Question about summing amplifiers and discrete devices for high quality audio sound

[avdrummerboy]

Hi, I am designing a three channel mixer of sorts for audio. I was wondering what amplifier is best suited for summing the three sources ( I want to keep it stereo so there will be two.) I was planning on an emitter follower but if anyone has a better way please let me know.

Also, to kill two birds with one stone, what discrete (no op-amps here) device in your opinions is the best for fairly high quality audio sound. I don't need or want to go overboard on hi-fi but good sounding would be nice.

 

[FvM]

summing amps

Current input summing amplifiers have been used in mixing consoles since ever, with OP or discrete transistors as well. But negative feedback in amplifiers is advisable to achieve low distortion, stable gain and low summing node impedance.

 

[Audioguru]

summing amps

The OPA2134 dual opamp has 0.00008% distortion.
The LM4562 dual opamp has 0.00003% distortion.
Both have very low noise.

A discrete circuit might have distortion that is 1000 times higher or more.

 

[FvM]

summing amps

And a good discrete circuit may achieve competitive results.

For I obvious reasons, I don't prefer a discrete solution. But as it was explicitely requested, I just wanted to mention that it's possible and has been used in the ages of IC-less audio equipment.

Just consider a sufficient bias, feedback class A amplifier. It's a bit more than the said emitter follower however.