Originally Posted by George Mills
Even if ever does come.
I did not want to say it, but since you mention it, despite Mr. Stuart reassurance I am still a non-believer. Meridian has not even posted the V1.05 firmware for the HD621 on their site, although it seems already available for many months now. Seeing is believing ...

On topic: I do not believe you can test it with the equipment you have. M states it will remove pre-ringing caused by the 20kHz brickwall filter from the original recording, and your hi-def sources won't have that problem.