Balanced B1 preamp

[notesman50]

Folks, I assembled the Pass DIY class A kit, building two units each used in balanced mode. I'd really like to build a Pass designed preamp but require balanced inputs and outputs. Based on my somewhat simplistic understanding of balanced operation I figure one could use two stereo preamps with the two channels used for the Positive and Negative signals with a common gnd. This would be somewhat cumbersome to operate but no different from two mono preamps.
My apologies if this issue has been addressed before and please feel free to inform me of my ignorance.
Regards, steve

 

[wrath]

Easiest Way - 2 irons per Channel.. Before buffer for debalancing. After for balancing. Galvanic isolation for free...

 

[Zen Mod]

it's always best having proper differential stage than two SE ones working in antiphase and being completely unaware of each other

 

[fmplayer]

But what if your surrounding DAC and amp have balanced I/O ?

 

[Loudthud]

Just curious, what do you use for a Volume control in a balanced system ?
Most studio gear is SE internally with transformer coupled I/O for common mode isolation. Most of the work I've done with balanced circuits was inside of analog oscilloscopes. Not really the same as balanced audio.

 

[fmplayer]

What I had in mind was something like this

 

[Zen Mod]

pic no good , at least on my side

even "open in new tab" is not working

 

[fmplayer]

B1 Balanced

Sorry. Let's try this one

An externally hosted image should be here but it was not working when we last tested it.

 

[Zen Mod]

in principle , it should work

though, I always avoided stacking CCS-es, so can't say how stable is going to be

try, and report

 

[fmplayer]

Balanced B1

Second option would be with I/O transformers and without the current source. No risk (I have no measuring stuff but a multimeter) but it's more expensive (100$ each, 2 per channel).

 

[fmplayer]

Balanced B1

Or maybe better, the salas version, where each channel would have its low noise +/- 9V supply.


Maybe simple could be beautiful. Thanks in advance for your opinion

 

[fmplayer]

Balanced B1

Ooops. I attached an intermediate version with wrong input resistor values on the - side.


Here is the correct one