I agree with Audioengr's comments about global feedback vs no global feedback. That is, the amps with global feedback will typically produce more "slam" and tighter bass than the designs that lack global feedback. Part of this has to do with the amps having global feedback having a lower effective output impedance. The drawback to this is that most amps with global feedback will lose midrange liquidity and tend to sound "closed in", "less spacious" and lack separation of notes in terms of midrange and high frequency response. The more global feedback that is used, the more noticeable this becomes.
This is why i've said that Pass amps ( new and old ) sound very nice but lack bass definition and oomph. Even though the newer X series have massive power supplies and great current capacity in the output stage, their circuit design i.e. non-global feedback and slightly higher output impedance is what limits their bass performance.
Too bad we can't get someone like Curl and Pass to work together on designing an amp and then have someone build it with good quality parts. I think that both of these guys are capable of stunning work and the end result would be a pretty fabulous product.
Sim Audio? Never heard any of it. Read some very nice things about their products, but nothing earth-shattering.
MBL 101's??? Good luck. Finding amps that are both good enough sounding and powerful enough to really throttle them as needed may be a life-long task. I wish you all the best and hope you enjoy the journey : ) Sean
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