Thanks a lot for the answers.
You can do this with pretty much any stereo amp. The process is to invert the signal going into one half of each of your two amps. Then you configure the output +/- from the signal + output of each channel, the noninverted + output will remain as signal hot (+), the inverted + output will become signal cold (-).
Thank you, Doc. Yes, I knew that. It's not really necessary in my case because I want to use a balanced source. This is the reason why I thought in build a full symetric balanced amplifier: maintaining the signal fully balanced from the beginning until the end.
Or you could sell the Crack and use the proceeds to finance a Mainline, which is already set up to do this more cleanly and more easily. You could also do this with a S.E.X. amp by installing the impedance switching kit and making an adapter that goes from the speaker binding posts to whatever connector you use for your balanced headphone cable.
Doc, don't believe that I didn't thought it!
But, for the same reason, I don't want a SE amplifier and convert to balanced in the output as I think do the Mainline (I don't know deeply the Mainline and I can be wrong). I don't think that it will be a real improvement. In fact, the Mainline's reviews that I've read agree with the opinion that there are only a light improvement using the balanced output with the HD600. In this case, I prefer use the SE Crack that is really marvelous as well.
By doubling the amp and inverting the phase on one side, you create two other effects besides "balanced" outputs. These effects do not occur when you use a transformer to generate the balanced signal, as in the Mainline:
1) You have made a push-pull amplifier, which has quite a different distortion spectrum and does not sound the like a SE amp.
2) You double the output impedance, which is already a limitation of the Crack.
Thank you, Paul. That explains me the things.
