I don't understand this 6 dB gain

[sten]

Hi all

I am running the QA40x software version 1.194 on Linux with Mono. In this self-test, I am shorting the left inputs and outputs. According to the measurements, I’m outputting a sine wave of amplitude -6 dbV, yet the diagram shows 0 dbV and consequently the gain measurement shows 6 dB:

Now you may think that this is because I specified an external gain of 6 dB, but that it not so, as you can see here:

I don’t understand this behaviour. Could someone explain?

Cheers

Stephan

[MarkT]

The output level is given for a single-ended output - if you use full differential output you’ll see twice the voltage, hence the apparent gain of 6dB.

In the (relatively common case) of using a single ended output into an amp and sensing the output differentially to output ground no correction is needed, which I think makes sense.