Solder Post-EQ Direct Outs on an Allen & Heath SR8

[Tedward]

So I picked up an SR8 really cheap a while back because the pres get rave reviews on forums. I figured I could use the main outs and aux sends to get 6 invidual outputs, but when I actually attempted this, I found that all the channels seem to bleed. Even panned 100% Left, a channel will still feed a tiny amount of signal to the Right output. Furthermore, sending a signal to one aux sends a small amount of the signal to every aux, which I find even more bizarre. Not a problem at all for live, or even for the studio if the full mix was being done entirely on the board, but I wanted to use the 8 beautiful pres and eqs to feed into my DAW individually so I could keep mixing. I found an old thread on the subject, which I can't link to because I'm a newbie and they don't let you until you've posted a few times. I find this irratating, seeing as how I went to reply to that thread, and the site asked me to start a new thread and link to the old one instead of bumping. Ah well. I'll try to post the link in the comments. The title was: Mod Allen & Heath for direct outs? The OP wanted to mod their SR16 for post EQ individual outs. Initially, people encouraged him, but the thread ends with two very negative replies, asserting that attempting this mod would likely wreck the board. I'm wondering if anyone has any experience with this type of thing and could help me out. Thanks!

P.S.
The last poster on the old thread tells the OP to just use the inserts as direct outs, which would work, except I love running things through guitar pedals with those inserts . Also the inserts are pre EQ, which would be a bummer, because the eq is not half bad.

 

[Steenamaroo]

Hi Tedward,
As far as I know the 'bump old threads' thing is a friendly warning but you should be able to proceed if you want.
It's there because people often bump really old threads, without realising, having found them in searches etc.

Anyway, I've promoted you to full user so you should be able to link etc now.

Hopefully someone can tell you if that bleed is considered a fault or just a 'feature'.

 

[Tedward]

Thanks, I'll bump the old thread and see if I get anything!

 

[ecc83]

I cannot find schematics or even a decent signal block diagram for the mixer however, I would urge reading a copy of Duggy Self's Small Signal Audio amps" before embarking on any such project.

Specifically (as I think someone alluded to in the other post) you need to be sure you don't load down the internal circuitry. At best you might screw gain and pan pot laws, at worst cause loss of headroom and distortion. Even instability.

First task, talk to A&H and see if they can supply schematics.
Next, identify the take off points in the mixer.

Then build a 'buffer box' with 4 NE5532s with say, 100k input Zs and coupling cap of the right value (and polarity! Test for it!) An economical way to connect into the mixer would be to use the Tascam D-sub connection protocol.

The outputs of the unity gain 5532s can be impedance balanced if you like or/and appropriate.

You could power the B box from a 30Vish rat and use either a resistive splitter or GRMad and use an opamp to derive a 'centre rail'. I would not advise pulling any more juice from the old mixer's supply.

Dave.