RCA vs AES/EBU

[pmchoong]

I have my buffalo III up and running. The thing is that the RCA output has much more gain than the AES/EBU. Why is this so? If I play using the AES/EBU cable, I need to turn the volume up a few notch (eg. RCA's volume at 9 o'clock while AES/EBU at 12). Also, the RCA sounds sharper and more focus. Both RCA and AES/EBU cable are of the same type, except that the AES/EBU has an extra for the negative. With the RCA, the vocal seems to be at the front while the AES/EBU's vocal seems to be further behind. The instruments are also space further apart. Is this how it sounds?

[b1o2r3i4s5]

First we need to know what type of signal is coming out of the RCA output and where are you sending them to, since AES/EBU is a digital audio streaming protocol like S/PDIF and RCA is the name of a connector. As far as i know both analogue audio signals and S/PDIF signals use the RCA connector.

[merlin el mago]

RCA cable & connectors must have 75 ohms characteristic impedance and AES/EBU cable & connectors must have 110 ohms characteristic impedance. N.B. connectors both chassis & connectors both cable ends.

[pmchoong]

the signal is from the S/PDIF using RCA conectors. It is from the CD digital output. The AES/EBU is also from the CD output. These are connected to my buffalo III via the Sidecar. The side car is with 4 input, 2 x AES/EBU and 1xS/PDIF and the last is TTL. For the sidecar, I used the 110 ohm resistors for the AES/EBU input and 75 ohm for the S/PDIF input. The TTL is 10 ohm resistor.
I do not know the ohm of my cable.
Thanks.

[merlin el mago]

For 75 ohms it's easy: buy a coaxial antenna TV cable.

[merlin el mago]

"The instruments are also space further apart". Yes is how it sounds balanced.

[BrianDonegan]

The has nothing to do with the cabling, nor AES vs SPDIF, per se. The analog signal levels feeding the two outputs on your soirce are at a different level.

The voltage and impedance of the digital signal does not effect the analog signal level contained in the digital data it contains. For that you would need to alter the bits.

[pmchoong]

Originally Posted by BrianDonegan

The has nothing to do with the cabling, nor AES vs SPDIF, per se. The analog signal levels feeding the two outputs on your soirce are at a different level.

The voltage and impedance of the digital signal does not effect the analog signal level contained in the digital data it contains. For that you would need to alter the bits.

Which means there's nothing much i can do except to alter the bits of my cd player? This also means that the sound which i described in post #1 is exactly the sound which the manufacturer (of the cd player) wants it to be. Correct? I read in the BIII manual, a 47 ohm resistor is also included for the AES/EBU. Would this make a different?

Thanks.

[BrianDonegan]

The resistors are for setting the correct termination impedance. I doubt the CD player manufacturer thought people would be switching between the two outputs, so slight differences in absolute level was probably not a large concern.