differential 8 - 1 audio mix

A project log for Multichannel Audio DSP Field Mixer Recorder

bluetooth app controlled professional portable DSP mixer.balanced audio IO,phantom power,flexible routing,ISO recording. timcode. AVB audio.

ben bilesben biles 09/09/2015 at 05:580 Comments

OK, time for a compromise :(

I am going to settle for 2 x 8 - 1 analouge mix downs for the 2 channel output.

I'm going to try using a THAT1606 OPAMP differential line driver for the XLR outputs

some specs that sold me where

"Balanced, transformer-like floating output

Stable driving long cables and capacitive loads

High output: 18Vrms into 600Ω

Low noise: -101 dBu

Low distortion: 0.0007% @ 1kHz"

At some point mixer has to go Analouge for the outputs so I thought It may as well be here.

I have to use +/-15v ( approx ) clean power supply for the THAT1606 so I went for the new


I can use 2 x DACS for a repat of the 8 inputs and balance by incrase / decrease the copied channel.

BUT, how can I make a master volume control ? or a headphone monitor ?

say2 x LM1972 digatally controlled attenuators or 4 channel PGA4311. but there both single ended !! ahhhh !!!! audio needs to stay differential all the way out !!! I'll work that one out later !!

well, i ordered the 2 x THAT1606 and power supply. I have no idea what resistors to use to devide the 8 outputs ( 16 differential resistors per channel output ) down to normal level. I guess I'm dividing equally by 8 so they should all be the same but what value resistor to use?

DAC outputs are;