Hi,   it was measured with instrument (single ended) input.   The measurement from balanced output (TRS 1,2) to balanced line input (TRS) is here:   web.telecom.cz/macura/focusrite_line_balanced.pdf  

web.telecom.cz/macura/focusrite.pdf Please check my Rightmark measurement, it is very different from the one posted here in the beginning of the thread.

Quote: Originally Posted by Xakepa IMHO, 634 is flat and dull in a way, slightly shadowing detail and attenuating top high end. Every buffer will...to a degree, as they all have finite slew rate, so they're (neccesery) evil. This is probably wrong pressumption. The BUF634's slew...

I have added my recommended headphone amp schematics to the page. http://www.pha.inecnet.cz/macura/buffer_en.html

Anything new?