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Pre amps rack/ summing box

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Pre amps rack/ summing box

Postby JPHogg » Thu Jan 24, 2013 12:51 pm

I have an 8ch soundcraft series 200b mixer. My idea was to chop it up and make a rack with just the pre-amps and eq with insert points and output post eq.
I was wondering if I could combine this with a summing mixer by adding a pot on each channel and a button to route to the L/R instead of the Direct Output.

I don't know much about electronics but have someone who can do the work no problem.
Just after thoughts on whether this will work and any tips on proceeding.

Cheers
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Re: Pre amps rack/ summing box

Postby ef37a » Thu Jan 24, 2013 1:39 pm

JPHogg wrote:I have an 8ch soundcraft series 200b mixer. My idea was to chop it up and make a rack with just the pre-amps and eq with insert points and output post eq.
I was wondering if I could combine this with a summing mixer by adding a pot on each channel and a button to route to the L/R instead of the Direct Output.

I don't know much about electronics but have someone who can do the work no problem.
Just after thoughts on whether this will work and any tips on proceeding.

Cheers
I would strongly advise against it. Heck of a lot of work and expense.A decent rack enclosure will set you back 50quid + for starters. Then, building a "mixer" is not a trivial excercise, ground loops, instabilities, clicks, plops and tweets will all need to be ironed out.

Unless this guy is going to work long and hard for nothing, sell the Soundcraft and buy a rack mixer, even the delicious Neve reviewed here some time ago is in the ball park of what I would charge you to build what you want!

This looks ok...http://www.rolls.com/product.php?pid=RM82 You can research a price!

Dave.
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Re: Pre amps rack/ summing box

Postby Hugh Robjohns » Thu Jan 24, 2013 3:57 pm

JPHogg wrote:I have an 8ch soundcraft series 200b mixer. My idea was to chop it up and make a rack with just the pre-amps and eq with insert points and output post eq.
I was wondering if I could combine this with a summing mixer by adding a pot on each channel and a button to route to the L/R instead of the Direct Output.

So let me se if I've got this right: Basically, you want to take a perfectly good rack-mounting mixer, hack it to bits, and then rebuild it in a rack to make... a mixer! Er.. I think that requires one of these: :headbang:

Just after thoughts on whether this will work and any tips on proceeding.

Not easily. So you want to keep the pre-amp, insert point, EQ, direct output, and fader (pot) for each of the eight channels? So you actually only want to lose the Aux sends and surplus channael routing, and the monitoring output section... or perhaps you want to keep taht too, so you can hear what your mix is doing. And maybe some PFL to check channel levels, and perhasp an odd Aux in case you needed a separate mix for something...

As I recall each channel is built on a separate channel PCB, and it really wouldn't be practical or even possible to separate out the bits you want from the rest of the signal path that you don't. So you'd be committed to using the original PCBs unless you rebuild from scratch (in which case, flog the Soundcraft and build a new mixer from scratch -- it will be easier and cheaper). And if you're going to use the original PCBs, you might as well use the original channel strip metal work to support it adn the controls. You could saw off the fader section at the bottom if you wanted, but why?

And as Dave says, the cost of the metalwork to rehouse it makes this a pointless exercise.

What's wrong with the mixer as it stands? What can you gain by rehousing it? it's perfectly rackable as it is...

H
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Re: Pre amps rack/ summing box

Postby JPHogg » Fri Jan 25, 2013 1:01 am

Thanks for the replies.

The desk hasn't got direct outs at the moment but it would be a simpler solution to look at adding these rather than hacking and rebuilding it.

I couldn't afford to pay anyone to do any of this but we're quiet at work atm so have got a bit of time to play. I will however take the advice gratefully and just look at a way off modding the mixer.
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Re: Pre amps rack/ summing box

Postby ef37a » Fri Jan 25, 2013 6:50 am

If you go to the Soundcraft site you will find a manual with signal diagrams and a schematic.

Personally I would simply build a box of jacks and use the inserts as direct outs (linking tip and ring) It is a shame that these are post EQ but 1) it might be fairly easy to move the pickoff point and 2) most folks track "flat and dry" these days anyway.

If Soundcraft peeps are anything like A&H bods I am sure they will advise.

Dave.
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Re: Pre amps rack/ summing box

Postby Matt Houghton » Fri Jan 25, 2013 1:50 pm

+1. It's a perfectly decent little mixer, and it would be way cheaper to buy something new that does what you want and comes with a warranty. You'd be getting into chopping up the PCBs which is an accident waiting to happen. And as has been suggested, with the right cables (which are relatively cheap to buy/make/have made) you can use the insert points as direct outs.
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Re: Pre amps rack/ summing box

Postby Hugh Robjohns » Fri Jan 25, 2013 4:27 pm

JPHogg wrote:Thanks for the replies.

The desk hasn't got direct outs at the moment but it would be a simpler solution to look at adding these rather than hacking and rebuilding it.


If you don't want to use the inserts to provide direct outs, which is the easiest option, if not the safest, then perhaps you can get you tech to build a pcb with a bunch of TLO74 op-amps wired as buffers, taking their inputs from the preamp out, and provide direct outputs that way. You'll just need to find somewhere to fit a 25 pin D-sub connector, and wire to the Tascam standard. As Dave says, you can access the schematics from the Soundcraft site.

H
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