Long run and not enough gain to power rear channels... is it the interconnects? - AVS Forum
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post #1 of 24 Old 05-28-2012, 04:33 PM - Thread Starter
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I have a 40 foot run from my surround processor to the rear channel amplifier. I cannot get enough gain out of the surround processor to come anywhere close to reaching reference level. Could I be losing that much gain with the 40 foot interconnect run? I would love to go balanced but my equipment doesn't support it. Is there a cable that would work better? It was wired using Canare L-4E6AT just in case I could eventually do balanced.
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post #2 of 24 Old 05-28-2012, 04:51 PM
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Quote:
Originally Posted by scooter_29 View Post

I have a 40 foot run from my surround processor to the rear channel amplifier. I cannot get enough gain out of the surround processor to come anywhere close to reaching reference level. Could I be losing that much gain with the 40 foot interconnect run? I would love to go balanced but my equipment doesn't support it. Is there a cable that would work better? It was wired using Canare L-4E6AT just in case I could eventually do balanced.

No standard line audio cable, that is 22, 24, 26awg will lose any significant voltage at 40 feet. Must be something else.

If the rear amp has enough gain hooked directly to the processor then I would suspect the cable construction. If the Canare wire you used is the StarQuad stuff, make sure you have the same wire soldered on both ends. The StarQuad has two white and two blue wires that normally get tied together so it doesn't matter which one is which. But if you only use a single blue and/or white wire, make sure it's the same on both ends.

FWEIW, 40 feet is well within the limits of 16wag speaker wire for surrounds. You could probably get away with 18awg since surrounds aren't full range. Why not keep the amp next to the processor and run long speaker wires. Less chance of hum and noise this way too.

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post #3 of 24 Old 05-28-2012, 08:12 PM - Thread Starter
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It is the StarQuad with the foil shield as opposed to the braided shield. It is soldered together correctly.

So here is a question though... I am using one of the pairs for ground. The cable has a ground wire but seemed to make sense to use one of the pairs for ground. Was this a mistake?

I cannot move the amp unless I rip open the wall which is something I don't have an appetite for at the moment.
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post #4 of 24 Old 05-28-2012, 08:28 PM
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What speakers are they? Wondering if it could be due to sensitivity.
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post #5 of 24 Old 05-28-2012, 09:10 PM - Thread Starter
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Originally Posted by Brad Horstkotte View Post

What speakers are they? Wondering if it could be due to sensitivity.

This issue has nothing to do with the speakers. It is related in some fashion to the interconnects.
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post #6 of 24 Old 05-29-2012, 01:57 AM
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Quote:
Originally Posted by scooter_29 View Post

So here is a question though... I am using one of the pairs for ground. The cable has a ground wire but seemed to make sense to use one of the pairs for ground. Was this a mistake?

Yes, it was. The shield should be connected. If you want to use one of the pairs as signal ground that's fine, but the shield should be tied to it. Either way, that's a potential noise issue, though - not a signal-level issue.


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Originally Posted by scooter_29 View Post

This issue has nothing to do with the speakers. It is related in some fashion to the interconnects.

As Glimmie noted, that's highly doubtful. Perhaps you just need to re-balance the levels - like, reduce the volume of the other channels. That would force more signal to the rear channel amp.

Regards,
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post #7 of 24 Old 05-29-2012, 04:37 AM
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Quote:
Originally Posted by scooter_29 View Post

This issue has nothing to do with the speakers. It is related in some fashion to the interconnects.

How do you know that is true for sure?

What does an ohm meter say when you check the cables for continuity and absence of shorting?

If you are fabricating cables and you don't have either an ohm meter or a cable tester, you are walking on thin ice. People who do this a lot have both.

The current low price I see on eBay for a useful ohm meter is $4.09 Buy It Now (no auction), shipping paid. Your local Harbor Freight has them for similar low prices. Your local big box home improvement store wants several times that, but it should still be within your budget. We're talking the price of one connector or less!

Cable testers are somewhat more pricey, but are more convenient.
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post #8 of 24 Old 05-29-2012, 05:33 AM - Thread Starter
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Originally Posted by arnyk View Post

How do you know that is true for sure?
What does an ohm meter say when you check the cables for continuity and absence of shorting?

And what makes you think I didn't use one? They ring out just fine... no cold solders... no shorts.
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post #9 of 24 Old 05-29-2012, 05:38 AM - Thread Starter
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Quote:
Originally Posted by Wayne A. Pflughaupt View Post


Yes, it was. The shield should be connected. If you want to use one of the pairs as signal ground that's fine, but the shield should be tied to it. Either way, that's a potential noise issue, though - not a signal-level issue.


As Glimmie noted, that's highly doubtful. Perhaps you just need to re-balance the levels - like, reduce the volume of the other channels. That would force more signal to the rear channel amp.

Regards,
Wayne A. Pflughaupt



That is my problem as I unfortunately cannot get enough signal to the rear amp. I can turn the output to 100% on both the overall volume and the gain of the rears and am still not reaching reference but should be able to. I am going to try moving some gear around and see if a short interconnect makes a difference.
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post #10 of 24 Old 05-29-2012, 05:43 AM
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Quote:
Originally Posted by scooter_29 View Post

That is my problem as I unfortunately cannot get enough signal to the rear amp. I can turn the output to 100% on both the overall volume and the gain of the rears and am still not reaching reference but should be able to. I am going to try moving some gear around and see if a short interconnect makes a difference.

What amp do you use? Did you ever tried to connect it to your processor with other interconnects? And WHAT do you mean when say "reference level"?
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post #11 of 24 Old 05-29-2012, 02:19 PM - Thread Starter
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Originally Posted by ap1 View Post

What amp do you use? Did you ever tried to connect it to your processor with other interconnects? And WHAT do you mean when say "reference level"?

Reference Level
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post #12 of 24 Old 05-29-2012, 02:58 PM
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As others have said, not likely your interconnects. If you are concerned about this look for THX certified interconnects

What signal are you running to the rear when you do the tests? If it is rear channel from typical program material you will not get "reference" level since rear channels usually don't contain much content. If you are using full strength test signals, with amp and speakers capable of "reference" levels, then you should be able to get them. If you are using "pro" gear for your rear amp then you might be running into a mismatch between the output of "consumer" gear and the input the "pro" gear expects.

Everything I say here is my opinion. It is not my employers opinion, it is not my wife's opinion, it is not my neighbors opinion, it is My Opinion.
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post #13 of 24 Old 05-29-2012, 08:14 PM - Thread Starter
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Any engineers able to chime in as to what might be going on?

For those that keep throwing out the obvious, I am not new to this hobby and have been at it for >20 years...
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post #14 of 24 Old 05-29-2012, 09:57 PM
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Quote:
Originally Posted by scooter_29 View Post

Any engineers able to chime in as to what might be going on?

For those that keep throwing out the obvious, I am not new to this hobby and have been at it for >20 years...

I am An EE and have been building television broadcast and production facilities for over 25 years.

Ohm the cables out end to end. Use a long piece of 18ga bell wire for the meter return if already installed.

From center pin to center pin should be less than 10 ohms.

From connector shell (ground) to connector shell should be less than 10 ohms too.

From shield to center pin at either end with both ends unplugged you should at least a meg ohm.

If you read these values, it's not the cables.


P.S. use the shield instead of one of the wires for the ground as instructed above. Otherwise you could have hum problems.

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post #15 of 24 Old 05-30-2012, 04:56 AM
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Quote:
Originally Posted by scooter_29 View Post

Any engineers able to chime in as to what might be going on?

For those that keep throwing out the obvious, I am not new to this hobby and have been at it for >20 years...

...begging the question: "If you know so much about audio, why did you have to ask the question in the OP?" I have no problems with that question, but I do have a little bit of a problem with the apparent arguing and attitude expressed towards people who are trying to help.
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post #16 of 24 Old 05-30-2012, 05:26 AM
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Quote:
Originally Posted by scooter_29 View Post

Any engineers able to chime in as to what might be going on?

For those that keep throwing out the obvious, I am not new to this hobby and have been at it for >20 years...

Clearly 20 years is not enough for you to have become an expert. If you were expert you would not have this problem, and you would not have to ask this question.

You might want to give the engineers something to work with. So far all we know is the type of wire used . . .

Good luck solving your issue

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post #17 of 24 Old 05-30-2012, 06:10 AM
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I have to ask... For testing purposes, have you tried moving the preamp closer and using a shorter pair of interconnects, to see if the same problem with gain exist? That alone would tell you whether or not the issue is with the longer run.

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post #18 of 24 Old 05-30-2012, 06:11 AM
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The interconnects have nothing to do with the gain, but you will have much better system performance and lower noise if you run balanced connections. Unbalanced interconnects should be kept under 6 feet when ever possible.




Quote:
Originally Posted by scooter_29 View Post

I have a 40 foot run from my surround processor to the rear channel amplifier. I cannot get enough gain out of the surround processor to come anywhere close to reaching reference level. Could I be losing that much gain with the 40 foot interconnect run? I would love to go balanced but my equipment doesn't support it. Is there a cable that would work better? It was wired using Canare L-4E6AT just in case I could eventually do balanced.

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post #19 of 24 Old 05-30-2012, 06:13 AM - Thread Starter
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Quote:
Originally Posted by Glimmie View Post

I am An EE and have been building television broadcast and production facilities for over 25 years.

Ohm the cables out end to end. Use a long piece of 18ga bell wire for the meter return if already installed.

From center pin to center pin should be less than 10 ohms.

From connector shell (ground) to connector shell should be less than 10 ohms too.

From shield to center pin at either end with both ends unplugged you should at least a meg ohm.

If you read these values, it's not the cables.


P.S. use the shield instead of one of the wires for the ground as instructed above. Otherwise you could have hum problems.

Thanks Glimmie... this was the kind of advice I was hoping for.
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post #20 of 24 Old 05-30-2012, 06:21 AM - Thread Starter
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Quote:
Originally Posted by Rutgar View Post

I have to ask... For testing purposes, have you tried moving the preamp closer and using a shorter pair of interconnects, to see if the same problem with gain exist? That alone would tell you whether or not the issue is with the longer run.

Just verified again last night. The short run with a different kind of wire works fine.
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post #21 of 24 Old 05-30-2012, 07:00 AM
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Quote:
Originally Posted by scooter_29 View Post

Just verified again last night. The short run with a different kind of wire works fine.

You might look into something like this:

http://www.amazon.com/TC-780LC-Stere.../dp/B000RZXAHI

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post #22 of 24 Old 05-30-2012, 08:38 AM
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Quote:
Originally Posted by scooter_29 View Post

Thanks Glimmie... this was the kind of advice I was hoping for.

When you said you tested the cables, I presumed that you already knew about doing tests like the ones that Glimmie (properly) suggested.
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post #23 of 24 Old 05-30-2012, 08:41 AM
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Quote:
Originally Posted by Rutgar View Post

You might look into something like this:

http://www.amazon.com/TC-780LC-Stere.../dp/B000RZXAHI

If using different cables fixed the problem (please see his post just above yours), then the above is completely unnecessary.

I presume he was posting at the same time you were and you couldn't see his latest reply.
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post #24 of 24 Old 05-30-2012, 11:59 AM
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Quote:
Originally Posted by commsysman View Post

The interconnects have nothing to do with the gain, but you will have much better system performance and lower noise if you run balanced connections. Unbalanced interconnects should be kept under 6 feet when ever possible.

Balanced is indeed the best way for long audio runs but keep in mind that full balanced I/O can be very expensive for a consumer to implement if the devices don't already have balanced I/O ports.

Good transformers are at least $100 per channel and you will need two per channel, one for each cable end. Active converters such as the Radio Design Labs products cost about $200 per stereo cable end. So that's $400 for a basic stereo run.

So by all means try it first unbalanced and see if the hum is objectional. Running a shielded pair cable is very smart should you need to upgrade to balanced in the future. For unbalanced just ignore the additional wire or tie it with the shield. Quad Star is mainly for microphones where you have very low signals. It's a bit overkill for line level audio but fine if you don't mind the cost.

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