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post #1 of 5 Old Yesterday, 07:05 PM - Thread Starter
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Question Long distance RCA interconnects between amplifiers?

Hey all, bit of an odd question but first a dash of background: I upgraded my marantz SR8002 to a denon AVR-X4000 (right before they added atmos support, grrrr!). Now I'm planning on using the marantz to power the height speakers, and possibly double up the front channels (it'll power up to 7 channels, so I can in theory add 7 more speakers and since I have a collection of classic speakers and a quasi wall of sound is a fun concept... )

I want to place my old receiver on the far side of my theater room as there's a couple spare 20 amp dedicated circuits over there. This would mean running the RCA Pre-outs some 40 feet into the RCA 7.1 channel in of the secondary receiver. My thought is to get 50ft of XLR per channel and cap each end with an XLR to RCA changer. Anyways, the question is: am I being daft? Will this not function as I want it to? Am I incorrect that 50ft RCA cables while inexpensive, are.... cheap and would adversely effect the sound the second receiver is putting out?


Thanks!
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post #2 of 5 Old Yesterday, 08:08 PM
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You'll gain nothing and lose some $$'s in the process. You can't make a balanced cable from an unbalanced (single ended) cable. Your best bet is to get a good extension cord to power the Marantz and locate it closer to the rest of your gear.

If that can't be done get some quality RCA's from Mono-Price or Amazon in the length you need. Don't get extra - measure so you end up with the shortest possible length. I use a length of speaker wire - lay it out - mark it then measure it and get the closest length needed. I've used very thin RCA cable at 30' with some interference but it wasn't as bad as I thought it would be. I also have a 40' premium RCA cable from Mono-Price - works better than the thin one I was using. The premium RCA cables from Mono-Price is very good. The only thing I've found is their connector seems to fit rather tightly to the AVR and amp jacks. Turning slightly when removing helps.

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post #3 of 5 Old Yesterday, 09:20 PM
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Sorry, I have to disagree with this post ^^^ on at least the concept of using single ended to differential converter.

They work fine (I have used them myself for microphones plugged into 1/4" phone jack on guitar amps or 'PA' amps that were merely stereo receivers). The noise immunity and performance of the cabling and transformers will be similar to native balanced signal path implemented with active components. I also believe (but cannot prove) that some older (pre-IC) equipment used similar transformers internally anyway rather than bother implementing tightly balanced differential gain stages to obtain common mode rejection. Maybe someone with more relevant background can chime in here.

At the lengths you are considering, balanced connections might not make any audible improvement over plain RCA coax though. Depends on many factors, including that height speakers are synthesized from the program so their content is going to have artifacts anyway, particularly PLIIz seems susceptible according to reports on this forum (although Atmos has discrete height channels).

The noise is going to depend on the length and routing and how much EMI exists in your listening environment. The treble attenuation corner frequency is going to depend on the total capacitance of the wire (product of the characteristic c/l of the wire times total l) and the high frequency output impedance of the pre out. In both cases, keeping single ended wires short can only help things.

Regarding the 'tight' RCA plugs, this is a marketing ploy to make it seem that the connectors are higher in quality than they really are. It stems from the perception that cheap connectors with loose fitting oxide-prone metal often lose the connection from corrosion or complete lack of contact (or just fall out of the socket completely). Personally, I avoid overly tight RCA plugs because no matter how carefully inserted, they will excessively wear (if not break) the jack. Actual high quality connectors should fit snugly with a highly compliant springy ground connection (typically wrap-around instead of toothed) rather than risk damage to the sockets from excessively tight connection.

The other suggestion to place the height channel receiver/amp in the same location as the source and power it from an extension cord off a different circuit, will solve the signal issues but depending on the receiver and power you might still get ground loop issues. Probably not, but stranger things have happened. It is probably a better way to address the issue if you have room because speaker wire and extension cord is relatively cheap and a known performer.

If that receiver is only powering height channels it might not use much power anyway. If you have not done so, you should double check the power requirement and even test out the system with temporary install to see if you actually have a power issue or not. At those distances, the best solution is to use short cabling on everything except the speakers and plug every component into the same power source so they all share the same ground domain at the power strip and they all get the benefit of your power conditioner.
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post #4 of 5 Old Yesterday, 09:37 PM
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Neither of his receivers have XLR connections or I'd have recommended using them. Using an XLR cable is an unnecessary expense unless one already owns them. My reference to tight fitting RCA ends wasn't high praise - quite the opposite in fact.

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post #5 of 5 Old Today, 04:10 PM - Thread Starter
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Cool thanks guys, I wasn't thinking of gaining anything from the balance characteristics of the XLR, but rather from the thicker wire and better shielding in theory giving me a purer version of the signal than a 50ft RCA cable. I hadn't really considered permanent installation of a 50ft extension cord as it had always been hammered into me that this is a very bad thing (VBT tm) for computers/home theater. However as I have a bunch of extensions, and an extra spool of 12awg speaker wire, I can definitely try this for power usage and testing purposes (well, or I could just rotate my setup 180 degrees if I can figure out a good way to block light from the glass door that currently sits behind the projector screen... that would give each receiver it's own (almost, as I have to power the projector) dedicated circuit... Ponders.

For now I'll opt for the extension cord and speaker wire as that's no expense and you both agree on it


Thanks a ton!
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