:arts]
Well-known member
Patrick, my PCBs are color coded. Yellow needs +/-24V ;-)Patrick from Davis said:
No. Just my eight slot Backplane with SubD25 only.tzman said:
tzman
Well-known member
[silent:arts] said:
I think you can get a lot from the 160X service manual in the Tech Docs section...
usekgb
Well-known member
I was thinking about taking this on at some point. I'm glad to see it's in good hands!
peterc
Well-known member
Very nice! Love the dbx stuff.
Peter
Peter
GREAT idea making the DBX903 for 51X-format!
What do you use for the obscure RMS-converter chip?
Jakob E.
What do you use for the obscure RMS-converter chip?
Jakob E.
[silent:arts]
Well-known member
the 2nd pushbutton is for stereo link. not tested yet. just summes up the CV signals.mitsos said:
further features are the choice of unbalanced output (original), impedance balanced output or transformer balanced output.
the same dbx used on a daughter PCB: 1 x CA3083, 1 x BC550, 1 x 1N4148 (see attached pic)gyraf said:
Attachments
Nice! I've only seen 903's with DBX's own obscure semi-pro RMS chip - that sub circuit makes a lot of sense!
Jakob E.
Jakob E.
culteousness1
Well-known member
Would be great to replace the obsolete CA30823 in the emulation circuit as well 
THAT300 series only features 4 NPNs in an array. Don't know of any other array of 5 elements though...
THAT300 series only features 4 NPNs in an array. Don't know of any other array of 5 elements though...
[silent:arts]
Well-known member
CA3083 are no problem, I can still get them way cheaper than any THAT array.
Looking at the THAT 2252 and THATs product politics I'm not sure how long the arrays will be available ...
Jakob, attached a foto of the dbx replacement. Never have seen any without, and even found some PCB overlays for the 902 with the substitute PCB drawn on top of the 146221.
However, looks like there have been many different revisions, even with 1252 and 1253 ICs.
Looking at the THAT 2252 and THATs product politics I'm not sure how long the arrays will be available ...
Jakob, attached a foto of the dbx replacement. Never have seen any without, and even found some PCB overlays for the 902 with the substitute PCB drawn on top of the 146221.
However, looks like there have been many different revisions, even with 1252 and 1253 ICs.
Attachments
[silent:arts]
Well-known member
First it must be up and running and completely testedBassniac said:
