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Unbalanced RCA louder than unbalanced RCA to TRS

post #1 of 3
1/11/11 at 4:45pm
Thread Starter 

I have the Essence STX in which the analog out is RCA. I also have the M-Audio CX5s. I had my CX5s hooked up via unbalanced RCA to TRS and when listening to music at a "normal" loudness, the dial on the Essence STX control panel was around 14-15. The CX5 also has an RCA input so you can use them as completely unbalanced. I recently(last night) acquired some nicer(build quality, connectors) RCA cables, and decided to use those to connect the CX5s to the STX. Now the volume has "doubled". Whereas I used to listen at 14-15, I now listen with the dial at 7-8. Is there any explanation as to why? I am completely at a loss as to why this might have happened. Any help would be appreciated. 

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post #2 of 3
1/11/11 at 5:12pm

Yes, this is expected.  An unbalanced RCA is a -10 Dbu signal.  That means that it follows a consumer audio standard where unity gain is -10 decibels from a certain reference level.  Balanced pro audio has a reference level of +4 Db.  So it's a little less (the reason for a little less is complicated) than 14 decibels louder.  Which means if you send a consumer RCA signal into an input that's expecting balanced TRS, the unbalanced RCA will be much quieter than it is expecting.

 

On top of this, balanced lines contain a positive, negative (or inverted), and ground.  Unbalanced lines only contain a positive and ground.  If the inverted signal is missing on a balanced input, you lose 6 decibels of volume, because only half the signal is there.

 

The short version is, that plugging an unbalanced RCA into a balanced input with a cable conversion can be up to 20 decibels quieter than an RCA input or a real balanced signal into a balanced input.

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post #3 of 3
1/11/11 at 5:34pm
Thread Starter 
Quote:
Originally Posted by barleyguy View Post

Yes, this is expected.  An unbalanced RCA is a -10 Dbu signal.  That means that it follows a consumer audio standard where unity gain is -10 decibels from a certain reference level.  Balanced pro audio has a reference level of +4 Db.  So it's a little less (the reason for a little less is complicated) than 14 decibels louder.  Which means if you send a consumer RCA signal into an input that's expecting balanced TRS, the unbalanced RCA will be much quieter than it is expecting.

 

On top of this, balanced lines contain a positive, negative (or inverted), and ground.  Unbalanced lines only contain a positive and ground.  If the inverted signal is missing on a balanced input, you lose 6 decibels of volume, because only half the signal is there.

 

The short version is, that plugging an unbalanced RCA into a balanced input with a cable conversion can be up to 20 decibels quieter than an RCA input or a real balanced signal into a balanced input.


Thank you very much. I learn something new everyday. At first I thought maybe I did something wrong, but I kept switching the cables, and it was the same time after time. Thanks for the reply, and easily understandable explanation. 

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