Fine tuning the system. Where do you start and how do you proceed ?

Tuning by source material is problematic IMO. I have never used a small number of reference recordings to tune my system since this not how I listen. I play all manner or recordings, all genres, all qualities over the long term. If there are shortcomings you'll hear them in time, no reason at all to speed up the process, you'll only go in circles with short term listening with a certain number of reference recordings. Having patience and quit always listening with analytical part of brain is key. Enjoy what you have, the small displeasures may expose themselves over time, only then do you make a change. And never forget one change at a time, too many variables will only confuse.

I just posted this on another thread and think it fits here as well.

I’ve been listening, reading, building, selling, swapping and buying hifi since the early seventies and almost every move has been an upgrade, or at least a noticeable change.  I will never stop reading and listening, but other than changing my DAC, I’m really happy with my current setup. And speaking of the DAC, it’s a Pontus ll and I really enjoy the sound of the R2R sound and would love to hear others, but it ain’t as easy as it used to be.

The Room. Absolutely the most important component in a sound system after your ears.

One thing nice about Agoners is the support of properly treating rooms as a significant sonic issue.

1. The room

2. The setup

3. The gear

However, I have found a significant difference in SQ among recordings. So much so that I grade each one D, C, B, A, A+ based solely on sound quality.

 Almost makes a case for the album making the biggest impact on what you hear.