Converting unbalanced direct outs to balanced

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psb_87

Active member
Joined
Aug 3, 2017
Messages
42
Hi all,

I've tried the search function but couldn't find anything covering this, but please forgive me if it has already been covered.

I have the chance to buy an Allen & Heath Saber 8 and would like to convert the unbalanced direct outs to be balanced.  From what I've managed to find out there are two ways of doing this; transformer based or opamp based.  The former being the pricier option but potentially sweeter sounding.  However, I will probably not be able to afford this so I am looking at achieving balanced outs without transformers.

In my search I have found a very simple and neat little PCB kit for this purpose (unfortunately discontinued, but easy to replicate):

https://www.diyrecordingequipment.com/products/balanced-output

Would something like that work if I was to incorporate one of these on every single direct out for each channel strip? If so, would it just be a case of cutting the circuit where it feeds the direct out and replacing it with one of these?

Sorry for my noobish knowledge, I am still very much learning.

Thanks in advance, any info would be much appreciated
 
Unless you are wanting to do this because of noise concerns, like from long runs of cable, I'm not sure I see the benefit?

Besides, unbalanced rules unless you're talking a truly balanced system imo.....


Sorry this questions and not answers......

Hopefully you'll find your answer here.......Seems you are looking at the right stuff for what you're after....

Good Luck
 
scott2000 said:
Unless you are wanting to do this because of noise concerns, like from long runs of cable, I'm not sure I see the benefit?

Besides, unbalanced rules unless you're talking a truly balanced system imo.....


Sorry this questions and not answers......

Hopefully you'll find your answer here.......Seems you are looking at the right stuff for what you're after....

Good Luck

Thanks a lot for your feedback.  The reason I'd like to convert them to balanced is indeed for noise reasons, I don't like the idea of noisy lines going straight into my interface to be recorded.  Seems like every piece of unbalanced equipment I've ever owned has always had some noise issues from interference to hum.  I'd just prefer to not chance it when recording clients, though I am open for persuasion to the contrary.  When you say unbalanced 'rules' what do you mean by that? from the research I've done there is little to no benefit to unbalanced audio other than cost?
 
RuudNL said:
This will do the job:
http://www.thatcorp.com/datashts/THAT_1606-1646_Datasheet.pdf
(In fact the same a s the discontinued kit.)

Thank-you yet again, I will give this a good look.
 
I would look at impedance balancing your outputs, it's literally a single resistor per channel and gives very good immunity to noise and hum.  As long as your balanced/differential input on the interface sees equal impedance on pins 2 and 3 you will have no problems.  It also saves mounting and powering ICs and PCBs in your console.

You will likely not get as much output level as you would with a dedicated balanced output but you may have enough.  What interface are you using?

Do you have a schematic for the Saber 8 direct outs?
 
psb_87 said:
Thanks a lot for your feedback.  The reason I'd like to convert them to balanced is indeed for noise reasons, I don't like the idea of noisy lines going straight into my interface to be recorded.  Seems like every piece of unbalanced equipment I've ever owned has always had some noise issues from interference to hum.  I'd just prefer to not chance it when recording clients, though I am open for persuasion to the contrary.  When you say unbalanced 'rules' what do you mean by that? from the research I've done there is little to no benefit to unbalanced audio other than cost?

Hopefully others can chime in with their opinions and experiences as I'm short on time now but, unbalanced gear in a normal setting can be quite advantageous over balanced in some scenarios.  Unbalanced isn't noisy by design. It's just more susceptible to issues around noise and, usually longer runs of cable have more chance of picking this noise up. I'm sure balanced has more driving advantages as well but, in my experience, unbalanced seems to be more than acceptable if not preferable.

One example, that may relate to your scenario, is that I had a compressor that has unbalanced and balanced inputs/outputs.  The compressor, as many pieces of gear are, is really unbalanced internally.

The extra stages are where the signal transparency can be affected. Of course this is subjective but, when I use the balanced outputs of this compressor, the balancing circuit adds 2 op amps, a number of large and small capacitors and some resistors to make it balanced. The signal bypasses this balancing stage if I use unbalanced and I hear a difference that is not subtle.

I hope this explains some. Bob Katz is a mastering guy here where I live and he has written some stuff on this. I've tortured myself making cables and remaking them to try to test my set up for the differences and, I'm just about unbalanced everywhere. And my system is as quiet as can be unless you listen to the circuit ,op amp noise and other things that are just always there...Not sure why you experience it differently... Could be other issues.

Schematics are helpful in seeing how your gear works and if there are major advantages either way. Then you could just make you some cables and hear for yourself.

It is a rabbit hole so, be aware that there are considerations when sending your balanced gear unbalanced signals and especially vice versa...

Good luck...
 
Hey thanks a lot for your detailed reply.  I've also read a bit about unbalanced producing a truer, uncoloured sound and therefore preferable amongst mastering engineers especially.  The thing that is making me question this logic is why API and Neve amongst others would go to the effort of providing transformer balanced direct outs on the majority of their consoles.  I am unaware of any big time studios that would have unbalanced direct outs feeding their top of the range converters etc, but I will gladly accept it if I am wrong.  I suppose the argument here for having transformer balanced outs could purely be for sonic reasons i.e. the transformer is largely what is providing 'the sound' that people have come to love from these consoles.  But surely the majority of that comes from the input transformers and pre-amp in general rather than purely the output transformers, and if an unbalanced out would provide a higher quality, purer signal then these manufacturers would be the first to employ such technology on their top line desks? Maybe I just do not know what I am talking about?
 
ruairioflaherty said:
I would look at impedance balancing your outputs, it's literally a single resistor per channel and gives very good immunity to noise and hum.  As long as your balanced/differential input on the interface sees equal impedance on pins 2 and 3 you will have no problems.  It also saves mounting and powering ICs and PCBs in your console.

You will likely not get as much output level as you would with a dedicated balanced output but you may have enough.  What interface are you using?

Do you have a schematic for the Saber 8 direct outs?

Hey thanks a lot for your reply, I haven't heard of this solution but certainly looks like a great option, I'll have to look in to this as it could be a really cheap and quick fix!

The interface I will be using will actually accept unbalanced connections, I just assumed I would be better off with balanced connections if possible.  It's a MOTU 24io with PCIe card.

I am working on getting the schem for the saber 8, I think it will largely be the same as the other saber versions but will be able to confirm for sure when i get  a chance to open up the desk.  Cheers!
 
musicaudioworks said:
Unbalanced signals have more signal integrity than balanced signals.

I disagree, since an unbalanced signal is defined only in terms of "ground", an external and difficult to control voltage reference, whereas a differential signal is self-defined, independent of any other voltage.

Furthermore, when you send a balanced signal to a balanced load, there is no net return current that has to flow within ground between the two pieces of gear - the positive and negative halves of the transmitted signal current cancel at the load.

With an unbalanced transmission, not only is signal referred to ground, but signal current must flow in the ground between the two devices, guaranteeing some level of common impedance coupling.

Unbalanced signals are inherently worse. And, balanced amplifiers can actually be cleaner than unbalanced, so it's not simply the case of "adding more stuff to an unbalanced circuit" to make it balanced. Most pro audio gear treats balanced signaling as just that - only reserved for signaling between the IO jacks. However, if you design a device to be internally balanced, you'll find that a lot of extra circuitry can be removed - there's no need to unbalance and re-balance a signal if you leave it balanced throughout the circuit.

Yes, you will generally have to spend more money on extra components to make an internally balanced circuit, but let's call that a cost / performance tradeoff, and not call the single ended signaling device any sort of inherently better performing circuit just because it costs less.
 
wow, too much nonsense to address it all...

There is absolutely nothing wrong with short unbalanced audio interfaces.  I never balanced DOs or inserts on even premium consoles (while some do when conditions warrant it, like long sends).

What is important is maintaining signal integrity. If the console is well designed the signal will be clean wrt to the jack ground or audio low (usually by using an internal differential stage inside the console).  Any decent receiving gear will use a differential or balanced input. For clean audio transfer you need to grab the signal differentially from that output jack. So differential in + connects to the send tip, differential in - connects to jack ground, and the cable shield is floating (or connected through a RC).

Problems can occur if there are different ground voltage potentials and a hard connection between those two chassis allows current to flow in that ground lead, corrupting any audio signal in that same lead, so avoid hard ground connections (at least in any audio paths).

JR
 
scott2000 said:
One example, that may relate to your scenario, is that I have a compressor that has unbalanced and balanced inputs/outputs.  The compressor, as many pieces of gear are, is really unbalanced internally. Meaning, it takes the balanced input and unbalances it and....takes that unbalanced signal and re-balances it on the way out. This particular compressor lets me choose if I want to use the unbalanced jacks for input and output so, it doesn't have to go through these balancing/unbalancing stages. It just stays where it is.

Yes, most gear is unbalanced on the inside, for a variety of good reasons. Balanced I/O is intended to minimize noise from the environment.

You should look at the schematic of that compressor and see if the unbalanced inputs and outputs are really separate from the balanced. What compressor is it, anyway? My guess is that they're the same circuit, that is, the unbalanced connections go to the balanced electronics. Which is standard.

The extra stages are where the signal transparency can be affected. Of course this is subjective but, when I use the balanced outputs of this compressor, the balancing circuit adds 2 op amps, a number of large and small capacitors and some resistors to make it balanced. The signal bypasses this balancing stage if I use unbalanced and I hear a difference that is not subtle.

That sounds like a design problem, not a problem with the notion of balanced interconnects.
 
JohnRoberts said:
wow, too much nonsense to address it all...

There is absolutely nothing wrong with short unbalanced audio interfaces.  I never balanced DOs or inserts on even premium consoles (while some do when conditions warrant it, like long sends).

What is important is maintaining signal integrity. If the console is well designed the signal will be clean wrt to the jack ground or audio low (usually by using an internal differential stage inside the console).  Any decent receiving gear will use a differential or balanced input. For clean audio transfer you need to grab the signal differentially from that output jack. So differential in + connects to the send tip, differential in - connects to jack ground, and the cable shield is floating (or connected through a RC).

Problems can occur if there are different ground voltage potentials and a hard connection between those two chassis allows current to flow in that ground lead, corrupting any audio signal in that same lead, so avoid hard ground connections (at least in any audio paths).

JR

regarding 'hard grounds' - well it 'all depends' as the saying goes but the link below (I hope I've inserted hyperlink properly makes interesting reading. I realise it probably doesn't relate closely to the OP's situation.

Yes - it's an advantage if the receiving circuit is differential or balanced. But (esp with a 'simple' electronically balanced Diff amp receiver) you will get a better result if the sending end is impedance balanced.

[urlhttps://www.resolutionmag.com/wp-content/uploads/2016/02/The-correct-way-to-bond-shields.pdf][/url]
 
Newmarket said:
regarding 'hard grounds' - well it 'all depends' as the saying goes but the link below (I hope I've inserted hyperlink properly makes interesting reading. I realise it probably doesn't relate closely to the OP's situation.
It is generally good to avoid commingling grounds with audio lines and that is only routinely done with consumer gear.
Yes - it's an advantage if the receiving circuit is differential or balanced. But (esp with a 'simple' electronically balanced Diff amp receiver) you will get a better result if the sending end is impedance balanced.
Only if sending audio over significant distance, with poorly shielded wiring, in a noisy environment.  For short interfaces in a reasonably benign environment single ended sends have worked fine for decades. On the receiving end where it is cheaper to do, differential treatment is widely used.

Impedance balanced is indeed worth the extra penny for long truly balanced interfaces. For a short interface with a differential receiver I do not expect much (any?) difference.  Those one cent impedance balance resistors are money well spent by manufacturers so they can say "balanced" in their marketing.  ;D
[urlhttps://www.resolutionmag.com/wp-content/uploads/2016/02/The-correct-way-to-bond-shields.pdf][/url]
As usual we have strayed from the OP's question about adding a balanced output.  In my judgement it is an unnecessary expense and effort if the wiring is handled sensibly (perhaps check the Rane notes on wiring).

wrt to posting urls your link has one of the square brackets after the url address instead of in front..  perhaps a cut and paste error 

https://www.resolutionmag.com/wp-content/uploads/2016/02/The-correct-way-to-bond-shields.pdf

this should display better and work but I didn't check if there is any there there. 

JR
 
JohnRoberts said:
As usual we have strayed from the OP's question about adding a balanced output.  In my judgement it is an unnecessary expense and effort if the wiring is handled sensibly (perhaps check the Rane notes on wiring).

wrt to posting urls your link has one of the square brackets after the url address instead of in front..  perhaps a cut and paste error 

https://www.resolutionmag.com/wp-content/uploads/2016/02/The-correct-way-to-bond-shields.pdf

this should display better and work but I didn't check if there is any there there. 

JR

Yes. We have strayed. We can't help ourselves  ::)
But yes, I take the point that the balancing - however done - may not be just justified.
I'm not familiar with the A&H Saber - although I do have a GL2 - but I imagine it's quite a lot of effort to get inside to mod ?
I'd be tempted to try and do it within the connector shell although there's then the issue of whether the shield connection is the optimum - chassis or signal ground etc - depending on the design detail.

re URL - yes I can see my error - I think I must have done that previously on a differeent topic too - I'll blame my eyesight/spectacles/screen  :-\
Thanks for pointing it out and yes the link you posted works.
 
Hey everyone, I greatly appreciate all of your input and informative replies.  I spoke to Allen & Heath directly on the matter and they actually used to offer a balancing kit for the console.  Looks like a really simple and inexpensive circuit:

http://www.allen-heath.com/media/EBOS-BALANCED-OUTPUT.pdf

I guess I will just hook everything up when I eventually get my hands on it and see what happens.  If I need to balance the direct outs then at least I can use this schematic to do so.

JohnRoberts said:
wow, too much nonsense to address it all...

There is absolutely nothing wrong with short unbalanced audio interfaces.  I never balanced DOs or inserts on even premium consoles (while some do when conditions warrant it, like long sends).

What is important is maintaining signal integrity. If the console is well designed the signal will be clean wrt to the jack ground or audio low (usually by using an internal differential stage inside the console).  Any decent receiving gear will use a differential or balanced input. For clean audio transfer you need to grab the signal differentially from that output jack. So differential in + connects to the send tip, differential in - connects to jack ground, and the cable shield is floating (or connected through a RC).

Problems can occur if there are different ground voltage potentials and a hard connection between those two chassis allows current to flow in that ground lead, corrupting any audio signal in that same lead, so avoid hard ground connections (at least in any audio paths).

JR

Hi John, thanks for the great amount of information and for correcting some misinformation.  I'm interested in the high end consoles you mention here that have unbalanced direct outs?
 
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