-6 dB after connecting output to input on the Scarlett

[GL1zdA]

I have a Scarlett 4i4, and I'm trying to measure something. I wanted to calibrate REW and what I don't understand is that there's a 6 dB difference when I connect the output of the Scarlett to its input. I'm using a short TRS cable, I've tried the same with a TS cable and the difference is 12 dB, which I assume means the TRS cable works as expected. The "Output" knob on the Scarlett is set to the max (0 dB), there is no gain on the inputs (again, 0 dB). I'm attaching screenshots of the software which hopefully explains, what I mean.

 

[Sokel]

Some interfaces follow system's level even when put to ASIO, have you check Windows panel for playback and recording?

 

[staticV3]

Hi @GL1zdA! Welcome to ASR.

There's no rule that says an audio interface's maximum output voltage must match its maximum input voltage, so a discrepancy like that is entirely expected:

 

[GL1zdA]

Some interfaces follow system's level even when put to ASIO, have you check Windows panel for playback and recording?

I've checked it and it looks fine. I booted Windows just make sure it works that way with "supported" drivers, but I normally use Linux and the results are exactly the same.

Hi @GL1zdA! Welcome to ASR.

There's no rule that says an audio interface's maximum output voltage must match its maximum input voltage, so a discrepancy like that is entirely expected:
View attachment 474014

Thanks, I totally missed that. I think I'm starting to understand one part of it. What I see is dBFS and 0 dBFS on the input means +22 dBU and on the output +16 dBU, right? Now, my question is: should I target +4 dBU or any other value when doing measurements? Should I target it when recording another source (making sure the source doesn't exceed +4 dBU)?

 

[staticV3]

Now, my question is: should I target +4 dBU or any other value when doing measurements?

Depends on what device you're measuring, and how you measure it.

 

[GL1zdA]

Depends on what device you're measuring, and how you measure it.

First, I want to measure the Scarlett itself.

 

[staticV3]

First, I want to measure the Scarlett itself.

AFAIK, there is no standard measurement voltage for Loopback tests, so you can choose at your own discretion.

As for measuring the DAC and ADC individually, take a look at Amir's interface reviews for guidance.

Once you've set the DAC to the desired voltage (multimeter highly recommended), play around with the input gain to minimize noise and distortion from the ADC.

And vice versa