Good suggestion by Dave about the Jensen transformers. A number of Audiogon members have reported using them, with no perceivable sonic side-effects.
There is an excellent paper at Jensen's site about interfacing balanced and unbalanced equipment:
http://www.jensen-transformers.com/an/an003.pdf
Note that among the various approaches it describes, the adapter cable approach is shown for rca to xlr input, but NOT for xlr output to rca input. Although it certainly can be done sometimes, if the output impedance and drive capability of the output circuit permits, or if pin 3 is left open.
Here is a lower priced alternative to the Jensen transformers:
http://www.bhphotovideo.com/c/product/381596-REG/ART_DTI_DTI_Transformer_Isolator.html
http://www.artproaudio.com/downloads/specsheet/dti.pdf
I've used this device in non-critical voice recording applications, and in that application it has seemed perfectly transparent sonically.
I'm inclined to think that the problem is not due to noise floor sensitivity, because it seems to be inversely related to volume control setting, it is intermittent, and it is not present on the rca output (where the output level is only 6db lower than on the xlr output).
Good luck!
-- Al
There is an excellent paper at Jensen's site about interfacing balanced and unbalanced equipment:
http://www.jensen-transformers.com/an/an003.pdf
Note that among the various approaches it describes, the adapter cable approach is shown for rca to xlr input, but NOT for xlr output to rca input. Although it certainly can be done sometimes, if the output impedance and drive capability of the output circuit permits, or if pin 3 is left open.
Here is a lower priced alternative to the Jensen transformers:
http://www.bhphotovideo.com/c/product/381596-REG/ART_DTI_DTI_Transformer_Isolator.html
http://www.artproaudio.com/downloads/specsheet/dti.pdf
I've used this device in non-critical voice recording applications, and in that application it has seemed perfectly transparent sonically.
I'm inclined to think that the problem is not due to noise floor sensitivity, because it seems to be inversely related to volume control setting, it is intermittent, and it is not present on the rca output (where the output level is only 6db lower than on the xlr output).
Good luck!
-- Al