Active speaker is a speaker with power amp inside, fixed amplification ratio.

Your dac work as a pre-amp to control the volume (output level)

Your PC is the audio source, say music files, if recorded correctly, it plays at full volume without problem.

So, turn down your dac volume with the big middle knob to minimum first, play a music file at the PC with full volume, then turn up the dac volume slowly to reach the desired listening level.

The following with [x] means a button, or the encoder which can press/turn.
Press [SETUP] turn encoder [1] until the display first line shows "Options". turn encoder [2] until the display second line shows "Display", press encoder [2] to reach "Hor. Meter" and turn it again to select "Dual", press [SETUP] again to exit the menu. After you done this, the horrizontal meter shows the source volume (level) with two thin lines, the thicker in between are the output level. Both vertical meter and horizontal meter dance with the music.

Read the manual, understand the dac menu and buttons function, come back later, so that we can have the same common language to assist you more step by step.

Thank you. Johannes AU.

What does this procedure do?  What is the purpose of it?

:The following with [x] means a button, or the encoder which can press/turn.
Press [SETUP] turn encoder [1] until the display first line shows "Options". turn encoder [2] until the display second line shows "Display", press encoder [2] to reach "Hor. Meter" and turn it again to select "Dual", press [SETUP] again to exit the menu. After you done this, the horrizontal meter shows the source volume (level) with two thin lines, the thicker in between are the output level. Both vertical meter and horizontal meter dance with the music.

I‘d prefer a pair of passive attenuators for a better signal integrity:
In your country:

The one from Shure, £ 110.00 for a pair:
https://www.dv247.com/en_GB/GBP/Shure-A … 003805-000

The JTS, £ 37.00 for a pair:
https://www.dv247.com/en_GB/GBP/JTS-MA- … 015915-000

But if you like the active SPL Monitor controller better it would do the job too.

It works a bit against ADI-2‘s design, you can read about the disadvantages in the manual page 65:

Excerpt:
31.13 Digital Volume Control

The ADI-2 DAC deliberately avoids an analog level adjustment by means of a potentiometer. Its digital version surpasses an analog one in practically every conceivable point. Typical disadvantages of setting with potentiometers:

Synchronicity errors lead to panoramic shifts and significant volume deviations left / right, in particular near the end points of the adjustment range.

In the middle setting range, there is an increased crosstalk and changes in the frequency response. Changes in the frequency response also occur at the end regions of the adjustment path.

The setting range for optimum volume adjustment is often too small, or at the lower or upper end of the potentiometer's adjustment range.

Non-reproducible settings (except 0 and 11).

Higher THD/THD+N. A point well known to measurement technicians. As soon as an analog potentiometer is in the signal path, the unstable contact between wiper and resistive track causes noise, which contains both THD (distortion) and N (noise), even in the stationary state. Thus the -110 dB of a DAC quickly gets reduced to for example -80 or -70 dB.

From reading articles on the web, the answer in my case seems to be to have the Windows laptop usb source volume and connected genelec speakers, as loud as possible, and the dac digital volume set as low as possible, on the basis that the latter will retain its resolution better at lower volumes than the genelecs.

Kind of true, set to 100 %, not above!

Wrong in general, and makes absolutely no sense for your case.

Your sub has no volume control.

So, with Genelec’s volume controls you have to set the balance to the Sub.
So don’t change that, or you will change the bass amount.

Anyway, Genelec’s Volume setting has no influence on their resolution, only their loudness is affected.

Next:
Of course any DAC has it’s best Signal to Noise Ratio and highest resolution when it makes full use of it’s dynamic range, say, when the signal is high.

Opposed to others DACs, ADI-2 Pro uses a digital volume control, as described some postings above.
If you dial down to -40 dB, the DAC chip works at 1/100 of it’s normal level.
(Due to the clever “Auto Reference Level” function in reality the situation is better, but still about 1/10 of normal).

“Auto Reference Level’s” optimum working range is for volume settings between 0 dBr and -24 dBr.

Get the passive attenuators to fit the Volume dial range to your listening level, and you’re done!

For the JTS, £ 37.00 for a pair, is money very well spend:
https://www.dv247.com/en_GB/GBP/JTS-MA- … 015915-000