XLR/RCA connections and distance question

[Coytee]

As I understand it, you can take an XLR line and run it essentially hundreds of feet with no noise pickup and evidently little if any, signal loss.

If that's inaccurate using 'hundreds' of feet, then this is for the home where we're talking 50'. I also understand that you don't really want to use an RCA line for say, a 50' run.

By the time I snake up a wall, down the length of the room around some ductwork and down the other wall, I'll have a length of say, 50'. I'm currently running BOTH regular speaker wire (so I can simply plug speakers into outlet) and some XLR wires so I can have an XLR outlet there if I ever want to move an amp to that side of the room.

Here's the thrust of my question... if this XLR length from Dx38 output across the room to the wall outlet is 50', could I then plug a XLR/RCA adapter there and plug a RCA amp into this signal path or would I be best served keeping it an XLR input amp? Would the distance that would work for an XLR line, also work against an RCA?

To make this more dramatic... could you do this after the 'hundreds of feet' that might be used at a concert? (if it would work there, it would work in the home...if it would NOT work there, then how do you figure out the distance where it goes from work to fail?)

[Marvel]

Staying balanced can get you hundreds of feet with a clear signal. My Alesis amps are balanced, butuse 1/4 in. stereo jacks.

Switching to unbalanced on the other end would possibly mess you up depending on:

how do you swothc to unbalnaced. an adapter that shorts the two leads together won't be helping you much. Using a high quality transformer would work ok, but that will cost some buck. Here is a situation where you get what you pay for. You might be able to get by with unbalanced the whole way.

Bruce

[Coytee]

Doing so loses the reason to have a balanced line

I'm not doing it so much for concerns on noise as much as, if I ever put an amp next to the speakers, if the amp is an XLR input amp, I want an XLR line there for simple compability to the Dx38 output.

you may be fine with a 50' unbalanced line

I must say, I thought the recommended maximums for unbalanced lines was something like 10'. I thought anything longer (maybe 15') was to be specifically avoided. That's good to know, I WILL give it a try!!

[mark1101]

Richard,

I am running unbalanced RCAs from my PC sound card into the Peach 25' with no issues at all. I am doing the same from a DVD player output into the Peach with 25' RCAs. Both are very quiet, and seem to have plenty of signal. Haven't tried further than 25'.

[DrWho]

The most I've gotten away with an unblanced line was 100 feet, but I got lucky. With a balanced line, I've gone over a quarter mile (probably closer to half now that I think about it). The guideline for 10ft or whatever is probably a distance that "no noise" can be guaranteed. Getting away with longer just means there is less noise in the environment.

Btw, if you're running cable in your wall, make sure you keep it away from power cords and the like...if you gotta come close, then it's best to cross at a right angle. Going to metal conduit usually doesn't help much because most of the interference will be magnetic in nature....using a magnetic material for the conduit will help though.

[mark1101]

Richard, you can run speaker wires 50ft. Right now I am using exactly 50' of speaker wire to each of my passives. Works fine.

[Islander]

With my previous room setup, I ran about 25 feet of unbalanced/RCA interconnect from my turntable to the receiver, bundled with speaker cables, with no noise issues at all. It was Wireworld Luna 5 interconnect, if that helps at all.

[djk]

Re: XLR cables can go how far? 09-09-2007

I've run unbalanced cables 135' with no noise at all. The cable was terminated with a 2.2K resistor at the far end (this reduced noise by over 10dB).

Sheffield Labs made 'the King James version' with a stereo mic feeding balanced cables 3/4 of a mile long.

Re: Balanced cable question (s?) 07-22-2006

I have run unbalanced lines in excess of 100 ft with 113dB/W HF horns and had no hum, and no noise.

Jensen has some good tutorials on the subject.

To summarize:

An unbalanced line with a transformer at the amp end worst case can still be 50dB quieter than electronically balanced equipment under the same worst case conditions. Most gear on the market is electronically balanced, this adds noise and distortion from the extra circuitry, and can cause a loss of clarity compared to an unbalanced system that is properly terminated. Electronically balanced equipment is much poorer at RFI rejection than transformer balanced equipment.

I have designed and built professional equipment.

One model of subwoofer amplifier I designed had balanced inputs with a low frequency CMRR pot, and a high frequency CMRR cap. Even adjusted on the bench for 100dB CMRR, there was still noise in the field. An octal socket was added on the back for a transformer. The user provides the transformer that best suits his needs and budget. No more noise.

A transformer is only needed at one end. The receiving end transformer is usually less expensive than the sending end transformer. Balanced and unbalanced gear may connected at random, as long as you remember the gain changes by ±6dB depending on which direction you're going.

Jensen may be the best, CineMag may be almost as good for a lot less, Edcor is 90% as good for only 10% of the cost. I buy singles of the $130 (new price) models on eBay used for $15 or so, and stereo Edcor new for $25.

Also read the notes on transformers at the Jeff Roland Design Group site.

Re: XLR Balanced Cables 11-05-2004

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.

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.

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.

[Don Richard]

The higher the impedance of the equipment that you are working with, the less you should be inclined to use unbalanced lines. While you may not have problems with noise, high frequency rolloff would be an issue. There will be more HF rolloff with higher impedance equipment. The line impedance is determined by the source impedance. Tube gear generally has higher output impedances than SS.

Modern servo-balanced equipment offers both low noise and high CMRR, mostly because of the use of modern op-amps especially designed for audio use. Transformers have their own set of problems, but they are hard to beat for killing ground loop issues, often a source of audible noise.

[TNRabbit]

The manual with my BenchMark DAC-1 states "avoid using RCA/unbalanced connections longer than 1370 feet, as some issues with impedance can arise"....!!!!

[philipbarrett]

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.

Cheap! I wish it was only that way, the list of pro gear incorporating a true transformer balanced input or output stage gets shorter daily. Shame too, there's nothing like a Jensen between you & the goods.

[djk]

"The higher the impedance of the equipment that you are working with, the less you should be inclined to use unbalanced lines. While you may not have problems with noise, high frequency rolloff would be an issue. There will be more HF rolloff with higher impedance equipment. The line impedance is determined by the source impedance. Tube gear generally has higher output impedances than SS."

True, that's why I said: "The cable was terminated with a 2.2K resistor at the far end (this reduced noise by over 10dB)."

"Modern servo-balanced equipment offers both low noise and high CMRR, mostly because of the use of modern op-amps especially designed for audio use."

What part of:

"An unbalanced line with a transformer at the amp end worst case can still be 50dB quieter than electronically balanced equipment under the same worst case conditions. Most gear on the market is electronically balanced, this adds noise and distortion from the extra circuitry, and can cause a loss of clarity compared to an unbalanced system that is properly terminated. Electronically balanced equipment is much poorer at RFI rejection than transformer balanced equipment. "

Didn't you understand?

And at the risk of repeating myself:

"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.

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. "

[Don Richard]

What part of:

"An unbalanced line with a transformer at the amp end worst case can still be 50dB quieter than electronically balanced equipment under the same worst case conditions. Most gear on the market is electronically balanced, this adds noise and distortion from the extra circuitry, and can cause a loss of clarity compared to an unbalanced system that is properly terminated. Electronically balanced equipment is much poorer at RFI rejection than transformer balanced equipment. "

Didn't you understand?

I wrote nothing about electronically balanced inputs. I wrote about servo-balanced inputs:

"Modern servo-balanced equipment offers both low noise and high CMRR, mostly because of the use of modern op-amps especially designed for audio use."

A servo-balanced input does not consist of :

the opamp + four 1% resistors

A servo-balanced circuit consists of (at least) two (2) op-amps with their feedback paths each cross coupled to the opposite op-amp.

If you find that any balanced input has to reject anything like 60dB of noise, you might ought to remove the source of the noise or use better shielding and grounding practices. In the case of a portable sound system that might not be possible, so one uses band-aids so the show can go on. With an installed system one has the time to do it right, and one should.

[Q-Man]

I have a lot going on in my system, and I used to have hum and buzzing coming from my speakers.

For all my long runs ( 35' and more) I switched to RG6 Quad shieled coaxial cable with RCA conectors. I did this about three years ago and now you can put your ear to all ten speakers plus subwoofer and not hear a thing. I even put some of the cables in conduit, but that may have been over kill?

[InVeNtOr]

^^^^^ thats a great way of doing long runs. great job about getting the quad coax. very cheap and easy. did you use wall plates, or run them out of the wall? the only thing i didn't like about doing that was the gauge of the coax. most are 18awg, and the larger gauges get very expencive very quick.

[Don Richard]

For all my long runs ( 35' and more) I switched to RG6 Quad shieled coaxial cable with RCA conectors

Be careful when using RG-6 for interconnects. A lot of this stuff uses copper plated steel center conductors, which would be OK for RF because of skin effect. Ensure that you are buying RG-6 with solid copper center conductors for audio interconnects, Parts Express sells both types.