I just acquired this vintage (60s-70s era) microphone from Maynar. It is presenting a mystery of sorts. It seems to work well, but needs a lot of gain. I've been doing research, and I can find a bunch of info on the CM654d, but NOTHING about the CM654a! A condenser mic should not work at all without phantom power, but the 654a provides a signal unpowered. If I add phantom power, it gives it just a tiny boost, not much. To get a good signal, I have to max out the gain on my interface. It sounds fine. I have not connected it yet to my Trident 80B preamp. I read where these Calrecs are unbalanced, and require a proprietary power supply or a custom built adapter cable in order to use phantom power. This 654a works just fine with a standard XLR. I'm emailing anybody I can find that posted anything about CM654s in the last 40 years. Any expert here know anything about the Calrec CM654a?