Sorry to bump this thread, but I am really at a loss here. After intense googling and reading through many forum posts here, I still have not found a good answer to this problem. And unfortunately, the M-Audio forum has not been very helpful.
So my goal is to connect a headphone amp to my M-Audio Profire 610, as I have realised that the built in headphone amp is not very good. They do a decent job of driving my ATH-M50, but the beyerdynamic DT770 Pro / 80 sounds quite under-powered. And as mentioned previously, sometime in the not so distant future I plan to get the Ultrasone Pro900. I can see 4 different options, but I am really unsure what is the best way to go, considering the Profire only has balanced TRS line outputs and most amps in my price range seems to have only unbalanced RCA inputs.
1. Use the line outs from the Profire. This seems to me to be the best option, but I don't know anything about connecting balanced/unbalanced signals. Can I just get unbalanced TRS -> RCA cables, or will I need some special cables? And will I also need some converter box? Are there any other issues I should be aware of with this set up?
2. Use the headphone out from the Profire, and just get a 1/4'' -> RCA Cable. With this option, I am afraid the sound quality will suffer, as the signal into the headphone amp will already be somewhat amplified.
3. Use the S/PDIF Coax output from the Profire. The issue with this option is that I would then need to find an amplifier with S/PDIF coax in, which will limit my choice in amplifier. I am also a bit weary of introducing another digital step in to the signal chain
4. Find an amplifier with balanced inputs. This seems to be the most straight forward approach, but the cheapest one I have been able to find is the Lake People G103-P (269 Euro from Thomann). This seems to be a decent amp, but I am just a bit afraid of overspending. I don't want to find out later that a FiiO E09k for 99 euro could have given me the same/similar sound quality. Or alternatively, spent roughly the same amount of money for the Matrix M-Stage and gotten a much better sound.
My maximum budget is around EUR 300 (around USD 400), that would have to include amp, shipping, and any extra cables/converters I might need.
Any input to point me in the right direction would be much appreciated!
Thanks and regards