Balanced vs Unbalanced

[cincy_kid]

So in my quest to better understand how signal paths are important I have been reading various threads about balanced and unbalanced lines. Although I understand the difference in the 2 (unbalanced having a "hot" and ground, where the balanced has an extra signal, a "cold" or neutral).

Also, I know that balanced lines are much more important when running long cables for low noise stuff such as microphones but my question is specifically about my rack.

for example, on my Tampa mic pre, it has a balanced 1/4" output that I run a TRS cable from into my Delta 1010 input (which accepts balanced or unbalanced).

Now, on my ART TPS pre, the 1/4" out is unbalanced, but also has a balanced XLR out. With a short distance of cable, does it matter which out I use? Will it affect the quality of my recordings? Is it worth getting an XLR to TRS cable for this purpose?

Same question for the outs of my soundcard. My current setup has the outs of my soundcard running into a channel into my mixer (mainly so I can run headphones from the mixer when I am recording so I can hear the rest of the mix and then I also have the main outs of the mixer going to my monitors when I am doing my editing/mixing). So does it matter if I use TRS or TS cables from the sound card to the mixer?

hope this makes sense, thanks!

 

[moresound]

No matter what ... I always go with the balance line when ever possible.

 

[cincy_kid]

I guess that's a pretty good rule to follow

So there is no quality loss using an XLR to TRS cable since they are both balanced?

 

[Chili]

I guess that's a pretty good rule to follow

So there is no quality loss using an XLR to TRS cable since they are both balanced?

Nope, not for your intentions. The magic of a balanced cable is the cable itself. Two wires are twisted together and wrapped inside the third which is a foil or braided shield. There is a science to how tight the twisted pair are twisted. That's where the quality is noticed.

As a side note; you never want to use that kind of cable where phantom power is being used. But in your case, not a problem.

 

[snow lizard]

As a side note; you never want to use that kind of cable where phantom power is being used. But in your case, not a problem.

Phantom power works fine with TRS as long as it's wired correctly, but the practice is to make all the cable connections before applying power. If you hot plug an XLR ribbon mic into a console that already has phantom applied it probably won't do too much. All the pins will connect at roughly the same time so the transformer in the mic should block the power from getting to the ribbon. If you do the same thing with a TRS patch bay it will cause a momentary "pop" where the ribbon can get stretched and damaged from the power jolt.

Either way if you make the connections before applying power everything should be okay. If the ribbon mic doesn't need phantom and you have the option to not use it, it's not an issue.

And yeah, in the OP's case there wouldn't be any phantom in that kind of connection.

 

[snow lizard]

Now, on my ART TPS pre, the 1/4" out is unbalanced, but also has a balanced XLR out. With a short distance of cable, does it matter which out I use? Will it affect the quality of my recordings? Is it worth getting an XLR to TRS cable for this purpose?

If it's a short cable run there won't be any quality loss from interference signals getting into the cable. There might be a loss of signal by around - 3 or 6 dB? I forget. Basically the balanced line has 2 conductors carrying signal whereas the unbalanced line has one. So balanced lines carry twice as much signal. Whether or not the unit you have compensates for that is another issue.

I'd say it's not a big deal if you're using a short run.

Also XLR to XLR vs. XLR to TRS balanced cables operate the same way. There shouldn't be a difference in quality, only the type of connector.

 

[Bobbsy]

Phantom power works fine with TRS as long as it's wired correctly, but the practice is to make all the cable connections before applying power. If you hot plug an XLR ribbon mic into a console that already has phantom applied it probably won't do too much. All the pins will connect at roughly the same time so the transformer in the mic should block the power from getting to the ribbon. If you do the same thing with a TRS patch bay it will cause a momentary "pop" where the ribbon can get stretched and damaged from the power jolt.

Either way if you make the connections before applying power everything should be okay. If the ribbon mic doesn't need phantom and you have the option to not use it, it's not an issue.

And yeah, in the OP's case there wouldn't be any phantom in that kind of connection.

I'd make a point of NEVER running phantom power via a TRS cable or any form of patch field using jacks.

Because of the way the TRS makes each leg at a separate time, you can have 48 volts running though pieces of gear simply not designed for it. A loud pop is the lucky outcome. If you're less lucky, some permanent damage can result. For this reason, I've always been scrupulous about doing any mic level patching with special XLR panels.

 

[Bobbsy]

If it's a short cable run there won't be any quality loss from interference signals getting into the cable. There might be a loss of signal by around - 3 or 6 dB? I forget. Basically the balanced line has 2 conductors carrying signal whereas the unbalanced line has one. So balanced lines carry twice as much signal. Whether or not the unit you have compensates for that is another issue.

I'd say it's not a big deal if you're using a short run.

Also XLR to XLR vs. XLR to TRS balanced cables operate the same way. There shouldn't be a difference in quality, only the type of connector.

NO!

A balanced line doesn't double the signal level--or at least that's a minor by-product.. The way balanced circuitry works is that the signal is fed in inverted phase between the two conductors. Then, in the balancing/unbalancing circuitry, one leg is phase inverted, causing any noise that's been induced in the cable run to cancel itself out.

It's true to say that, over short runs, you can generally get away with unbalanced feeds, particularly if you use decent quality screened cable. However, that's not a guarantee and even a couple of feet of unbalanced running past something like an arcing thermostat can pick up noise. As others have said, use balanced wherever possible.

 

[cincy_kid]

Thanks for the replies guys, and just so I am clear.

I will be using Phantom power when plugging the mic into the front of the pre using an XLR to XLR. But it the back of the pre from the output to the input of the soundcard, I plan to get an XLR to TRS cable. It's ok to use Phantom power on the front when using this configuration correct?

 

[Chili]

Thanks for the replies guys, and just so I am clear.

I will be using Phantom power when plugging the mic into the front of the pre using an XLR to XLR. But it the back of the pre from the output to the input of the soundcard, I plan to get an XLR to TRS cable. It's ok to use Phantom power on the front when using this configuration correct?

Just to be clear, YES!! Your plan is a good one.

 

[snow lizard]

I'd make a point of NEVER running phantom power via a TRS cable or any form of patch field using jacks.

Because of the way the TRS makes each leg at a separate time, you can have 48 volts running though pieces of gear simply not designed for it. A loud pop is the lucky outcome. If you're less lucky, some permanent damage can result. For this reason, I've always been scrupulous about doing any mic level patching with special XLR panels.

Which comes back to the point of making cable connections before turning the power on.

For home recordists it's not likely to be an issue in most cases. If you want to build a studio with a huge live room and put a massive Amek or something in the control room a lot of people will build mic inputs into the walls of the live room to keep cable routing from turning into the spaghetti monster. A patch bay will allow you to run any line into any channel. Could be done with XLR. Or TRS.

A balanced line doesn't double the signal level--or at least that's a minor by-product..

It's a minor byproduct. From the output of a preamp I'd expect it to not be an issue, but if you pull the transformer out of an SM57 it is.

The way balanced circuitry works is that the signal is fed in inverted phase between the two conductors. Then, in the balancing/unbalancing circuitry, one leg is phase inverted, causing any noise that's been induced in the cable run to cancel itself out.

Yup. Because the conductors in the balanced line are a twisted pair, any noise that gets induced in one side is pretty much duplicated in the other - and cancelled very effectively when the signal is unbalanced.

It's true to say that, over short runs, you can generally get away with unbalanced feeds, particularly if you use decent quality screened cable. However, that's not a guarantee and even a couple of feet of unbalanced running past something like an arcing thermostat can pick up noise. As others have said, use balanced wherever possible.

It's a good point to consider. I'm sure there are a lot of people who stay balanced when they can with no ill effects.

Another one I've seen is that signal processing gear doesn't work on balanced signals. It makes perfect sense to use balanced cables for mics because in extreme cases they might have to go through some 60-70 dB amplification to come up to line level. If there's any noise it's going to be amplified. Once you're at line level the process of balancing a signal to go to the next stage is an extra process that's going to be undone as soon as it gets there. Some people figure this extra stage can colour the sound, and it's safe enough to avoid if you're only doing small runs.

I don't think I've seen a guitar with balanced output.

Again, if there's people pulling the trannies out of 57's, the output drops and the S/N ratio of the mic gets worse. Doesn't sound like a good plan when you look at it that way. But the frequency response of the mic gets wider and flatter. The top end opens up. The tranny does the balancing act but it also chokes the output of the cartridge. So you have options. You can live with the stock performance of the mic, pull the tranny and run it that way, upgrade the tranny to something better or use a different mic that doesn't have these problems.

Much like balanced vs. unbalanced it comes down to weighing the alternatives and choosing your own preference.

 

[snow lizard]

Thanks for the replies guys, and just so I am clear.

I will be using Phantom power when plugging the mic into the front of the pre using an XLR to XLR. But it the back of the pre from the output to the input of the soundcard, I plan to get an XLR to TRS cable. It's ok to use Phantom power on the front when using this configuration correct?

Absolutely not a problem.

 

[Bobbsy]

Which comes back to the point of making cable connections before turning the power on.

For home recordists it's not likely to be an issue in most cases. If you want to build a studio with a huge live room and put a massive Amek or something in the control room a lot of people will build mic inputs into the walls of the live room to keep cable routing from turning into the spaghetti monster. A patch bay will allow you to run any line into any channel. Could be done with XLR. Or TRS.

We had a hard and fast rule. Line level patching was done with jacks (B gauge ones to be specific) but all mic level patching was done with XLRs.

It's a good point to consider. I'm sure there are a lot of people who stay balanced when they can with no ill effects.

This would apply to any professional grade studio. There's little or no unbalanced gear once you get beyond consumer grade.

Another one I've seen is that signal processing gear doesn't work on balanced signals. It makes perfect sense to use balanced cables for mics because in extreme cases they might have to go through some 60-70 dB amplification to come up to line level. If there's any noise it's going to be amplified. Once you're at line level the process of balancing a signal to go to the next stage is an extra process that's going to be undone as soon as it gets there. Some people figure this extra stage can colour the sound, and it's safe enough to avoid if you're only doing small runs.

Are you actually recommending the avoidance of of balanced gear because it somehow colours the sound? With the exception of a small amount of "boutique" gear that occasional producers might bring in, every commercial recording you listen to (be it a CD, Film or TV programm) is done pretty much exclusively on balanced gear

I don't think I've seen a guitar with balanced output.

Different situation. Guitar outputs are high impedance and at a level roughly halfway between mic and line level. Still, they COULD be balanced but there's just too much legacy gear out there.

Again, if there's people pulling the trannies out of 57's, the output drops and the S/N ratio of the mic gets worse. Doesn't sound like a good plan when you look at it that way. But the frequency response of the mic gets wider and flatter. The top end opens up. The tranny does the balancing act but it also chokes the output of the cartridge. So you have options. You can live with the stock performance of the mic, pull the tranny and run it that way, upgrade the tranny to something better or use a different mic that doesn't have these problems.

Much like balanced vs. unbalanced it comes down to weighing the alternatives and choosing your own preference.

There's only one clear answer: use a mic that gives you the frequency response you need without degrading other areas of performance.

The same goes for balanced vs. unbalanced. If balanced is available, use it.

 

[MCI2424]

Minor correction:
"...Then, in the balancing/unbalancing circuitry, one leg is phase inverted, causing any COMMON MODE
noise that's been induced in the cable run to cancel itself out....."

 

[Lt. Bob]

I'd make a point of NEVER running phantom power via a TRS cable or any form of patch field using jacks.

Because of the way the TRS makes each leg at a separate time, you can have 48 volts running though pieces of gear simply not designed for it. A loud pop is the lucky outcome. If you're less lucky, some permanent damage can result. For this reason, I've always been scrupulous about doing any mic level patching with special XLR panels.

I've also read that even the proper cables really shouldn't be plugged in or unplugged while the phantom is on as this can possibly damage the channel strip and/or possibly the tranny for that mic pre. True?

Anyway ..... I always make sure phantom is off before doing any patching or cord plugging of any sort around the mic pres.

 

[ashcat_lt]

So in my quest to better understand how signal paths are important I have been reading various threads about balanced and unbalanced lines. Although I understand the difference in the 2 (unbalanced having a "hot" and ground, where the balanced has an extra signal, a "cold" or neutral).!

This is incorrect. It's minor, it's common, but it reflects a fundamental misunderstanding.

The two conductors in an unbalanced cable are, in fact, but signal carrying wires. Sometimes one is more positive, and sometimes the other, and therefore neither can really be called "hot". Neither can you really call either one "ground". Yes, one of the conductors usually is a braided shield, and is usually connected to chassis ground at both ends, but it doesn't have to be. Its better to call them "inner conductor" and "shield" or "tip" and "sleeve" or maybe "signal send" and "signal return".

The signal in these wires are, in fact, inverse of one another - exactly like those in the two inner conductors of a balanced cable, though sometimes derived differently. In many situations you can connect an unbalanced output to a balanced input via a "psuedo-balanced" connection to get most of the benefits of balanced. This involves a custom cable - two conductor plus shield. On one end a TS plug has each of the contacts connected to one of the inner conductors, and the cable shield not connected. The other end has a TRS connected as normal so that you get Tip>Tip, Sleeve>Ring, and the shield braid connected only to the Sleeve on the balanced end. It may not be worth the trouble for short runs, but it can work. Has the benefit of breaking ground loops sometimes, too.

 

[bouldersoundguy]

There's only one clear answer: use a mic that gives you the frequency response you need without degrading other areas of performance.

Like an SM77.

 

[snow lizard]

Are you actually recommending the avoidance of of balanced gear because it somehow colours the sound?

Not really. I'm saying if you have gear that lets you do it either way you could try it both ways and do what you like. Either way is valid if it works. Balancing becomes necessary over longer cable runs.

For my own setup I have a 16 channel board with a 4 channel tape out subgroup. XLR balanced output. The interface is 4 channels, TRS balanced or unbalanced. So I bought 4 15 ft. mic cables and 8 TRS plugs, cut the cables in half and started soldering. When connected this way, the noise floor hovers around where the spec for the board says it should be. It's quiet enough that I can live with it so this is what I usually do.

I can also take a guitar cable and run a line from the "first click" of the insert on each channel. It makes the noise floor go down by around 10 dB, but the line isn't balanced. By doing this I have a minimal signal path that takes a lot of components out of the routing. Granted it's taking a lot more out of the chain than just a transformer or what have you to balance the signal, but not being balanced over a short cable run (15 or 20 ft. in this case) isn't a deal breaker. Cable noise doesn't seem to be an issue.

Minimal path vs. cables that don't pick up noise. Which do you prefer? Is there a substantial difference either way?

 

[PRHunt]

The "balance" in a balanced connection does not rely on having inverted signals running in each conductor, but rather on each conductor having equal impedance to ground. The better the match, the higher the rejection of common mode noise (CMRR).

"Better" mic preamps will use 0.1% tolerance or better resistors (including the 6.81K ohm phantom resistors) at their inputs to improve common mode noise rejection.

The aspect of having equal and inverted signals is referred to as differential, and it is differential signals that provide the +6dB boost when received and converted to single ended. But differential transmission is not a prerequisite for balanced signals (at least not for audio).

A practical consideration is that you can fairly easily modify equipment which has unbalanced output to have true balanced outputs with the addition of as little as a single resistor and a trs socket.

Reference: http://www.jensen-transformers.com/an/an003.pdf