Class A Solid State Sound

Generally, there is a small difference between FET type devices and bipolar devices. Sometimes FET devices can have a colored texture to the sound - more of a warm and fuzzy type sonic signature. This is not always the case, but FET does lean this way. The warmth of Pass Labs (and possibly Accuphase) definitely leans this way. I would not say Pass is very warm, but it’s a nice controlled easy listening sound.


Bipolar is usually a lot cleaner sounding (without that warmth influence). Gryphon is an example of this. Sometimes the high bias Class A bipolar devices can present a very smoothed over and liquidy sound (this is also an extreme coloration, but it’s different than the FET warmth). The new Krell sliding bias Class A amps are like this. New Mark Levinson are also very liquidy sounding. There are many others, but I can’t remember them.

@auxinput 
Your description is pretty much what I hear between MOSFET and bipolar or BJT output stages.  BAT solid state amplifiers are another that to me have that soft/warm/fuzzy sound.  The effect is less noticeable in the Lamm hybrid amplifiers I have owned, but still perceptible as a fuller, less distinct and slightly boomy bass presentation, at least to my ears.

audiobrian

High biased push/pull Class-A sound when all is correct, has an ease to it, almost like you need to turn it up.

Complementary output transistors like Bi-Polar’s generally will punch far more current than complementary Mosfets can.

If both are used in push/pull high biased Class-A like these amps you mentioned, you’ll find the Bi-Polar output amp able to drive far more taxing speaker loads, and therefore sound have a lot more punch when needed into those speakers.

Pass and Accuphase use Mosfets and a Gryphon uses Bi-Polar output transistors, on speakers like most all Wilsons ect ect, I would suggest watt for watt the Gryphon’s

Cheers George