Found this very interesting
08-02-2015, 06:37 AM
#2
The science is there and viewing the video will provide links to graduate level engineering discussions! 
The key is finding out what your amp is designed to take. Darned if I've ever seen a differential amp for a car but then I've not looked beyond the basics. If your amp is differential it makes sense to use twisted pair. I have a basement full of state of the art audio equipment. But the state of the art has moved well beyond my stuff! My car radios all lack external amps.
-- Chuck
The key is finding out what your amp is designed to take. Darned if I've ever seen a differential amp for a car but then I've not looked beyond the basics. If your amp is differential it makes sense to use twisted pair. I have a basement full of state of the art audio equipment. But the state of the art has moved well beyond my stuff! My car radios all lack external amps.
-- Chuck
08-24-2015, 02:35 PM
#4
Wow. That was a little scary. "You have a single-ended amp if there is less than 1000 ohms to ground". ??? I'd suspect a bad ground or a broken amp if I measured more than an ohm to ground.
And he completely forgot the part where twisted pairs eliminate most induced noise simply because they are twisted pairs, regardless of what input circuitry is in the amp. Remember telephones? (the kind with wires) Telephone transmission cables were always twisted pairs so that one conversation did not get induced onto another pair of wires, even after running parallel to it for miles in the same bundle. These days we use twisted pairs in CAT5 and CAT6 cables so that transmit and receive data streams don't interfere with each other.
What we're really talking about is the difference between "balanced" and "unbalanced" signals. Balanced means both signal wires have the same potential relative to ground. Unbalanced doesn't - typically one wire is ground. In an unbalanced system, electrical noise that is relative to ground will be reproduced, whereas with a balanced system it will not. That much of his explanation was correct. And that it does you no good to use balanced cables unless both your HU and the amp are designed as balanced.
You can find lots of equally almost-correct explanations on the Internet, such as this one - http://www.portlandmusiccompany.com/...unbalanced.php. I particularly like where he says the higher level of the unbalanced signal is supposed to magically add 6-10db of headroom to your amp. He probably has a "grounding kit" on his car, for the extra 20 HP.
clennney99 - That's not a "filter" he's talking about, it's a different amplifier design, and it has nothing to do with the amp handling a high-level signal. Most amps handle a high-level signal by simply reducing it back to "normal" levels before it gets to the amp input circuitry. I admit I'm not up on current car audio trends, but I'd be surprised if HU and amp designers are really moving to unbalanced signals. It wouldn't hurt, but gaining 10db in electrical noise reduction when you have 70db of background audio noise doesn't seem like that noticeable of an improvement to me.
And he completely forgot the part where twisted pairs eliminate most induced noise simply because they are twisted pairs, regardless of what input circuitry is in the amp. Remember telephones? (the kind with wires) Telephone transmission cables were always twisted pairs so that one conversation did not get induced onto another pair of wires, even after running parallel to it for miles in the same bundle. These days we use twisted pairs in CAT5 and CAT6 cables so that transmit and receive data streams don't interfere with each other.
What we're really talking about is the difference between "balanced" and "unbalanced" signals. Balanced means both signal wires have the same potential relative to ground. Unbalanced doesn't - typically one wire is ground. In an unbalanced system, electrical noise that is relative to ground will be reproduced, whereas with a balanced system it will not. That much of his explanation was correct. And that it does you no good to use balanced cables unless both your HU and the amp are designed as balanced.
You can find lots of equally almost-correct explanations on the Internet, such as this one - http://www.portlandmusiccompany.com/...unbalanced.php. I particularly like where he says the higher level of the unbalanced signal is supposed to magically add 6-10db of headroom to your amp. He probably has a "grounding kit" on his car, for the extra 20 HP.
clennney99 - That's not a "filter" he's talking about, it's a different amplifier design, and it has nothing to do with the amp handling a high-level signal. Most amps handle a high-level signal by simply reducing it back to "normal" levels before it gets to the amp input circuitry. I admit I'm not up on current car audio trends, but I'd be surprised if HU and amp designers are really moving to unbalanced signals. It wouldn't hurt, but gaining 10db in electrical noise reduction when you have 70db of background audio noise doesn't seem like that noticeable of an improvement to me.
08-24-2015, 03:55 PM
#5
I believe some of the newer OEM systems with separate amps do this, probably because it's easier
to run twisted pair than well-shielded single end cables. It wouldn't surprise me if aftermarket
amp makers have responded by adding circuitry to support either method, but I don't know.
to run twisted pair than well-shielded single end cables. It wouldn't surprise me if aftermarket
amp makers have responded by adding circuitry to support either method, but I don't know.
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