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Unbalanced Cables and Noise

TNTTNT

Standard Member
Hi, I could use some advice from the forum.

I have a choice which is: -

1. Run a line level stereo unbalanced 10m cable from an EQ device to a sub. The EQ device only has stereo balanced inputs and outputs. I need to convert to unbalanced signal with a converter jack, and feed to unbalanced stereo inputs on sub.


Pros - Using this method I can use the best EQ for my budget.

Cons - I am worried about noise over a 10m run.


2.Use a lower quality EQ device, but this one has the facility to sum stereo channels to mono. My sub has a mono balanced XLR input. I feed a mono XLR balanced line over 10m from EQ to sub.

Pros - No noise on 10m run

cons - much worse EQ device with much fewer useful facilities.

The crux of this for me is that will I get noticeable noise and hum on a 10m line level unbalanced cable?

I would rather not use the lower spec EQ device, but if the cable makes the sound worse, not sure if I have a choice.

There was a third option.

3. Buy a device which can sum balanced line stereo channels, and convert to a mono balanced output.

Pros - I could use the best EQ device, and have a 10m balanced line run.

Cons - The stereo to mono converter I have found (whether active or passive) cost between £150 to £250. This blows me over my budget.

Cons - I am not expert enough to make one, which I have been told is quite simple.

I hope you guys can help, because I wasn't sure if this is a Subwoofer thread, a Home install thread, or a cabling thread.

I thought since the crux of the matter is noise over a 10m unbalanced line level cable, this is the best place to ask.
 

TNTTNT

Standard Member
Guys,

Is this the right AV forum to ask? I thought it might be because essentially I am asking if it is ok to send an unbalaced line level stereo signal over a 10m cable.

Could you point me in the right direction.
 

dj-dulux

Active Member
I would try it, I would be supprised if you had a problem. Use the XLR output and send it down a balanced cable as normal. Do the bal to unbal, link 1 + 3 at the phono end, this is the generally accepted method (semi-balanced).

Just use good cable and try and keep it away from obvious sources of noise, use foil screened if possible, I use canford audio FST or FST-HD and have never yet had an issue with noise in 10m or so runs.

HTH,

Dupe...
 

TNTTNT

Standard Member
You're a gent. It sounds like you think I shouldn't have a problem. This means I can use a Behringer DEQ2496 to correct part of my room.

If noise on a 10m unbalanced run was a problem, I would have had to use a les well equiped device.

I might try somewhere like bluejeans to see if I can get a high quality 10m cable with XLR on one end and RCA on other.

Thanks again.
 

dingwall

Banned
It's impossible to say because nearly all the noise will come from the equipment itself, not the environment. Chances are, however, it won't be as audible as you may fear.

Foil shield cables are a bad choice - a braided shield with the lowest resistance should be used, it should be routed away from other cables, and kept to the absolute minimum length required.

You should never tie pins 1 and 3 together from balanced outputs without checking it is safe to do so from the manufacturer as this will damage equipment using active-balanced outputs.
 

TNTTNT

Standard Member
Could someone recommend an on-line supplier of 10m twin RCA to XLR (or balanced 1/4 TS) cables. Given the longer run, it would be great if the cable has a double braid copper shield. At least this is what I have been told.

I thought about making these cables. If I did go down this route, I would have three problems: -



1. I have never made one before

2. I don't know where I can get the cable I am after. Maplins is the most obvious choice, but I don't know how good their cut cable is, or connectors. Could someone reply with a link for a reliable seller and cable.

3. What do I bridge pins 1 and 3 on a balanced connector with. Do I use a small piece of shielded cable?

4. I can't find my soldering iron - but I can deal with that one.



Ideally I would rather pay and buy a high quality noise insensitive RCA to XLR cable. If you guys could recommend, I would be grateful.
 

TNTTNT

Standard Member
Sorry Dingwall, my post came at the same time as yours. At least we both agree that braided copper shield is the way forward.

I read the manual of the DEQ2496, and it says that if you put a unbalanced plug on the input or output, it will sense and automatically correct the level by 6db. I guess this means it is designed to take either feed. The only thing I am not clear on is do I still have to bridge pin 1 and pin 3. I assume yes, as it probably sense ground on pin 3 and adjusts the output/input level.

If I went down the route of buying the ready made cable or making the leads, could you recommend the appropiate parts. I have a quick look at Maplins, and the variety makes it very confusing to know which is appropiate. It doesn't help when they seem to label every product premium, or something similar.
 

dj-dulux

Active Member
It's impossible to say because nearly all the noise will come from the equipment itself, not the environment. Chances are, however, it won't be as audible as you may fear.

Not sure I agree with this, but I have no hard evidence to say otherwise, if you could direct us to some info on this that would be great. My understanding has always being that the noise is generated by the environment, RF and EMC from radio transmitters, power cables, equipment etc.

Foil shield cables are a bad choice - a braided shield with the lowest resistance should be used, it should be routed away from other cables, and kept to the absolute minimum length required.

If you look at the way I have suggested it is wired you will see that this is not the case. I am suggesting that the normal return wire (3) is used as an additional drain. Also FST is a pro product and the foil drain is the same cable mm2 as the conductors anyway. Foil is the standard install cable for just about every pro environment, its the only 100% screen, braid is only used if flexibility is needed and a compromise is made on the screening performance.

You should never tie pins 1 and 3 together from balanced outputs without checking it is safe to do so from the manufacturer as this will damage equipment using active-balanced outputs.

Unlikely these days, every manufacture ensures that hardware is 'joe public' proof, I have never come across anything where shorting pin 1 and 3 would cause damage, maybe some exotic valve stuff?

Any of the cable advertisers on here will make you something...

Dupe...
 

TNTTNT

Standard Member
If you look at the way I have suggested it is wired you will see that this is not the case. I am suggesting that the normal return wire (3) is used as an additional drain

Ah, thanks. It shows how dumb I am, because I didn't pick up properly on the 3 wire cable bit. What you are saying is use twin wire + shield cable. Connect one wire to pin 1, the other to pin 2 and shield to pin 3. On the other RCA end, the shield and pin 1 to shield connector. This way you don't have to bridge.

Also FST is a pro product and the foil drain is the same cable mm2 as the conductors anyway. Foil is the standard install cable for just about every pro environment, its the only 100% screen, braid is only used if flexibility is needed and a compromise is made on the screening performance.

I don't kmow enough about this. The only reason why I though copper braid shield was better was because I read that noise is partly due to resistance in the shield. If there was zero resistance, there would be no ground hum, and that aluminium has a higher resistance.

Would this work?

Canare L-2E5 Mini MIcrophone Cable at Markertek.com
 

dj-dulux

Active Member
Pin one in screen, two is Live, three is Return, XLR. Then at the phono end one and three get connected.

Canare cable is good stuff, but that stuff you have linked is a little thin.

Dupe...
 

dingwall

Banned
TNTTNT - if your equaliser manual says it "senses" an unbalanced connection, then the balanced output is a servo type. This means you must use a balanced plug (XLR or TRS) at the equaliser end. The plug at the subwoofer end is an unbalanced RCA phono obviously. It also means you must bridge the 'cold' output to the 'ground' output - i.e. bridge pins 1 and 3, or Ring to Sleeve. You can do this at the equaliser end, and run a one-conductor-plus-shield cable. Or you can do this at the subwoofer end, and run a two conductor-plus-shield cable. Either way, an easy route to do this is to use an adapter which does the bridging (these are less than a couple of quid) and then buy a pre-terminated cable.

Personally, I would try an XLR to RCA adapter (which bridges pins 1 and 3) at the equaliser, and run with a Mark Grant subwoofer cable. You may like to buy one run first before buying the second.
 
Last edited by a moderator:

TNTTNT

Standard Member
Guys,

I am sure that no intentional offense was meant by either party, and perhaps the shortest reply isn't always the best, if not economical.

Also, I have to pass thanks to both gentlemen, as I have been struggling to understand the implications of my cabling issues, so to find a place like this is like a small sanctuary of knowledge.

Hopefully to move things on, I re-read the manual and it says that pins 1 and 3 have to be bridged, for it to recognise the unbalanced connection, and make level corrections.

Out of interest, it seems another source thinks both ways are right. If you look at diagram 6, it suggests using 2 conductor cable, as DJ-Dulux suggested, and to also bridge, as Dingwall suggested.

Sound System Interconnection

Could I ask another thing? I have seen quad core mic cable. Would this be better than 2 core in terms of an unbalance signal, and avoidance of noise?
 

dj-dulux

Active Member
Guys,

Out of interest, it seems another source thinks both ways are right. If you look at diagram 6, it suggests using 2 conductor cable, as DJ-Dulux suggested, and to also bridge, as Dingwall suggested.

Sound System Interconnection

Could I ask another thing? I have seen quad core mic cable. Would this be better than 2 core in terms of an unbalance signal, and avoidance of noise?

Interestingly I use an old rane guide from 15 years ago or so, thanks for reminding me about the site, its a good resource. Either way is OK, I don't think thats what dingwall thinks I have wrong, but in general most people run the 2 core method (in pro land), its more flexible as if you did have an issue and the cable is in a fixed install you can change to balanced easily. Electrically both methods are the same and will work fine.

Starquad is probably OTT for what you are doing, I used to use it many years ago, but never really found it gave any practical advantage and was more difficult to terminate.

Dupe...
 

MarkTaylor

Well-known Member
Ad Hominem comment and related posts removed.

Please feel free to debate any of the questions raised in this thread at any time but please avoid directly attacking an individual making comments or asserting that facts stated are wrong without explaining what and why.

Mark Taylor
Moderator
 

ben.bayliss

Active Member
I'd second what dj-dulux says. Starquad is very posh but overkill for what you need. 10m isn't a very significant length cable wise so unless you've some really bad local noise problems you won't notice any difference vs. regular mic cable.
 

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