I just got 2 preamps back from Vladimir, a Nakamichi CA-5 (the mate for the PA-5 preamp), and the Adcom GTP-400. Both had issues. The Nakamichi had noise in one channel through all inputs, and the Adcom lost one channel after playing for half an hour. I didn't have the use of either when evaluating the Nakamichi PA-5 power amp, which I used connected directly to my DAC, using my computer to control volume. It sounded pretty good. I was quite excited to bring the preamps home and really check them and the PA-5 out together, especially since the Nak preamp has an excellent phono stage, with low output moving coil capability (I have a turntable with a low output MC cartridge arriving soon).
Well I connected the 2 Nakamichi pieces, switched the system on and heard noise everywhere. The Nak preamp with another amp sounded as quiet as it had in Vladimir's shop. The Adcom preamp with the Nak power amp was almost as noisy as the Nak preamp. And the kicker: the same noise, but much quieter was present with the DAC connected directly to the Nak amp with the volume high and no music playing (but was something I must have missed with music playing at regular volumes). I'm not crazy, both preamps did have issues that Vladimir fixed, but the Nakamichi PA-5 clearly needs to visit him too. Swapping components in and out to troubleshoot noise issues isn't my idea of a good time. Listening to music is.
These are the kind of problems that make frustrated music lovers run to Best Buy. Resist! The effort of sorting these issues out will pay off.