NY Dave 600ohm mixer build completed

rockinrob86 said:

The apollo has 600 ohm outs, which is why I said that.  I still don't understand impedance bridging, I should research that.

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An output that is capable of driving a 600 ohm load will also drive an higher resistance load - like 10K. In fact it will drive quite a few of them. You don't really need to know much more than that at this stage

My plan was to run the 8 600 ohm outs of the apollo into a simple mixing board, with some outboard in between for some channels- for instance a spring reverb, an echoplex, a plate reverb if I ever get around to building it, a compressor or two, etc.

It would be something like:
Output 1 - Bass out to 1176 into mixer channel 1
2 acoustic guitars (summed in DAW) into mixer channel 2
3 rhythm guitar (panned left) into mixer channel 3
4 lead vocal out to echoplex into mixer channel 4
5 and 6 drums (summed in DAW) into mixer channels 5 and 6
7 lead guitar with panning effects into mixer channel 7
8 reverb sends summed from DAW out to reverb unit into mixer channel 8

Then plug the stereo out of the mixer into two mic pre channels and record the mix/mixes back into the DAW

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Sounds like a simple passive balanced mixer will do this for you. It is not 100% clear from your description but it looks like the inputs only need to be panned left, right or centre which would simplify things.

I have two spectrasonics model 101 cards I have been planning on using to build mic pres with, but I could use them as line amps for the output of this mixer - especially if I use it all the time.  I could wire it in "permanently" into two line in channels in the apollo.

Would it be best to keep this balanced?  in the schematic the first transformer is just converting the input to unbalanced, right?  what would the input impedance of this on be?

I'm also thinking of adding another apollo at some point to get more UAD processing power, and I could use that to expand this whole rig to 16 track outs, but I think it would be best to design and build another mixer then after learning from mixer 1.

So what should I do for this?

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Two approaches are possible. You could unbalance each input with a transformer and mix unbalanced then balance again at the output. This is pretty much how a conventional mixer works (as illustrated in the NYD general purpose mixer schematic). Or you could make is as a balanced summer, perhaps with LCR pan switches and use the spectrasonics as a transformer balanced input gain make up amplifier.

Cheers

Ianj