The Krell Ibias accounts for load impedance, the old sustained plateau bias did not. There really aren’t any amplifiers made that can actually double the wattage when impedance is halved, not even in class A/B. The manufacturers just underrate the 8ohm power spec to accomplish this.
If they do so I am surprised. We like high stated power in audio and cars.
M400’s with OREA Indigo feet. They are 1-1/8 inch high, and the stock feet are 3/4-inch high, so I left the stock feet on. The amps are still settling in and going through a 24 hour warm up cycle.
There is an improvement in discerning details of multiple vocals or instruments. With the M400’s better resolution, I could understand all the words on several songs that in the past were just not clear enough to figure out. That alone was a big win. Quick snare drum hits and cymbal extensions and shimmer are now exceptional.
I guess you have never noticed the measurements in stereophile, quite a few amplifiers that claim double the wattage when impedance is halved, when measured have quite a bit more wattage into 8ohms than the spec sheet claims.
No claim that they remain in class A. Just sayin’.
Doesn’t matter if class A or class A/B no amplifier can double it’s wattage when impedance is halved at full power output.
…but not at rated distortion levels.
Planning ahead I am trying to decide between the S200 and S400 amps. My speakers currently are reasonably efficient @ 88db / 4ohm (floor standing Sonus Faber Sonnetto III G2), and my room is small/medium sized. So I think technically the s200 will be adequate, but is there any reason why I shouldn’t get the s400 for future proofing? Does the extra Class A on the S200 make it worth considering for my needs over the S400? Especially thinking to the future where I may have a bigger space and or less efficient speakers, but the best sound NOW is definitely most important. Just wanna make the best choice.
That depends on the amp. The Levinson 534 is specified at 250 watts into 8 and 500 into 4. It measures over 300 into 8 and 550 into 4, at the specified distortion levels. But the wording sounds better for doubling the power from 8 into 4 ohms.
Chris B., almost as an aside pointed out that the S200 has higher class A output and one might consider that a better match for the FR20’s.
I would generally recommend the S200 for the kind of speaker system and room you’re describing.
Thanks Chris, I really appreciate the input. I was thinking the same. My concern though is thinking to the future if I move to a larger space. If the s200 and s400 will both be great with my current setup but the 400 gives me more future expansion I would consider that, but if the 200 will sound significantly better in my current system I will 100% go that route.
Buy for today; tomorow is another day.
i am afraid that the S400 is going to sell the most of any of the products but is actually has most compromises of the four designs (trying to pack in twice as much “stuff” in the same chassis and heatsink). It really should be the one we sell the least of but we have kind of trained people that they need more power then they actually do by making our best sounding amps the more/most powerful ones in the past.
My personal advice - though just an opinion like anyone else’s - is that you will be 100% happy with an S200 and, if you ever move to a large space and need to drive more demanding speakers, it will likely still be great but you can also choose trade it in on a pair of monos down the road.
Hey Chris — seriously appreciate you jumping in on this! I’m honestly really excited to see how these amps turn out.
I’ve been all-in on PS Audio gear for a while now. I picked up the PMG Preamp and 512 DAC earlier this year. Wow, so far the DAC has made the biggest impact. The preamps, not quite fully burned in yet. Now I’m looking to trade in my pair of M1200 monoblocks. I’d love to upgrade to another set of killer monos down the road… just not quite in the cards at the moment.
For anyone who’s had a chance to hear the new PMG Signature Power Amplifiers (M400, S400, or S200), I’d love to hear your thoughts—first impressions, pros/cons, anything that stood out. .
Peace & Blessings
I am listening to the PMG preamplifier and the two M400’s on FR-30’S with 3 F12 subwoofers using Shunyata Omega and FRR cables with Aurender SA30SA and Berkeley Reference 3P DAC right now. The M400’s really brought the system all together 
. Since you already have PMG pre etc. you owe it to yourself and should not even hesitate. I simply can’t describe the pure enjoyment I have with this. I literally have tears hearing songs I have listened to for 50 years that never sounded like this on any system.
If anyone is curious, in my room, a 35 setting on the PMG preamplifier into the M400’s is about 80 dB at my listening spot, 40 is mid 80’s, 45 is low 90 range, and if you turn it up to 50 it hits 100. For rock, I am really happy in the 37 to 43 setting. They easily deliver any volume a rational person would ever want.
What is this mythical “rational person” to are referring to? 
Someone who can still hear details.
What is the size of your listening room. And how far away do you sit from your FR 30s