903-51X Comp / Limit

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[silent:arts]

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Documents:

903-51X schematic
903-51X PCBs
903-51X Parts List
calibration procedure

Full Kits are available in the White Market
 

tzman

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Awesome!
Nice to see how you managed to shrink the size! Ow, and are we seeing a little teaser in the background?
 

[silent:arts]

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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 ...
 

[silent:arts]

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Patrick from Davis said:
I see you picked sonically superior yellow for the PCB's.  Good call.
Patrick, my PCBs are color coded. Yellow needs +/-24V ;-)

tzman said:
Ow, and are we seeing a little teaser in the background?
No. Just my eight slot Backplane with SubD25 only.
 

tzman

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[silent:arts] said:
Anybody knows how to calibrate the 903 correctly?
Can't find anything. However, we will find out ...

I think you can get a lot from the 160X service manual in the Tech Docs section...
 

mitsos

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Cool! What's the second pushbutton?  Overeasy toggle?  Can you elaborate on what features you guys are adding?  Very curious!
 

gyraf

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GREAT idea making the DBX903 for 51X-format!

What do you use for the obscure RMS-converter chip?

Jakob E.
 

[silent:arts]

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mitsos said:
Cool! What's the second pushbutton?  Overeasy toggle?  Can you elaborate on what features you guys are adding?  Very curious!
the 2nd pushbutton is for stereo link. not tested yet. just summes up the CV signals.
further features are the choice of unbalanced output (original), impedance balanced output or transformer balanced output.


gyraf said:
What do you use for the obscure RMS-converter chip?
the same dbx used on a daughter PCB: 1 x CA3083, 1 x BC550, 1 x 1N4148 (see attached pic)
 

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gyraf

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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.
 

culteousness1

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Would be great to replace the obsolete CA30823 in the emulation circuit as well  :eek:
THAT300 series only features 4 NPNs in an array. Don't know of any other array of 5 elements though...
 

[silent:arts]

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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.
 

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Bassniac

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Hey

When do you start to sell them? I will be one of you first customers. Then I can finally get rid of my 160A.

Cheers.
 

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