I am owner of the Classe thirty and zeventy combination. The preamp has a dark sound due to the limited frequentie reponse ( 20 khz ), you can solve it by removing 2 styroflex capacitors , the frequentie response is than about 300 kHz, but now you can hear more problems.
The powersupply has as stabilizer 7815 and 7915 you can change these to 317 and 337 with some added electronics.
Change the powersupply elco,s and do not use the ground off the circuitboard but bring that side of the elco with a wire to the transformer middle ( star ground ). and change 2 opamps in opa 627. I must say , it sounds very good. Huib
The powersupply has as stabilizer 7815 and 7915 you can change these to 317 and 337 with some added electronics.
Change the powersupply elco,s and do not use the ground off the circuitboard but bring that side of the elco with a wire to the transformer middle ( star ground ). and change 2 opamps in opa 627. I must say , it sounds very good. Huib