[hawkeye99]

I have A/D/S 910 speakers that go down to 28hz. 93 sensitivity and 4 ohms. I'm using the 2B. Listening at between 70 and 80 decibels which isn't real loud.The amp barely gets warm. I think it sounds pretty good. I'm wondering if I would notice much of a difference with the 4B.

[RDavidson]

I think you might hear a difference, primarily in bass control, but at your typical listening levels I'm only guessing. On the other hand, sometimes simpler is better......sometimes MUCH better. With the extra power in the 4B comes extra circuitry and complexity.....BUT, the 4B is perhaps one of the best values in SS amps, and has been in production a LONG time. It may have refinement beyond just bass control over the 2B in your setup.
If you can, you should just try to get an in-home audition and judge for yourself.

[Grit]

I'll share my recent experience between a 9B-SST2 (new, ultimately with 100+ hours of break-in) and a 4B-SST2 (2012, certainly broken in).

My speakers are Aerial Acoustics 7T's. They are rated at 89 db/1w/1m with a 4 ohm nominal and 3 ohm minimum load. The short version is that, even at low (60-70 db) volumes, the 9B did not sound as good as the 4B. After much reading and emailing both James Tanner (Bryston) and Michael Kelly (Aerial), it seems the 9B just doesn't have the audio torque to drive my speakers the way I prefer.

What *I* heard was guitars sounding tinny or metallic when the pick first struck the strings. Bells, triangles, etc. sounded shrill in their initial attack. The 4B had none of those problems. With the 9B, I found myself focusing on imperfections in the music. With the 4B, I lost myself in the music and found myself tapping my toes and bobbing my head. That is my goal: get lost in the music.

It's my understanding that what I heard was the 9b straining to provide enough power to properly handle the transients, which can take a TON of immediate power, above and beyond what you'd expect. It makes sense. Kind of like stomping on the gas when the car is at a dead stop. If your engine has enough torque for the weight of your car, you'll fly forward. If not, you'll slowly accelerate up to speed. Transients seem to be the stomping on the gas from a dead stop. Decay seems to be more like applying power after you're already moving at the desired speed.

I can also tell you the 9B got hot. Really hot. It wouldn't burn your hand, but you couldn't leave your had on it indefinitely. And that's with forced air blowing over the 9B.

If you can't do an in-home demo and test both amps, I'd suggest you try my toe-tapping test. If you already get lost in the music, I'd suggest the 2B is a great match for your A/D/S 910's.