After a lot of opinions, and more than 6 mails exchanged with Audio-GD's Mr. Kingwa, I was about to order an NFB-6 for use with my HD650 and RS1i cans.
While my source isn't balanced (DAC19DSP) Mr. Kingwa informed me that the NFB-6 could output true balanced as it can convert the signal. All I need do was re-cable my headphones.
However, he informed me that the DAC19 being single ended, would only output 1.2MA, as opposed to 1.2MA x 2 for a balanced DAC and for the HD650, I might find volume level to be low.
Would this be the case? Can anyone who has used the NFB-6 balanced with an HD650 but through an unbalanced source comment?
The solution would be to solder a couple of resistors inside the DAC19, boosting volume level to 2.4MA and maintaining the same volume as a balanced DAC. Since I have zero knowledge of soldering, I don't know what to do.
1) Buy the NFB-6, try the volume level and see if its OK. Can anyone comment on the technical data mentioned above? Its mostly Greek to me!
2) Opt for the SA31SE instead and forget about balanced drive altogether
I do not want to remove my Ref 5 DAC off my loudspeaker setup, and I cannot afford to buy another balanced DAC this year.