So after years one planning to do this, I finally got around to it. Here are the results:
Simple TL074 based mixer with stereo pots for each channel that fits to the existing holes. I’ve got a handful of boards if anyone would like one and then I’ll post a OSHpark link so anyone can get them any time.
Boards:
https://oshpark.com/projects/iEI4Yrhq
BOM
https://docs.google.com/spreadsheets/d/1w-VEWmPBQucrhK-vZdvH8pU_xwDvS5GS1VtrLofj800/edit?usp=sharing
Just to clarify, these do away with the feedback pots and basically replaces them with volume knobs? Do they affect the individual outs at all or only the mix out?
Correct. There are 2 ways to wire this in, pre the jack which will just mirror what’s coming out of the channel or post jack by puling the 10ks in the passive mixer so the SID pair is removed from the mix when you plug something in
Looks an interesting add-on, but I do like the feedback pots!
Is it single supply? What op amp? How large are the DC blocking caps?
I like the feedback as well but its REALLY cumbersome to use the MB6582 with a 8 channel snake out the back. I used a single supply with TL074 running off the 9V
This is great !!! i want it
do you plan on selling your boards ? if so how much do you want for one ?
cheers
Are all the boards gone? PMed you after you posted this…
no, just havent had time to deal with this..
Is there a board left? I’d be happy for one.
i’ll PM ppl for the ones I have, $5 a pop. I’ll post an OSHpark project later..
Not receiving a pm from you means all boards are gone?
payment requests sent.
Here is the BOM
https://docs.google.com/spreadsheets/d/1w-VEWmPBQucrhK-vZdvH8pU_xwDvS5GS1VtrLofj800/edit?usp=sharing
PCB received a few days ago. Thank you very much! Now it’s just about to source the pots. 
I just ordered PCBs from OSHPark - it cost the same to get 3 boards vs 1 ($10.30), so if anyone wants to buy one from me for $3.43+shipping, let me know.
I am in for one tnx.
Just now, ganchan said:
I am in for one tnx.
Ok, I’ll contact you once they arrive.
I received the PCBs for the addon Mixer. I have 2 extra. I sent a PM to Ganchan. Let me know if anyone else is interested.
Justin
I’ve just picked up 3 of these board, so I have 2 extra in EU, if there is anyone interested please contact me.
Also, does anyone know where to source these pots in Europe?
Can the TL074D run off 12v in a 6581 SID setup? Or would I need to regulate it down to 9v?
Also, would these be suitable replacements for the dual ganged pots? Are these the same Alphas?
12v is fine.
