Anyone using the Transistor Research LabsM 225's

It is not Class D, although you are correct that regarding heat distribution it resembles a Class D design. Sonically IMO that is not the case.

It is a well known fact that information and specs on TRL components is hard to come by. While Paul Weitzel measures his equipment the main design goal is the end result which is always about the sound. It is also well documented that specs don't always tell the whole story about a particular component, TRL or others.

So with that said from what I've been able to gather the design is biased Class A up to a certain point, then A/B. Another tidbit that I discovered is that from a current draw this amp design is incredibly efficient. The capacitance within the amp also factors in an immense storage capacity for reserve power when required. That in part is why I think many can equate the sound of this amp to a live experience. Transients are amazing and the amp responds in lightning quick fashion.

The amp is dead quiet and the new power supply design is supposed to be the best yet. Not that the old one or the battery power supplies were shabby either. One thing I can say is Paul has an excellent understanding of electricity and power supplies. Also as a recording engineer he certainly has his own understanding and opinions on live sound.

Tvad, I suspect that your suspicions are correct :)

All of the Class D trademarks are present. The sound, the lack of heat, the efficiency, and the price, all add up to scream Class D!

Fiddler, so are you saying that these are Class D amps or that these just sound like Class D amps?

FWIW, I've heard a few Class D amps and while they have sounded very good (especially for the money), none exhibited the sound of my TRL D-225.

I have found the Class D amps I have heard to be very transparent, neutral, and they are very efficient. However, they lacked a very key component IMO to what the TRL offers and that is presenting the music in a very natural life like manner. There could be Class D amps that do this, but none that I have heard. I think its why tube preamps are a good match for Class D amps.

Tvad and others with interest. For some time due to intellectual property concerns the D-225/ST-225/M-225 amps were "locked down" and unable to be opened. Now that those concerns have been addressed the amps innards can be viewed. I was just on the phone with a new Samson owner the other day who gave me a very detailed description of what was inside. From my previous knowledge and experience it was consistent with what I already knew and provided some additional insight on the design.

And what did you find out, Clio?