Some measurements of my Grade A - "128dB"
Mono mode, 4.5V range
ASIO4ALL v2.15 Beta 2
ARTA 1.9.4.1 ("Mic" FR Compensation file to limit to 20Hz-20kHz)
Virtins Multi Instrument 3.9 (20Hz-20kHz)
On the left with MI, on the right with ARTA
Open loop
48kHz Sampling rate
FFT with Rectangle windowing, 32k FFT Window size
Above, A-weighted, below un-weighted
Noise is at
-127.7dBFS(A) (both tools give the same value)
or
-125.6/-125.7dBFS (<0.1dB difference between the 2 tools)
192kHz sampling rate
128k FFT Window size
All the rest, same as above
Above Un-Weighted, below A-Weighted
Noise is at
-127.9dBFS(A) (both tools give the same value)
or
-125.8/-125.9dBFS (<0.1dB difference between the 2 tools)
With a 150 Ohm load
(shared accross the 2 inputs), at 192kHz, for both tools
Noise is at
-127.7dBFS(A)
or
-125.6dBFS