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how to convert unbalanced to balanced

post #1 of 16
Thread Starter 
Hi,
I have a long run (30ft) of balanced cables that use to use from my preamp to 3 power amps that are close to my speakers in a HT configuration. Now I would like to use a processor that only have RCA's outputs connectors. How can I use my courrent cables (balanced) with this unit and not having problems with noise because this long cable runs? do I need a unbalenced to balanced converter or just the adapters?. The main idea is to mantain the same quality and noise-free sound that Im having now. Thanks in advanced for your help.
post #2 of 16
Try adapters first (cheap solution). If that doesn't work, get the Jensen box.

- Steve O.
post #3 of 16
Thread Starter 
Thanks Steve. I found the jensen Iso-max PC-2XR box ( I think you refear to this) and -as per the manual- is balanced to unbalanced and what I need is the opposite (balanced to unbalanced). Sorry for my ignorance but is the same connect one way or the other?. Thanks again
post #4 of 16
Here is an in depth article about balanced wiring.
http://www.dplay.com/dv/balance/balance.html

Here is a quick and dirty solution.
http://www.faqs.org/faqs/theatre/sta...ection-27.html

Markertek would sell what you need for a reasonable price. Something like this should work.

I find that many times that the tips in the second article work quite well without buying anything. If you try them and get hum/noise you will probably need a transformer. I bet thats all thats in that little black 80 dollar box. Radioshack had something cheap back in the day, but I can't find it on their website... maybe I'm not looking in the right place though.

-Sean
post #5 of 16
Quote:
Originally Posted by jorsan View Post

Hi,
I have a long run (30ft) of balanced cables that use to use from my preamp to 3 power amps that are close to my speakers in a HT configuration.

I don't get it. Why not locate the power amps close to the preamps and connect them normally? Then you have a perfectly balanced connection for the distance to the speakers in the form of the speaker cable with no converters required. Much better noise immuity, less expensive and less complicated.
post #6 of 16
Thread Starter 
Thanks for the info. About the phisical location of my amps, I prefer to try other options first. I always have tried to run the shortest speaker's cables as possible.
I'll try all your ideas and after that I'll report.
post #7 of 16
Quote:
Originally Posted by jorsan View Post

I always have tried to run the shortest speaker's cables as possible.

No reason at all to do that provided they are of adaquate gauge. A speaker level connection has extremely high CMRR and noise immunity. Better than your line level connections will ever be.
post #8 of 16
Quote:
Originally Posted by NightHawk View Post

No reason at all to do that provided they are of adaquate gauge. A speaker level connection has extremely high CMRR and noise immunity. Better than your line level connections will ever be.

There is a fairly large camp that says short speaker cables are preferable to long speaker cables.

I use long speaker wires at present, but may rearrange and try the opposite approach just to see for myself if I can tell any obvious difference.
post #9 of 16
Quote:
Originally Posted by NightHawk View Post

No reason at all to do that provided they are of adaquate gauge. A speaker level connection has extremely high CMRR and noise immunity. Better than your line level connections will ever be.

I'm with you on this, line level has a far greater chance of interference than speaker level. I would be interested in hearing of negative results with longer speaker runs as compared to long balanced line level runs. As long as the loop resistance of the wire you use is 'within tolerance' you will be fine.

My only other solution would be some type of twisted pair conversion rather than unbalanced audio runs. You can do this rather cheaply these days, I like magenta reseach stuff. If you go to the www.magenta-research.com site, go to the products page and select audio, then the audio balun II product. Or, if you have deep pockets, invest in some type of CobraNet transmission system like the Biamp Audia stuff....
post #10 of 16
Quote:
Originally Posted by mjrtoo View Post

I'm with you on this, line level has a far greater chance of interference than speaker level. I would be interested in hearing of negative results with longer speaker runs as compared to long balanced line level runs. As long as the loop resistance of the wire you use is 'within tolerance' you will be fine.

Speakers represent a more reactive load than amp inputs. Some speakers have some wild impedance swings. Changing speaker cable length (and its associated impedance) can result in FR changes. Much less likely with competent interconnects.

As for noise, it is true that the line-level interconnects are more susceptible but, with good line drivers and appropriate cables, I've not had problems with >10meter runs in my main system.

Now, that's my bias but I do use short interconnects and long speaker runs in my other system. The reason is simple: I decide based on where I want to put my amps.
post #11 of 16
I have exactly that problem, and I solved it with an Ebtech LLS-8. I think it costs about $250 at places like sweetwater.com. There's also a 2-channel version that's cheaper (about $60). It's a very high quality piece of gear, and fully passive -- no noise added through opamps or other active electronics. And it doubles as a ground loop break, too!
post #12 of 16
Quote:
Originally Posted by whoaru99 View Post

There is a fairly large camp that says short speaker cables are preferable to long speaker cables.

I know and I don't think many people realize that the speaker level connection inadvertantly constitutes a perfectly balanced interconnect. Even on the cheapest equipment the driver end presents a very low impedance to ground to both wires and the speaker end presents identical high impedances to ground on both wires. These are the fundamental requirements for a balanced interconnect. There is little chance that undesired radiated fields will generate differential mode currents, the only currents to which the speaker will respond. This is the real reason why household 60 Hz fields are not a problem. There is also a parrallel two wire connection with little loop area and a high level desirable signal. Fat speaker wire can and should be inexpensive compared to balanced line level circutry and/or converters.
post #13 of 16
Quote:
Originally Posted by Kal Rubinson View Post

Speakers represent a more reactive load than amp inputs. Some speakers have some wild impedance swings. Changing speaker cable length (and its associated impedance) can result in FR changes.

I'm not sure about this. I would have to see the numbers. How much would the total reactance change with the cable reactance being so much less than the speaker reactance and how much would this impact FR. I don't know.
post #14 of 16
jorsan
Anyone that has attempted to use commonly available RCA-to-XLR adaptors to send an RCA line level output from a tape deck, CD or DVD player, into an XLR input of a pro-sound amplifier or mixer, knows the problem of levels being too low.

This occurs for two reasons:
•“Line-level” signal level for consumer audio equipment is nominally -10dBV (0.32V RMS). However, “line-level” signal level for pro-sound equipment is +4dBV (1.23V RMS). Simply put, pro audio gear is looking for a 14dB higher signal level.


•XLR inputs are “balanced”, in that the positive and negative components of the signal are carried on two separate conductors (hence the use of 3-pin XLR connectors). When using standard RCA to XLR adaptors, the line level signal is supplied only to the positive pin. The negative pin is either tied to ground or left open. This absence of half of the component creates a -6dB signal deficit.

Conversely, when coming from the record output of a mixing console, or similar equipment, to send to a consumer tape deck, computer sound card or VCR, the line level is often far to hot to be usable.
transformerless convertion is best
post #15 of 16
Quote:
Originally Posted by jorsan View Post

Hi,
I Now I would like to use a processor that only have RCA's outputs connectors..

I'd wait for the Outlaw 997 prepro. It will have balanced outputs.
post #16 of 16
Quote:
Originally Posted by michael keith View Post

jorsan
Anyone that has attempted to use commonly available RCA-to-XLR adaptors to send an RCA line level output from a tape deck, CD or DVD player, into an XLR input of a pro-sound amplifier or mixer, knows the problem of levels being too low.

This occurs for two reasons:
Line-level signal level for consumer audio equipment is nominally -10dBV (0.32V RMS). However, line-level signal level for pro-sound equipment is +4dBV (1.23V RMS). Simply put, pro audio gear is looking for a 14dB higher signal level.


XLR inputs are balanced, in that the positive and negative components of the signal are carried on two separate conductors (hence the use of 3-pin XLR connectors). When using standard RCA to XLR adaptors, the line level signal is supplied only to the positive pin. The negative pin is either tied to ground or left open. This absence of half of the component creates a -6dB signal deficit.

Conversely, when coming from the record output of a mixing console, or similar equipment, to send to a consumer tape deck, computer sound card or VCR, the line level is often far to hot to be usable.
transformerless convertion is best

Check out the input gain controls, and the output fader/pad controls. A pro mixer will NOT have the problems you are talking about, if you know how to run it correctly.
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