I received the Creek OBH-11 (standard, non-SE) headphone amp yesterday, and just did a few tests with nothing connected to it, and the headphone out going to the analog line inputs on my Audiophile 24/96 card.

Lowest volume on the pot (volume knob):

Left Right
Min Sample Value: -13.73 -13.61
Max Sample Value: 17.24 16.63
Peak Amplitude: -65.57 dB -65.88 dB
Possibly Clipped: 0 0
DC Offset: 0 0
Minimum RMS Power: -95.38 dB -94.9 dB
Maximum RMS Power: -67.02 dB -67.14 dB
Average RMS Power: -77.86 dB -77.92 dB
Total RMS Power: -76.31 dB -76.37 dB

Using RMS Window of 50 ms


Highest volume on the pot:

Left Right
Min Sample Value: -14.24 -13.68
Max Sample Value: 17.79 17.8
Peak Amplitude: -65.36 dB -65.35 dB
Possibly Clipped: 0 0
DC Offset: 0 0
Minimum RMS Power: -89.14 dB -88.66 dB
Maximum RMS Power: -67.5 dB -67.73 dB
Average RMS Power: -78.04 dB -78.04 dB
Total RMS Power: -76.87 dB -76.88 dB

Using RMS Window of 50 ms

Pretty good! There seems to be no significant noise added when increasing volume to maximum (or anywhere in between) with no source connected. I'm guessing that using a linear regulated wall wart [AC adapter] would diminish those low level amplitude fluctuations, unless it's from RFI -- perhaps a choke on the wall wart cable could help with that.

Adding a low-level source, the volume increases smoothly and gradually as it should.

P.S. the amp sounds pretty good, too.

A more realistic measurement would have some low impedance source (the AP outputs or a 200 ohm resistor) connected to the amp inputs. "Free" inputs may be noiser that the real thing.

What seems interesting is that Creek gives a S/N ratio of 65dB in their literature, which corresponds almost exactly to my measurement (if you figure -65dB peaks). It seems Creek was being conservative and/or accurate in reported measurements, which is refreshing in a "high end" audio company .