The "D" in D-225 stood for Dual Mono. Another unique design feature of TRL amps/preamps is the use of a high quality breaker switch in lieu of fuses. When powering on my D-225 you could hear the dual power supplies engage.
In addition to Grannyring's comments about the new power supply I would add that Paul Weitzel has always eschewed negative feedback. Many transistor designs utilize some amount of negative feedback, but not the TRL designs. Paul has also addressed the issue of ground noise in his designs. Another reason these amps are dead quiet.
The Audio Circle thing has been beaten to death. You just have to make your own personal call on that. As evidenced by people like Grannyring and Interlochen who have purchased these amps and whose other components past and present speak for themselves, sometimes you just have to take a chance on things. In this case neither has been disappointed from what I can tell.
In addition to Grannyring's comments about the new power supply I would add that Paul Weitzel has always eschewed negative feedback. Many transistor designs utilize some amount of negative feedback, but not the TRL designs. Paul has also addressed the issue of ground noise in his designs. Another reason these amps are dead quiet.
The Audio Circle thing has been beaten to death. You just have to make your own personal call on that. As evidenced by people like Grannyring and Interlochen who have purchased these amps and whose other components past and present speak for themselves, sometimes you just have to take a chance on things. In this case neither has been disappointed from what I can tell.