RCA Out To AES/EBU In To DAC

Your digital source is probably S/PDIF format. AES/EBU is the professional format. I don't know the details, but they are not the same. However the Behringer DEQ2496 manual says "The AES/EBU interface is largely compatible to the popular S/PDIF interface". "Largely"?? There may in fact be a problem such as you are seeing, because the Behringer makes provision to select either of these digital formats.

Wrong pinout. You need a RCA to AES/EBU digital cable.

I appreciate the previous posts. Specificallly, the DAC is the EMM Labs DAC 6, and the digital source is the Squeezebox 3. I could not find any discussion in the EMM Labs manual about this issue. The EMM Labs does have a BNC input connector, but as far as I could determine, this is used for feding an external clock signal to the DAC. Can anyone enlighten me further concerning the DAC 6?
Thanks,
Dennis

AES/EBU works at 110 ohms, S/PDIF works at 75 ohms. The impedance mismatch will still allow a signal to get through, but it is not optimized. There are format converters boxes that will properly do the conversion.

Get yourself a Monarchy Audio DIP (believe it stands for "Digital Interface Processor", there have been a few versions, they aren't very expensive new or used). This small, well-made box will take your S/PDIF and convert it to AES/EBU, while also providing electrical isolation between the source and DAC (just in case the spurious noise is caused by something else), as well as performing jitter-reduction. (Place the DIP away from other, line-level components to the extent that you can, particularly phono preamps.)