Passive attenuator impedance question

Wow thats a lot of responses! Thank you!

Just to clarify, I do not wish to use a variable (stepped) attenuator. Currently I am using between 20dB to 35dB of digital attenuation in the DAC. All I want is to introduce fixed passive attenuation of 20dB. This will allow me to use 0dB to 15dB digital attenuation. Theoretically this should reduce potential digital degradation (if is any), but the attenuator could introduce its own.

To be honest, I don't detect loss of SQ in my system even when the DAC attenuates 35dB. Maybe my system or ears are not resolving enough :-). Having said that I just wanted to experiment with a fixed attenuator (built right into an XLR male connector to minimize signal degradation). Should be a fairly inexpensive experiment even with high quality resistors.

@Almarg
I am a little confused as to which circuit to use with balanced cables. Some websites suggest soldering the R2 resistor (1K in my case) between the + and - terminals and a R1/2 resistors (9/2 = 4.5K in my case) in series with the + and - wires. Other online sources suggest that using two R1 -- R2 voltage divider networks. One between + and ground and another between - and ground. Not sure which one to go with. Thoughts?

Gmudunuri, I suspect that either of those approaches would work well, but I'd suggest going with the three resistor approach. Not only because it would use one fewer resistor per channel, but because of some probably very minor but perhaps significant theoretical advantages.

One being that the four resistor approach may cause or contribute to signal current flowing in the ground connection between the two components (i.e., in the shield of the balanced cable), which may to some extent counteract the potential advantages of a balanced interface. Another being that with the four resistor approach if the exact values of the two 1K resistors are not well matched the result might be a slight degradation of common mode noise rejection. In the three resistor configuration the exact value of the 1K resistor is non-critical. You would still want to purchase 4.5K's having relatively tight tolerances, though, perhaps 1%.

There are also differences of a factor of 2 in impedance between the two configurations, both looking forward from the DAC (favoring the four resistor configuration), and looking back from the amp (favoring the three resistor configuration). But I don't think either difference would be significant with your particular components.

Good luck. Regards,
-- Al

I just received IRC 0.1% 1/4 Watt resistors. Went with double the resistence: 2K and 9K. Will try to put together the attenuator over the weekend and report my findings.