Mixer mod - from where to take output?

robinbowes

I've got an ex-BBC 7 balanced input stereo mixer with only headphone outputs. I'm adding balanced stereo outputs and have built a couple of balanced output modules [1].

This is the left output circuit:


IC7a is a summing amplifier that combines the seven inputs.
VR7 is the master volume
IC8a and TR2/TR3 are the headphone driver circuit.

My question: from where should I take the output to feed to the balanced output module?

The two obvious places are:

1. the junction of R117 and R122
2. the junction of R117 and C95

I don't suppose it will matter a great deal but has anyone got any comments on the relative merits?

Or am I over-thinking this?

R.

[1] https://www.diyrecordingequipment.com/products/balanced-output

robinbowes

I finished this project over the weekend.

To re-cap, I had a mixer with seven balanced stereo inputs and two headphone outputs, and I wanted to add a balanced stereo output.

I replaced the channel 7 input sockets with output XLRs:



I took unbalanced outputs (the brown wires) and power (red/black/white wires) from appropriate points on the PCB:



I fed the inputs and power to two balanced output modules, the outputs of which go to the output XLRs:



The veroboard on the right is just a breakout board to make it easier to provide power and ground to the two balanced output modules.

A larger picture:



I may convert channel 7 to RCA socket input, for convenience, but I need to figure out where I can squeeze a pair of phono sockets in the chassis.

All-in-all, a great success so far.

R.