I've ran some test on the differences in loudness with each Quad Dac Mode; Normal, High, and External.
I 'm using a Tenma 72-860 Sound Level Meter, and a pair of Beyerdynamic T1 2.gen @ 600 ohms.
As I said before my T1 is not being recognized as a headphone, but as an external audio device.
I was curious as to what type of volume I was getting on external mode vs the high impedance mode.
I had to trick the V20 into getting to these settings with the T1 by using a 3.5mm female to 3.5mm male adapter while switching between my HD 558 and T5p and then back to the T1 with the adapter still connected to the V20.
I used some continuous pink noise I found on Youtube for the test, and I set the volume at 100% (75 in Quad dac settings)
Decibel readings are in dBA
External Audio Device
Quad Dac on 74.2db
Quad Dac off 72.db
74 db is a fair volume for most music, its loud but still safe and comfortable. Quiet music will sound lacking though.
And there is only a 2db difference between on an off. The audible sound difference is just a slightly fuller sound when its on.
High Impedance
Quad Dac on 80.5 db
Quad Dac off 69.2 db
Now this was disappointing, There's a 6 db gain in volume over the External Mode, This is what I should be getting but I'm not, without tricking the V20.
Its also weird that with the Quad DAC Off I'm getting a lower output than with the External Mode off. So does this mean that even with the Quad DAC off, the V20 is still adjusting the headphone to a small degree?
Normal Impedance
Quad Dac on 67.7 db
Quad Dac off 66.1 db
This provided the lowest output to my T1.
And again the Off setting is different from the High and External Off settings. So the V20 is still adjusting the output somewhat, based on what it thinks is connected even when the Quad Dac is off.
Very interesting, hopefully there will be an update or perhaps an app that will allow us to get full control over the output, especially for situations like mine.
Any how I just thought I'd share.