XLR Balanced Cables

[jheis]

I recently bought a B&K Ref 50 pre-amp/processor and a pair of B&K ST125.2 amps which have "XLR balanced inputs/outputs" What, if any, is the difference between these cables and good quality RCA cables.

I've always considered "esoteric cables" to be a rip-off. Is XLR "more of the same" or are they worth the extra bucks?

I'm asking because I don't know.

James

[djk]

Balanced cables, if done correctly, are great.

Having said this, most are not done correctly.

I have used unbalanced cables about 125ft long with no problems.

If you have 'problems' and think you need balanced inputs, go lay down for a while, then use a 10K:10K isolation transformer with unbalanced lines. Jensen is a good brand.

[DrWho]

An XLR cable is a term used for a "2 conductor with shield" cable that has the XLR tips (aka mic cable). An XLR cable is most often used for carrying a balanced signal. In a balanced configuration, the 2 conductors are carrying the same signal and then the shield is used for the ground.

The main advantage of a balanced connection is that it reduces noise by reversing the phase on one of the 2 conductors. The signal travels down the cable where EMF is being picked up equally on both wires. When the signal gets to it's destination the phase is unreversed; effectively eliminating all the noise because the noise is now out of phase and then summed.

A balanced XLR connection is also capapble of running longer distances, say a couple miles. An unbalanced connection can only run about 300 feet max (depending on the specific wire being used, this figure can change).

Also, I feel that the XLR tips are a much better way of connecting anything. They lock into position and don't suffer as much from cable damage from being bent.

There is no disadvantage to using an XLR cable. So why then isn't everything XLR? Because it's more expensive. For what it's worth, you will see no professional gear without XLR connections (or balanced 1/4") because the pro's don't want to deal with the problems associated with unbalanced. In a home situation, the advantages that XLR cables offer are generally not as important and thus it's a "pointless" expense.

[meuge]

Balanced connections do a very good job of dropping the noise floor. And the cool thing is that you don't need very expensive ones. I would bet that a set of cheap Pro XLR cables will have better electrical characteristics than 90% of the uber expensive esoteric cables out there.

[djk]

Both of you guys missed the point.

Cheap balanced inputs degrade the sound.

You are better off unbalanced unless you have a real problem.

CMRR is a red herring, the real problem is galvanic isolation, and only a transformer can do it.

A balanced input with 1% resistors that are worst case (but still in spec) will only have 24dB CMRR. If you hand select the resistors to 0.1% you may be able to get 60dB CMRR.

Worst case with a transformer and unbalanced lines will be 70dB.

In any event the limiting factor in balanced lines is how uniform the twist on the wire is. Belden, one of the best, can only do it to 60dB. Cheaper wire is always worse.

A real piece of pro gear has an octal socket on the back. For your transformer. Studio needs may change and gear goes through the buy/sell/trade cycle, but you always keep your transformers to plug into the new piece. Since they are a one time purchase you try and buy the best you can afford.

[DrWho]

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On 11/6/2004 6:36:59 AM djk wrote:

Both of you guys missed the point.

Cheap balanced inputs degrade the sound.

You are better off unbalanced unless you have a real problem.

CMRR is a red herring, the real problem is galvanic isolation, and only a transformer can do it.

A balanced input with 1% resistors that are worst case (but still in spec) will only have 24dB CMRR. If you hand select the resistors to 0.1% you may be able to get 60dB CMRR.

Worst case with a transformer and unbalanced lines will be 70dB.

In any event the limiting factor in balanced lines is how uniform the twist on the wire is. Belden, one of the best, can only do it to 60dB. Cheaper wire is always worse.

A real piece of pro gear has an octal socket on the back. For your transformer. Studio needs may change and gear goes through the buy/sell/trade cycle, but you always keep your transformers to plug into the new piece. Since they are a one time purchase you try and buy the best you can afford.

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You talking inputs or the cable itself? Last I checked, there were no resistors in my cables. Also, wouldn't you get up to 60dB more CMRR when using transformers on a balanced line versus an unbalanced one?

Unless I'm interpreting things wrong (you're using a few terms I've not heard before), it sounds like you're minimizing the advantages of balanced lines which contradicts a lot of what I've read and experienced first hand. If you've got links or resources handy, I'd very much like to read about what you're talking about (and perhaps go experiment myself).

Unbalanced vs. balanced lines

[djk]

The resistors are inside the equipment and are part of the circuit that receives the balanced signal.

They discuss this (and more) at the Rowland Research and Jensen websites.

The biggest lie in pro audio is the opamp + four 1% resistors used to make a balanced input. It costs virtually nothing, and that's whay you find it on every cheap EQ, amp, crossover, etc.

It also does virtually nothing, and thereby the poor soul that has a real problem that could be solved by a transformer thinks: I've already tried balanced.

[Jim E]

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On 11/5/2004 1:53:06 AM jheis wrote:

I recently bought a B&K Ref 50 pre-amp/processor and a pair of B&K ST125.2 amps which have "XLR balanced inputs/outputs" What, if any, is the difference between these cables and good quality RCA cables.

I've always considered "esoteric cables" to be a rip-off. Is XLR "more of the same" or are they worth the extra bucks?

I'm asking because I don't know.

James

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XLR is a great way to connect equipment if you have balanced line components. If you can solder, custom length cables are a snap. Belden, Canaire and Mogami make excellent cable for this application for well under two dollars per foot. I use Neutric XLR connectors which run three to four bucks each. If you compare that to the cost of "good quality" RCA's the cost is reasonable. As far as XLR's being "esoteric" I would have to say no, they are not. In pro use XLR connections are the standard. One thing to keep in mind though, most balanced equipment is setup to function best (lowest noise) at either 0 dB or +4 dB at 50% modulation. This level is significantly higher that consumer unbalanced equipment. Also, connecting unbalanced audio to balanced can be difficult.

Are unbalanced connections available for the inputs on the pre-amp for your line sources?

[jheis]

Jim:

The B&K Ref. 50 pre-amp has XLR outputs (along with RCA's) and the B&K ST125.2 amps have XLR inputs (along with RCA's).

I stopped by "Good Guys" the other day to pick up a digital coax cable and they had four "open box" Monster Cable Z200IX XLR cables marked down to $65 so I bought them (sounds like rolling your own is considerably cheaper). I figure if the equipment is designed for XLR, I might as well optimize what I've got.

The Ref. 50 has two sets of balanced inputs for CD & DVD, but none of my line sources have balanced outputs. So, the only place I'm using the XLR balanced cables is from the pre-amp to the front and surround amps. My rear & center channel amps do not have XLR inputs, so I'm using Monster Cable RCA interconnects.

I have a partial hearing loss in my right ear, so I doubt that I can actually distinquish incremental changes. So, as long as it sounds good, I'm happy.

James

[Jim E]

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On 11/7/2004 10:56:05 AM jheis wrote:

Jim:

The B&K Ref. 50 pre-amp has XLR outputs (along with RCA's) and the B&K ST125.2 amps have XLR inputs (along with RCA's).

I stopped by "Good Guys" the other day to pick up a digital coax cable and they had four "open box" Monster Cable Z200IX XLR cables marked down to $65 so I bought them (sounds like rolling your own is considerably cheaper). I figure if the equipment is designed for XLR, I might as well optimize what I've got.

The Ref. 50 has two sets of balanced inputs for CD & DVD, but none of my line sources have balanced outputs. So, the only place I'm using the XLR balanced cables is from the pre-amp to the front and surround amps. My rear & center channel amps do not have XLR inputs, so I'm using Monster Cable RCA interconnects.

I have a partial hearing loss in my right ear, so I doubt that I can actually distinquish incremental changes. So, as long as it sounds good, I'm happy.

James

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James,

Then I would use the balanced connections from the pre-amp to the amp inputs.

I am not a fan of these high end cable manufacturers. While most the cables are good to be sure, I have never been able to justify the cost of these so called "premium esoteric cables". I have not been able to measure (much less hear) a difference.

A well built cable does not have to cost an arm and a leg.

[DrWho]

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On 11/7/2004 3:27:54 AM djk wrote:

The resistors are inside the equipment and are part of the circuit that receives the balanced signal.

They discuss this (and more) at the Rowland Research and Jensen websites.

The biggest lie in pro audio is the opamp + four 1% resistors used to make a balanced input. It costs virtually nothing, and that's whay you find it on every cheap EQ, amp, crossover, etc.

It also does virtually nothing, and thereby the poor soul that has a real problem that could be solved by a transformer thinks: I've already tried balanced.

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I did do a lot of reading (on another pc so i dont' have any links readily available) and I was surprised at what I found. Is there any way to easily determine what kind of circuitry your components have without tearing them apart? I only ask because I know of a permanent install that has been having issues with noise getting onto the signal lines running between the booth downstairs and the amps upstairs...One of the local crappy sound companies put a transformer on to help, but then this introduced a buzz and then they added another transformer to fix that and then they added a few more "just in case" and I've always felt that there had to be a better way (and I had no clue how a balanced line had so much noise). Now after getting into the reading I wanna smack this company even more (this same company decided it was ok to switch out the amps after the dress rehearsal when I had already dialed everything in to an amazing sound and then they claimed that no EQ changes would be necesary with the new amps...also, in the process they managed to blow all the subs, but I felt that it was an EQ issue. let's just say it was a rough concert.)

Anyways you obviously know your stuff, djk...I hope you didn't take offense to my doubts as I felt that I should have at least come across these concepts in the many years I've been "in the business". There's so much crap floating around the audio industry that it's just natural to not believe anything new. Thanks for the tip, I'm gonna have many hours of new reading ahead of me.

[kjohnsonhp]

As I too am shopping for cables for my pre/pro and MC amp with both XLR and RCA options available I've found:

1) DIY both cables can be high performance and affordable

2) XLR for this appliation (ie <1m length) isn't necessarily better (other than the physical connetion difference which was explained earlier) and especially since in my case the pre/pro & MC aren't a true balanced system.

3) Blue jeans cables has some reasonably priced XLR cables (Belden, etc.)

4) I'm skeptical that I could hear a difference between nice Belden RCA interconnect at under $100 for 5 vs similar quality XLR connections around $200 for 5.

[WMcD]

Indeed the use of XLR balanced line connectors is not hype. As pointed out, they are used in professional equipment and have great immunity to noise and ground loops.

OTOH, as I've said before, you can't solve a problem which does not exist in the first place. RCA's do just fine in most applications.

Gil

[Erik Mandaville]

I've found that kitchen scales work very well for this! Just weigh the length of cable needed for one channel, and cut-to-length another piece within (+) or (-) 10% of the first piece. They should weigh just about the same, which would mean the two lengths would be equal and would balance correctly on a balance scale. I've done this with my own cables and they weigh almost exactly the same. They're thus just about perfectly balanced!

[Griffinator]

The XLR cable design is far superior to balanced 1/4" or unbalanced RCA - so much so that the fast majority of studios not only use it for long analog connections, but also for their digital transfers (AES/EBU spec) because this digital pass specification can handle far greater bandwidth (up to 8 channels at 24/384, compared to SPDIF at 2 x 24/96 or ADAT at 8 x 24/48 or 4 x 24/92 - all uncompressed transfer) with virtually no jitter, even in extremely long wire runs.

Will it improve your hifi? If you have XLR on both sides, then yes. If you have to introduce a transformer to convert unbalanced RCA to XLR, then probably not, because the transformer itself will alter the signal, thus negating the potential benefits...

[Parrot]

James,

In a home, there is virtually no chance using XLR cables will improve anything. They are nice for impressing people, but that's about it.

Further: Some equipment that has balanced outputs isn't really balanced internally. Again, in this case it would be for show, to look impressive.

I also doubt if any good can come from having some balanced equipment mixed in with some other unbalanced equipment.

[Marvel]

As Dennis pointed out, most equipment that has balanced i/o uses electronically balanced circuits, not transformer balanced circuits. Good transformers will not degrade your signal quality. Equipment with a Cannon/Switchcraft/Neutrik 3 pin connector is better for mainly two reasons -- the connectors latch in place and the pin to socket electrical contact is better.

Gil is right that for most folks an rca is more than adequate.

[formica]

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On 11/5/2004 3:51:04 AM djk wrote:

I have used unbalanced cables about 125ft long with no problems.

If you have 'problems' and think you need balanced inputs, go lay down for a while, then use a 10K:10K isolation transformer with unbalanced lines. Jensen is a good brand.

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Would the transformer go after (in the signal path of) the questionable long cable? I visited the Jensen site as well... interesting stuff... but not an inexpensive solution.

I ran into a RFI / EMI interference problem with some temporary test equipment I set-up at home. The noise was a constant hum... which did resemble a 60Hz tone. The PC I was using was in another room and needed about 30ft of unbalanced interconnect.

I tried several things with no improvement, and these included:

- I did run a power-cord from the PC back to the same outlet as the equipment to avoid a ground loop.

- I disconnected the interconnect from the PC (it was basically a 30ft wire plugged into the preamp input... that still hummed

- Moved the cable around to different locations incase it was getting EMI from wiring below the floor.

- I tried several different cables (plugged just in the preamp)... a heavy but "no-name" sub cable, a cheap 2$ "comes free with your equipment" cable, a DIY Belden cable with Neutrik connectors, etc... all in 30ft lengths with the same result.

The weird thing is i tried a shorter ±20ft cheap 2$ "comes free with your equipment" cable... and it DIDN'T hum. Either it's a better wire or it's acting like an antenna picking up RFI, since the length seems important.

Given this is a temporary setup... I was wondering what other more econonical solutions there might be. I already own a USB soundcard... would getting a long USB cable and shorter RCA help? I'd obviously still have to deal with groundloop precautions...

A compatible portable on battery power would be the best thing, but... not the cheapest. The one we have at home does not have a duplex soundcard and it doesn't support a USB soundcard.

Later...

Rob