How do i gain match 2 digital sources?

How do i gain match 2 digital sources for better use of the volume range at a low budget?

Marantz PM6006 with a new modern quality dac built in

Pc and very old cdplayer 25 years or more, i want to connect them to my amplifier digitally

I want to gain match them to my turntable as a reference since i can do it from my casettte deck, cdplayer (only works on the analog output) and also from my pc since i use a mackie onyx usb soundcard with volume knob but not from my turntable.

If i use the built in dac i my amp i would only need to use an optical cable from my pc and cdplayer to my amp (or the digitally gain control unit) and can return my usb soundcard or sell it.

I would also get better sound from my cdplayer which is old.

When i connect my cd player with an coaxial cable to my amp the sound is way to loud, already at 9 o’clock it’s loud, instead of 12 o’clock.

What do i need?

How do i do it?

you really don’t want to play with volume in the digital domain, your just throwing away bits.
So for the best results you want the volume change after the DAC at the very least.
But then from what I can see you’d need a DAC with multiple outputs (don’t know of any) or multiple DAC’s with volume control or passive preamps.

If you can live with tweaking volume in the digital domain you might be able to do it with something like the MiniDSP, but I really don’t have enough experience with it.

MinimServer are surpose to do volume level adjustment losslessly. (havn’t tried it)

I know a little about the Minis dsp HD (Zeos pantera) but as i know it’s not cheap and i want to use it with my cdplayer independent of my pc (use it with my cdplayer without having to use my pc).