I just made some gain measurements of the MT's line stage. I also tried to measure how much gain is added by the push buttons.
My tests focused on the 1/4" inputs and the 'H' setting (Line in mode). I collected some M mode data but the file doesn't seem to be here.. My CF card may have filled up.
Summary
On the lowest gain setting, the MT adds a minimum of 14.81 dB of gain.
The clip light seems to come on at -1.0 dB.
In Line-in mode, each press of the level button adds about 0.5 dB.
The meters of the MT are divided by 10 bars. Generally, each bar represents 1dB. But each button press does Not move the same amount across the bar scale.
When the signal level hits the 10th bar, you're probably clipping.
In the table below, bar 1.0 is having the level setting arrow tip aligned with the first bar. It is not possible to align the tip on every bar (3.0).
Line in mode
Gain setting vs. dB
Bars dB
0 14.81
1.0 15.25
2.0 16.27
2.8 17.23
3.5 18.25
4.0 18.76
4.25 19.21
4.75 19.67
6.0 21.17
6.9 22.17
8.2 23.66
8.9 24.69
9.1 25.14
9.5 25.64
Now that we have a reference for how much gain the line stage adds, it will be much easier for others to test the Medium gain setting.
Test detail
I played a 440 hz sine.wav from my PC via USB to UA5's RCA jacks and into my 722 via an XLR adapter. I set the 722 gain at 0.0 dB and adjusted the UA5 output signal level until the -20dB on the 722 (while in "Peak" mode) lit.
Analyzing that file in Wavelab, the peak level was -19.83 dB.
I fed this signal into the 1/4" inputs of the MT while in line-in mode. I noted the gain setting and time offset of the recording. I then analyzed each gain level in wavelab.
A second test file was created where I set the UA5 signal strength so that the VU level on the MT would be at 5 bars when the MT gain was set to the minimum. That peak signal level from the UA5 was calibrated with the 722 and wavelab at -27.13 dB.
Weird bug
As I continued to increase the gain once the clip light came on, the level portion of the meter began to flash. Once further gain was added, the flashing stopped and the bar stayed unshaded, as if no signal was present.