Practical benefits of balanced cabling

Continuing the discussion from 1/4" vs. 1/8" connections:

The above made me curious to open a discussion about balanced cabling. My experiences have mostly revolved around live performance of laptop based music, and some medium-fi home recording. My prejudice is to say that I rarely find balanced necessary, and can’t think of a time when changing to a balanced connection solved a problem. Nor can I think of a time where I wish I could go back and re-do a given task with balanced connections.

I’ve always thought of balanced as being important in two specific cases:

  • Microphone connections
  • Long cable runs, particularly in live venues where there’s lots of lights.

Thus, for instrumental devices, I wonder if there’s a real-world benefit that I’m missing altogether. Whenever I’d play live I would always run into either a DJ mixer, or a DI within 10feet, which would handle the balancing for the long-runs. Perhaps my lack of ‘seeing the light’ is due to the ubiquity of unbalanced connections in non-pro-audio gear, or perhaps there’s just no light to see.

Would love to hear your personal experiences where a balanced connection saved the day!

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I agree. It makes sense when you have long cables (10-20m or more) for various reasons. Then it solves many problems like you can’t have a common GND as return path, outside interference rejection etc.

calling @objectgroup for this

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Never heard of an instrument with balanced output. DI is the standard.

With regards to the benefits- common mode noise rejection can be useful in any situation where interference is an issue, cell phones, switching power supplies etc can create EMI/RFI. So if your cable is bundled with a mains cable or sitting on top of a wall wart or something this can be an issue, even in relatively short cable runs. The benefits of noise rejection become quite desirable if you’ve ever had to spend hours on end fucking with noise reduction algorithms to fix a piece of music that was recorded near an EMI source.

Its true though, most small home studios don’t need balanced audio. I’ve heard of mastering engineers using unbalanced audio with short-run high quality cabling, perhaps because balancing and unbalancing requires the audio to pass through either transformers or transistors (discrete or THAT chips), which can distort/saturate/color the audio. On the other hand some find these distortions, traditionally an incidental artifact of balancing audio to reduce noise in cable runs, useful for adding harmonic overtones or increasing the nominal level of their sounds. Many a gearslutz thread on this topic.

Jensen/Bill Whitlock has some nice detailed white papers on the technicalities balanced audio that are worth a google search.

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using a mixture of home-studio-type pro audio equipment and protoboard circuits at work for lab measurements. Periodically I measure the noise floor of the whole jerry-rig and try to improve it…

In my experience unbalanced cables typically will get you down to -90dBV or so in absence of nasties like stage lights in immediate vicinity of your setup (that means the noise is order some tens of microvolts).

I found the limiting factor for unbalanced is ground loops. So a ground loop results every time you connect two unbalanced devices whose signal ground is mains ground. The funny thing is, most balanced outputs/inputs/cables seem to be hooked up in such a way that the ground loop is not avoided. If you use a a TRS jack to connect two pieces of audio equipment, I found many times the screen of the cable creates a ground loop, totally defeating the object of using balanced cables…

Managed a 20dB improvement in my noisefloor last time I was playing this game by snipping the ground pin on the amp’s mains cord (EDIT: DON’T DO THIS). Probably would have been safer to unsolder the screen from one end of the TRS jack, mind you!

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I’ll say what I know from a “pro” standpoint. To the initial forum post, @Galapagoose, Every day balanced cabling has saved my life, or at least signal quality. You wouldn’t notice that the balanced cables are saving the day. They just do. They are what combat the noise from your instrument to the stagebox to the mixer 50 feet away, to the amps 50 feet away. From their the speaker lines are unbalanced. That is because their signal is so high, some noise will not be noticed. Mics are susceptible to noise because their signal level is so low. Without the balanced cabling most systems in most venues would be plagued with hum. I also thought I had heard the the high impedance of instrument outs helped stopped noise somehow. Either way, most newer keyboard have balanced line outs.

Balanced cables aren’t really necessary for the performer. Having XLR outs on gear might just be to make things easier to plug in on stage. You get rid of DI’s, which are another link in your signal chain that could go bad.

Even balanced outputs can have noise. In fact a lot of balanced circuits are done cheaply. A lot of di outs on amps are bad (because they are added in cheaply), even from familiar amp makers. There is a reason some DI’s are $250

Another example: I recently switched from normal TRS cables to quad (double balanced) cables. The difference in noise to my monitors was small. Most the noise comes from the quality in the amps and my screen. In effect balancing your whole system will do little for your sound quality if the rest of the gear isn’t crystal. You might not hear a difference in a home studio, but you might hear it in a super pro studio or PA.

I agree with all this. Except there are some instruments with balanced outputs. most are custom. There aren’t very many like that because of cost. And that it is not really needed. Just plug into a DI. Also balanced outputs require active circuitry, so everything would need batteries. Another practical reason most instrument outs are not balanced.

@rick_monster I would never recommend snipping a ground on mains. If you are talking about a guitar amp. The current can travel through your fingers and discharge to your new ground, your mic. That could potentially discharge 100 volts to your face!
Also stopping ground loops is not really what balanced cables are for. That’s what a ground lift does; like your snipped shield cable. Balanced systems are just a bit more resistant to ground loops. The loop was going to happen either way most likely. The choice of cabling doesn’t change much. http://www.soundonsound.com/sos/1994_articles/aug94/groundloops.html

This is news to me! I’m curious which manufacturers have decided this was necessary, or if perhaps it’s just a marketing term as it seems from this discussion that it’s generally considered unnecessary.

The funny thing about this is I’ve often been told by live sound engineers that I have to plug into the provided DI (usually $40 active behringer box), even when my gear is transformer balanced w/ groundlift option! As I understand, most DI boxes have unbalanced inputs, so negates any balancing on the instrument side.

This is a really interesting point, and I had a suspicion this was the case. I’d love to hear more about what quantifies a good vs bad balanced circuit. Both from the user & designer perspective. Is a ‘badly’ balanced connection worse than a good unbalanced one?

From the responses so far it seems that balancing is much more important on the ‘systems level’ when working with large setups. On one level this gives me confidence that synthesizers & other digital instruments don’t need to be balanced- they’re almost never going to be the weakest link. Conversely I worry that if everyone took this approach it would drive down overall signal integrity. Are instruments particularly well placed to be the unbalanced part in the chain?

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umm nope my reckless streak goes back in the box when valve amps with scary 500V DC lines come into the equation…

The amp that got the treatment was an alesis RA150. I’m certainly not reccomending anyone else try this - unsolder the screen on TRS jack instead to defeat the ground loop.

Thanks for breaking this out into its own thread. I’m also super interested in what other folks think about this, especially since I have somewhat limited real-world experience to draw on.

I’d definitely second the recommendation of reading some of Bill Whitlock’s writing on the matter, as that’s one of the things that triggered this discussion in the first place. Whitlock’s writing (and possibly some of Rod Elliott’s related discussion) do touch on the ground loop issues as well…

After a bit more reflection, and some research into the specs on the gear that I have now or have had in the past, it does indeed look like most prosumer-y things that I’ve encountered don’t actually have balanced outputs, but a surprising number of things do have balanced inputs.

Two questions stand out to me right now:

  1. How hot is the actual signal?
  2. What role does the device play in the overall system?

With microphones, the signal is usually pretty low voltage, and usually the balanced termination is followed by some pretty substantial gain, making the SNR of the channel extremely relevant to the noise floor, so having a balanced output connection seems of paramount importance.

With a synthesizer or other type of electronic instrument, you usually have a pretty reasonable output signal, and perhaps the assumption is that in professional environments, one would use a DI box before connecting to outboard gear, or a mixer, etc.

None of the synths or samplers that I have access to now, or have had access to in the past, have balanced outputs, but, interestingly, most of the line inputs in mixers I’ve seen are balanced. Even the line inputs on the cheap Behringer Xenyx series are balanced. (Though the outputs are unbalanced, of course ¯\_(ツ)_/¯)

This leads into the “role in the system” thought for me: you could use a mixer in the local context of a single person’s rig whose instruments all have unbalanced outputs, making the balanced-ness of the line inputs somewhat useless, or you could use it in the front of house, where you’re getting long-run balanced inputs from DI boxes on stage. Balanced inputs enable the same hardware to play both roles.

So, what’s the role of the device in question? Does it need to be flexible enough to use in a FOH-type situation (or, for example, a gallery installation) where balanced inputs would be helpful? Or is it instead reasonable to expect whoever’s using it in that situation will stick a local mixer in front of it to terminate any necessary balanced lines? Similarly, is it reasonable to expect that whoever’s using it will have DI boxes available to balance the outputs if/when needed?

Obviously these aren’t necessarily questions that warrant forum responses, but they seem to be relevant design thoughts.

The Whitlock writing touches on this a lot, but to summarize some of it: Balancing is effectively just matching the impedance of the two signal lines. What makes it good or bad is how closely the impedances are matched. Transformers do this very well inherently, and the THAT ICs do this well because they laser-etch the resistive substrate of each channel to match them. Doing this well in a discrete circuit is time consuming, since you’ll want to manually match your output resistors, and expensive, since you’ll need to buy lots of “high-precision” (although not high-enough precision) resistors so that you have enough choices to make the best matches.

From a user’s perspective, a “good” balanced circuit “just works”, doesn’t introduce noise, and/or doesn’t color the signal in undesirable ways. From a design perspective, you basically just want it to be cheap and simple enough to be economically practical, generally stable, and easy to troubleshoot (and possibly also small, if moving to 1/8" connectors is the thought).

From what I’ve read, it seems like the answer to this is “maybe”… My understanding is that an unbalanced connection in a high-noise environment just impart a higher noise floor (and possibly introduce artifacts, like audible clicking from your cell phone or wifi RF). A poorly balanced connection may color the signal or behave as a filter in an undesirable way. Which one of these is better than the other, I’m not really sure, and probably depends on the context.

@Galapagoose in response, in general. Yes, marketing is a thing. You put balanced outs on it and charge more money. you put very cheap circuits in that aren’t good and you make the most money. I have a book that is a bit bit over my head right now about building amps and mixers. It’s called the audiophile’s project source book. It goes into details about balancing circuits. It states that most pro gear that have balanced outputs, use a certain kind of opamp circuit. These are not the optimal circuits to use, but are mostly just good enough. The quality varies with the quality of components used as well. The ideal circuits are a few bucks more to implement and are more specialized.

Engineers might want you to go into a di for many reasons. To switch from a 1/4" to xlr… Their stagebox might only be xlr. All the venues I work at have only XLR inputs on stage and very few 1/4" to xlr turn arounds or cables. So a 1/4" balanced out is about as good as unbalanced to me on stage. In the studio, it’s different. They also coulb be trying to o generally reduce the signal you are outputting, or to throw a pad on as well. It can be good practice to always use one. Especially with DJ’s who tend to send hot signals, or synths which are unpredictable.

Yes a bad balanced output is a lot of times worse. I just use the unbalanced then and throw a DI on it. there are a lot of components that make up that output, a badly balanced circuit might not be what is making the noise.

It is mostly systems level. Instruments don’t need to be balanced. They are in a good place not to. But you instrument is 95% the weakest link in the chain in general when it comes to tech in most pro venues. Balanced signals usually don’t solve most problems.

timely thread as i’m just in the middle of recabling the studio, using the opportunity to do everything ‘properly’ this time, so going with balanced connections wherever they are supported. everything is within a short distance but i assumed it would help fight any possible interference from power bricks and computer, but the main reason was to avoid any potential weirdness when connecting balanced inputs/outputs using unbalanced cables, as well as avoid potential gain issues. but sounds like it’s not necessary after all?

also, does having everything go through balanced patchbays change anything? or is unbalanced still okay in this case?

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Yes. You can patch unbalanced signal through balanced patchbays. One of the wires just isn’t used.

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most stage piano manufacturers provide balanced outs on their keyboards: yamaha, roland, kurzweil, etc. many of them include both TRS and XLR connections in the unit; my yamaha CP5 has both types of balanced output.

a notable exception to the pattern is nord. their keyboards seem to all be unbalanced–and i generally see more nords used than anything else onstage, including big church venues. possibly the cable runs are shorter at locations where they’re more or less permanently plugged in at a designated point.

I think XLR connections, whilst bulky, are super nice & very rugged. Plus they’re pretty ubiquitous and massively available at every venue - good luck finding a 1/4" cable lying around a venue that isn’t in terrible shape. Perhaps, regardless of balancing, that’s a good reason to include XLRs on physically larger devices where panel real estate / form factor isn’t as much a limiting factor.

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As @Tyelr said, if your lines are unbalanced and your patchbay is balanced, you’ll be fine.

I read your question the other way though: balanced lines through an unbalanced patchbay is not a good idea.

thank you for clarification! yeah, i meant connecting devices with unbalanced inputs/outputs to a balanced patchbay.

and this is what 140+ unconnected cables look like - thankfully all connected now, just need to test and hope i don’t have to take it apart again any time soon…

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looks like a fun way to spend your afternoon! :smile:

it would be if my back didn’t decide to cripple me the day before… afternoon is too optimistic though! took 3 days off work to do this - but that and a sore back was worth being able to run 8 inputs/outputs between eurorack and patchbays!

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woah

yes indeed…that sounds awesome

fun fact: my dad cuts the ground plug off of all his power strips etc!

safety vs hum reduction…

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