# signal differences: rca vs speaker level



## mk1982 (Jul 3, 2005)

just wondering why RCAs are used over speaker outputs .. from an electrical point of view how do the two vary .. obviously the RCA offers noise shielding however besdies that i can't see what information RCAs can carry to the amp that speaker level inputs can't


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## Oliver (Jun 25, 2007)

One carries preout volts,[ signal only ] and one carries volts and amps, [ you can power the speakers with it.

I guess if the next device in the signal path doesn't have "high level ' inputs you'll need a LOC.

If you are just going from a HU to an amp,[ that has high level inputs ] you are all set.

In the search for optimal noise control, some go with "fiber optics", I have heard it said " light doesn't carry noise", I have read quite a few posts where the Ainet connections made for some noisy H700's.

If it ain't broke don't fix it, if the noise floor after amplification is low enough for you then use the speaker outputs.


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## durwood (Mar 7, 2007)

You are less likely to get any distortion out of the preamp voltage vs high level speaker inputs. How can you guarantee your speaker outputs are not distorting as you turn it up? 

Other problem, is the frequency response of the speaker or high level outputs compared to the low level preamp output-your low level preamp should have a better/more stable frequency response.


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## exmaxima1 (May 31, 2007)

durwood said:


> You are less likely to get any distortion out of the preamp voltage vs high level speaker inputs. How can you guarantee your speaker outputs are not distorting as you turn it up?


I tend to believe that speaker level outs can do better than RCAs for 2 reasons:

1. Most modern speaker level outs are balanced---neither conductor is at ground---and can potentially suppress noise (common mode rejection). RCA's are usually single-ended and rely solely on the quality of shields for the same function.

2. When used for signals, and driving a much easier load of perhaps 200 ohms and NOT a 4 ohm speaker, the distortion of speaker outs can be miniscule. And the low source impedance of the speaker outs can actually provide better frequency response while driving long cables. Think of it as a buffer on the RCA signal.

If the power amp has balanced differential inputs, then the results (especially the noise rejection) will be better with speaker level signals than when using single-ended RCA signals. 

I have heard great results both ways, but I firmly believe that speaker level signals have the best performance with the least potential for problems in an automotive application. BMW has been using this approach for years, as well as professional sound equipment and Zapco Symbilink.

Matthew


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