1 (edited by KSTR 2019-02-27 15:31:09)

Topic: Adi-2 Pro Feature Request: Analog Level Meter Screen

When using the Adi-2 Pro especially in a measurement setup, it is currently is *not* straightforward to read the true analog peak level range and currently measured value in absolute voltage units. Instead, one must manually calcualate the voltages from the current gain applied to the output or input we look at, using the corresponding setting of the Reference Level.

For example, to output a +10dBVrms (3.16Vrms, 4.5Vpk) sine on XLR1/2 one has to determine which Ref.Level must be used and which corrective gain must be applied digitally (either by the RME or by the source) to a 0dBFS input signal.
+10dBV is +12.22dBu, so the +13dB range is sufficient and the level must be decreased by 0.78dB.

Getting 20Vpk from the phones output, this means 14.1Vrms which is +25.2dBu, hence we need to select balanced phones high power mode as that is the only output of delivering more than +24dBu, and reduce level by 1.2dB.

For the analog inputs it is pretty much the same just backwards, for example if we have a reading of -4dBr and the Ref.Level is +19dBu and a trim gain of +3dB is present then what's the actual voltage present at the input?
+19dBu - 3dB - 4dB is +12dBu, which is 9.78dBV/4.36Vp

Obviously, this isn't very convenient.
Note that the scaling that must be applied to get the max range and current value, is one out of eight(!) different scale factors for the analog outputs, and the analog input has even more values coming  from the Ref.Level and 0.5dB steps of 6dB max trim gain.

If I got the numbers right, the following table gives the 0dBFS equivalent voltages for the various analog ports and setting. Peak Volts would be a natural choice of unit, as plain value [Vpk] / logarithmic [dBVpk=20log(Vpk)]

RefLevel        :   +24dBu      +19dBu/HighPower    +13dBu      +4bBu/LowPower
========            ======      ================    ======      ==============
XLR1/2 (in/out) :   17.4/24.8   9.77/19.8           4.90/13.8   1.74/4.8
TS1/2           :   9.77/19.8   9.77/19.8           4.90/13.8   1.74/4.8
PH3/4           :   n/a         13.8/22.8           n/a         2.45/7.8
PH1/2 with dual phones mode (and plugged in):
PH1/2           :   n/a         13.8/22.8           7.00/16.8   2.45/7.8
then XLR1/2 and TS1/2 change to (unless muted via Mute Option):
XLR1/2          :   n/a         9.77/19.8           4.90/13.8   1.74/4.8
TS1/2           :   n/a         9.77/19.8           4.90/13.8   1.74/4.8
(+24 setting lost on XLR)

PH1/2 and PH3/4 are replaced in balanced phones mode by:
PHBL1/2         :   n/a         27.6/28.8           n/a         4.90/13.8

We see the possible voltages corresponding 0dBFS can vary in a range from +4.8dBVp to +28.8dBVp, a 24dB span.

For the analog outputs we have a set of 8 possible 0dBFS equivalent dBVpk values:
4.8, 7.8, 13.8, 16.8, 19.8, 22.8, 24.8, 28.8.

Any applied digital scaling to the analog inputs (trim gain) must be factored in for the 0dBFS marks. When it is set to, say, +2dB@L and +3dB@R their 0dBFS marks must drop by 2dB/3dB as well, while the measured and displayed analog voltages are of course still the same.
The analog input 0dBFS point thus can vary from 0dBr to -6dBr in each range, resulting two ranges of dBVpk values,
each in 0.5dB steps: -2.2 to 4.8  and 7.8 to 24.8.
The gap is because +13dBu -6dB of trim doesn't reach into the +4dB range. The higher ranges do overlap by 1dB.

In total there are 5 stereo paths (or 4 when balanced phones is active) to monitored.

What I have in mind is something like the following:

On single scale for all meter columns would be most feasible, that would need a span of 80dB (because of the up to 24dB general difference). Rounding up, this would go from +25dBVpk to -55dBVpk. Scale could be compressed as in the existing meter, first 40dB of range take up some 70% of the column height or so. 5/10/20dB increments (better suited to reading values than 3dB-multiples).

Numerical value of the currently measured peak level in dBVp at the column bottom, 3 significant digits. With a bit of peak-hold, as usual (adjustable peak hold time, including infinite, is yet another topic on the wish list).
Equivalent 0dBFS-Level are marked (area above 0dbFS in a different color, or greyed-out, etc). Analog In needs different markers for L/R because fo the indiviual trim gain. The 0dBFS marks change position when any affecting setting changes, be by user action or by the device itself in Auto Ref.Level modes.

With such a analog level meter screen operation would be much more convenient. Need to dial in 3Vpk (a tad below 10dBVpk) at a given output? Just watch the corresponding meter while turning the volume knob (with "Show Vol Screen Off") until it reads "9.5".

For the analog input it is also obviously nice if one were able to directly read the voltage level without checking the device setting first then doing the manual calculations.