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Accurate SC8000 schematic?

PostPosted: Wed Jan 21, 2015 8:01 pm
by BjornZetterlund
Hi everyone,

First post, so first of all thank you for a great forum. I recently got a 24ch and a 40ch Soundcraft 8000. According to the schematic available from the SC website, the 8000 house input module is meant to have an active panpot circuit (IC9). All my channels only go as high as IC8, the peak detect circuit...there is no active panpot circuit (IC9). Has anyone else found this to be the case? I have yet to do a complete trace of the circuit, but so far everything else seems to be accurate. Would be curious if other SC8000 owners have had the same experience?

Bjorn

Re: Accurate SC8000 schematic?

PostPosted: Thu Jan 22, 2015 1:01 am
by GJC Designs
The answer lies in the revision history notes in the top right corner of the ED2503 schematic:
Issue 1 6/11/86: released to production.
...
...
Issue 4 12/4/89: IC9 added.

Your console has PCBs that were made before the April 1989 update; there were a further 2 updates that followed shortly thereafter.

Revision history drawings have so far not been published. It is only the latest drawings that you will find on the website.

Re: Accurate SC8000 schematic?

PostPosted: Thu Jan 22, 2015 3:10 pm
by BjornZetterlund
Thank you very much for that, Gareth...I should have been able to figure that out for myself really.

Must say I'm a bit surprised to find an active panpot at all in this desk; usually an active or buffered pan will be used when the bus resistors are also lowered in value to take advantage of better noise and crosstalk. The 8000 doesn't do this, and presumably couldn't since the more basic input channel (pretty much identical to the 800B) doesn't have active pan and would therefore be unable to deal with lower bus impedance.

Seems to me that the only improvement the active pan brings on the 8000 would be the better pan law and the improved 'offness' (ie panning hard left removes nearly all the signal to the right). I was never aware either of those were big issues for a live desk, so it seems unusual to me that it was added. If you know anything about the history of the design of this desk I'd be very interested.

My favourite electronics book is Douglas Self's small signal audio design, it's been brilliant reading and offers so much insight into mixer design, and in particular with Soundcraft desks since I believe he was head of design there, and it says in your intro you worked with him. Must say it's brilliant to have you here being able to answer questions about Soundcraft desks, so thank you!

Bjorn

Re: Accurate SC8000 schematic?

PostPosted: Thu Jan 22, 2015 4:42 pm
by GJC Designs
Hi Bjorn,

Other than designing the first of the 8000 modules as adaptations of the 800B there was very little that I had to do with the 8000. I left Soundcraft in late 1986 before my work on the console was put into production. By the time I returned 2 years later, it was a well established product.

Doug's books are essential reading for pro audio :)

Cheers,

Re: Accurate SC8000 schematic?

PostPosted: Fri Jan 23, 2015 3:50 pm
by BjornZetterlund
Ok, thanks for your reply Gareth. Will get back to my 8000 mods...and Self reading!;)

Bjorn