@fleschler most of the upgrades in general are in the power supply section. Upgrading to nichicon or audio note capacitors. Then signal path resistors mostly amtrans or audio note non-magnetic resistors now.
Tube rolling is not a upgrade we perform. Our DAC and preamp began as 101D direct heated triode tube products. Lampizator was not even offering that sort of product. I do not remember what Grover secret sauce was and I don’t believe that most products we repair/upgrade/modify are not good sounding. They just can use a little benefit from the better parts. We only change the design for products that are in very bad shape and have burnt circuit boards. For the Da Vinci, that was a real mess and we had to fix other repair techs work. We were the only ones that got that unit to work. We also repaired an older Art Audio stereo amplifier that nobody else could repair. Again I will say that my business partner has a masters degree in electronic design. He has been doing this since he was 10 years old. How many people can say that?
I don’t remember the person who posted about his Lamp upgrade. Don H (not sure if I can post his last time without his permission). But the power supply and some resistors were upgraded with better parts and that upgrade produced fantastic sound to his unit. We were impressed with it.
We also did a Cary SACD/CD players maybe 306S. Over one hundred parts we swapped out if I remember correctly. We did this for someone and the results were so great, I purchased the same model and upgraded it for myself. So we are always learning and wanting to improve our own sound.
Thanks for posting.

