Balanced vs Unbalanced - maybe there is something in it after all

[rkbates]

I found this pretty interesting - not an audio application but the principle is the same. Measurements are on a CAN control bus in an grid connected inverter. Heaps of noise on the signal lines (that's another problem - still being investigated). Sorry about the measurement quality, a 10 MHz 8 pit Picoscope was all I could fit in the overloaded toolbox and still be allowed on the plane. Anyway, although the CAN Low and CAN High were unusable, the differential on the twisted pair had most of the common mode noise cancelled out (purple trace at the bottom) was good enough for the application. Always nice to see the theory play out in practice.

 

[DonH56]

The PCIe, SATA, USB, Ethernet, SAS (if you have such), devices inside your computer all use differential signaling because they reject common-mode noise. Your audio DAC (almost certainly) has a differential output, converted to signal-ended by the output buffer if desired.

Hand-waving thread:

Differential, Single-Ended, Balanced, Unbalanced, and all that jazz...

I posted this picture over on WBF in the middle of a long semi-fruitful discussion on the benefits and drawbacks of differential operation. Ken Newton suggested sticking with the accepted technical definitions and distinction among differential vs. single-ended and balanced vs. unbalanced that I...

www.audiosciencereview.com

 

[MaxwellsEq]

For many years the HiFi press claimed balanced / differential sounded less good than single-ended. Their logic, if I recall properly was balanced /differential required more components and sometimes more wire. Because I worked in audio studios I thought this attitude was bonkers.

 

[staticV3]

What's cool is that you don't need differential signal output for high CMRR.

You can have a single ended, impedance balanced output connected to a differential input and get all the CMRR advantages.

 

[Alexander Gödde]

For many years the HiFi press claimed balanced / differential sounded less good than single-ended. Their logic, if I recall properly was balanced /differential required more components and sometimes more wire. Because I worked in audio studios I thought this attitude was bonkers.

Unfortunately, most of today's HiFi press is bonkers.

 

[Speedskater]

a CAN Control Bus needs a well behaved transmission line to operated correctly. (i won the Tee shirt)
Analog and most digital interconnects don't have those kinds of problems.

 

[rkbates]

a CAN Control Bus needs a well behaved transmission line to operated correctly. (i won the Tee shirt)
Analog and most digital interconnects don't have those kinds of problems.

But it can take a lot of abuse before it fails to operate at all, especially at low baud rate. Still no excuse for lazy design.

 

[Fredygump]

I personally like that balanced connections are much more robust connections.

And recently I was able to compare the noise from balanced vs unbalanced. I purchased a new device (minidsp HTx), and I wanted to test it right away. But I hadn't received my new TRS connectors yet, so all I had were RCA cables. I invested zero effort into wire management, and I got audible ground loop type noise in my horns.

When I got my TRS connectors, I re-made my old XLR cables and reconnected everything with balanced cables. The noise was gone.

(Certainly careful wire management would also have fixed most, if not all of the noise, but balanced is physically more robust, and it is more forgiving of cable management issues. I like it, even if I don't need it.)

 

[Speedskater]

But it can take a lot of abuse before it fails to operate at all, especially at low baud rate. Still no excuse for lazy design.

You would think so.
But system hook-up errors, caused problems on the lab floor. And similar problems caused problems in a hospital system.
(that was 25 years ago. don't remember much more)