Full-sounding SS amps (besides Pass)

Hello Peter, unfortunately I have never had a chance to hear your amplifiers - they look great.  I am curious about your design of big stereo amps instead of monoblocks, and also about the "bridged" implementation of your stereo amps - are these true differential amplifiers?  Is there any effect on the input or output impedance of the amps when running them bridged?  Also curious about your use of MOSFET compared to bi-polar output devices.  My experience has been that MOSFET outputs sound softer while bi-polar outputs have provided better dynamics in the amps I have heard, but I am sure these observations have been influenced by more than the output devices alone.

Clayton Audio Class A

taww, I believe Pass uses MOSFETs in his output stages.  The two most recent MOSFET amps I have owned were Lamm's M1.2 Reference monos and the BAT VK500.  The Lamm amps were the best of those two but still sounded a bit soft/rounded in comparison to the three other amps I owned at the time (2 bi-polar amps and a set of NCore monos).  This may have been due to the hybrid design with a 6922 tube or the lower power of 110 wpc compared to the other amps that all provided at least 300 wpc.  You are correct, I should hear some of the newer MOSFET designs for comparison.

I would also like to hear the Gamut M250i (250 wpc) mono amps that use only a single NPN high powered MOSFET per phase (i.e., two per channel).  I am curious whether a single output device would improve clarity and naturalness over having banks of transistors that will never be exactly matched with each other.  However, I am sure there are other trade-offs (pluses and minuses) as with any design, which is why we need to hear the gear rather than purchase based on topology or reviews by others.

Hi Peter and thank-you for the detailed reply.

I prefer the sound of MOSFET output stages - to my ears Bipolar always produce a "lisp" "s" kind of sound.

I know both design and parts selection are important and I have heard the "lisp" type sound with a couple of amps, including Cary's newer 500.1 SS amps (that I simply couldn't live with) but I never had that problem with their older 500MB SS amps that I found to be quite musical and liked much better.  The older 500MBs used Sanken 50 ampere, high current, wide bandwidth bipolar output devices.  My Class A Claytons, which use Motorola bipolar transistors do not have any signs of "lisp" or haze or any other artifact but I am sure the Class A operation bias and large power supply contribute to the sound.

I prefer the conveniences of having monoblocks and I am curious about your choice of really large stereo amplifiers vs. dedicated monoblocks, and whether the sound is affected (or not) by bridging a pair of your stereo amps (such as the mini-Olympia) as a monoblock implementation.  Do the amps provide fundamentally the same sound quality whether they are operated as a single stereo amp or a bridged mono pair?  Are there differences in addition to power output, such as input or output impedance, frequency or distortion characteristics, or other differences between the amps run in stereo or mono?