Increase in use of 'impedance balanced' outputs

[ruffrecords]

I am beginning to detect a significant increase in the number of products whose outputs are impedance balanced. The reasons are obvious - it is a simple cheap way to obtain most of the benefits of balancing. This seems to happen mostly on multi-channel 'interfaces' designed to be attached to a PC. I have noticed some discussion of Slutz about whether or not this is a con (or just a lack of understanding). I have also corresponded with several people who have contacted manufacturers about the balanced outputs of their products who have been told without exception that they are impedance balanced ( the last one a few days ago).

So, are we about to see the end of differential balanced outs?

Cheers

Ian

 

[JohnRoberts]

I am beginning to detect a significant increase in the number of products whose outputs are impedance balanced. The reasons are obvious - it is a simple cheap way to obtain most of the benefits of balancing. This seems to happen mostly on multi-channel 'interfaces' designed to be attached to a PC. I have noticed some discussion of Slutz about whether or not this is a con (or just a lack of understanding). I have also corresponded with several people who have contacted manufacturers about the balanced outputs of their products who have been told without exception that they are impedance balanced ( the last one a few days ago).

So, are we about to see the end of differential balanced outs?

Cheers

Ian

This is not really recent... Mackie, remember them? pioneered the use of "impedance" balanced outputs last century while marketing them as "balanced"  : with massive ad campaigns.

This is an old topic and well inspected.  IMO impedance balanced is as good as active balanced for 99.9% of modern applications and only a tiny fraction of the cost.

I approve that cleverness (Greg got a lot of marketing benefit from those $0.02 resistors) but I didn't appreciate the loss of market share (from all the advertising), while few consumers had a clue about what was what.

There are multiple active balanced output driver chip sets so those will still win premium SKU design-ins because of their +6dB hotter output level... that "looks" good on data sheets.

Consumers will still believe that more is better...  :

JR

 

[abbey road d enfer]

In a world of 3.3V ADC, who needs +26 dBu outputs?
In terms of signal integrity, a simple opamp will beat a CCOS anytime.
I respect very much THAT's developments though.
Modern (digital) equipment is designed to operate differently than the legacy analog, which offered its better performance compromise at about 15-20dB below its max.
Digital stuff is designed to operate closer to its maximum, since in the digital realm, more used bits is better; the surrounding analog stuff is optimized for operating at this elevated level.
Of course, the compromise is different for hybrid (old with new) set-ups.

An advantage of CCOS vs. Z-balanced is that connection to an unbalanced receiver provides noise rejection.
The circuit used by Soundcraft (Doug Self's?) does it too.

 

[john12ax7]

I generally prefer impedance balanced when not using a transformer.

 

[Bo Deadly]

You can't assume outputs are going to ADCs. There's lots of outboard gear that might be in the path that needs a higher level for noise performance and / or to provoke it's mojo like compressors and such. But -6dB is not a problem. Impedance balanced outputs are dandy for just about anything except maybe driving really long lines.

 

[Michael Tibes]

It took me a while to understand it's pros and (in my opinion) lack of cons for my own designs, now I'm a fan ;-)

Michael

 

[emrr]

As good a (recent) place as any:

Reading ‘The Emergence of Broadcasting in Britain’ I see the date 17 May 1923 when engineers desperate to make radio distribution through telephone lines without crosstalk, first tried balancing the lines to perfect success.   

The funny bit is the original power calculations suggested they needed to drive the lines with 40W. In the end that was dropped to 1mW, still unsatisfactory, before they tried balanced lines. 

 

[user 37518]

You can't assume outputs are going to ADCs. There's lots of outboard gear that might be in the path that needs a higher level for noise performance and / or to provoke it's mojo like compressors and such. But -6dB is not a problem. Impedance balanced outputs are dandy for just about anything except maybe driving really long lines.

Agreed, however in the case of mic pre's, a lot of people are going straight to ADC.

 

[RSRecords]

Random Impedance balancing question, probably not worthy of a new thread. With a stereo (2ch) output. Could you use the same resistor to ground connection for both channels? So separate 100R to pin 2 for each channel. Both channels share the same pin 3 100R to ground.
1-way street to crosstalk city?

 

[JohnRoberts]

Random Impedance balancing question, probably not worthy of a new thread. With a stereo (2ch) output. Could you use the same resistor to ground connection for both channels? So separate 100R to pin 2 for each channel. Both channels share the same pin 3 100R to ground.
1-way street to crosstalk city?

Probably OK for typical stereo playback... For perspective about stereo crosstalk, look up separation specifications for vinyl playback cartridges (hint: it isn't much). So, yes it could be a source of crosstalk, but unlikely to be a problem with typical stereo program material.

JR

 

[abbey road d enfer]

Random Impedance balancing question, probably not worthy of a new thread. With a stereo (2ch) output. Could you use the same resistor to ground connection for both channels? So separate 100R to pin 2 for each channel. Both channels share the same pin 3 100R to ground.
1-way street to crosstalk city?

Yes, cross-talk (note it would be out-of-phase, so maybe beneficial for vinyl ), but also CMRR all over the place.