Mytek Digital Stereo 96 ADC (VER.7/sep 2010) - Manual (Page 9)

Analog Input Alignment
When using internal trimpots analog input level needs to be aligned
using an approx 1kHz sinewave fed from +4dB balanced source. The
alignment does not affect audio quality, only input sensitivity. The
alignment is performed using 10 turn trimpots inside the unit (see:
"Internal Jumpers"). A small tweaker or screwdriver is necessary.
You have to arbitrarily decide what will be your studio "0 VU"
analog/digital reference level. It is usually between -20 and -14dB. It
defines how much headroom you have left over the normal operating
"0 VU" level. You may set it at the same level as other piece of
equipment in your studio. For example Panasonic 3700 is fixed at -
18dB (which is low for most rock and roll recordings). ADAT is fixed
at -15dB which is a typical optimal level.
1.Set the oscillator in your console at 1kHz and "0 VU". Send the
oscillator to the ADC analog input."0 VU" at + 4dB corresponds to
1.225 Volts RMS measured between pin 2 and 3 of the output XLRs.
If you do not have an analog oscillator, you can use a calibrated
analog out of a DA converter and generate the sinewave inside the
DAW.
2. Connect a digital PEAK meter to a digital output. If you don't have
a dedicated digital meter use the most precise meter available in you
existing digital recording equipment or DAW.
3. Adjust the analog input level to get appropriate reading of the meter
(for example -15dB).
The alignment has to be performed with accuracy of 0.1dB to be
considered accurate.
Similar alignment procedure with 0.1dB accuracy is required for valid
A/B listening comparisons between different pieces of equipment. A
slightly louder source is typically perceived as "better" sounding.
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