I keep doing this to myself. Every couple of years a new class D amp shows up with a new buzzword attached to it, and every couple of years I convince myself that this is the one that finally cracks it. This time the buzzword was GaN, the amp was the SMSL PA200, and once again I’m writing up the results of what is turning into a very expensive education. Some people learn from the first three class D amps that didn’t click with them. I am apparently not one of those people.
What the PA200 actually is
Before I get into how it sounds, a quick rundown of what’s under the lid, because it matters for the rest of this review.
Infineon GaN FET output stage, switching up to 1MHz
Stereo mode: rated around 85W into 8 ohm, up to roughly 160W into 4 ohm per channel via RCA
Mono bridged mode via XLR: up to around 400W into 4 ohm from a single unit
TI PGA2311 chip handling volume control in the analog domain
Dedicated switching power supply, aluminum chassis, remote control
THD+N specified in the 0.003% range
On paper this is an easy amp to be excited about. GaN is supposed to be the thing that finally lets class D amps switch fast enough and clean enough that all the usual complaints about the topology quietly go away. That was my hope going in, and it’s worth saying clearly up front: it didn’t happen. Not for me, not in my system.
The sound, in short
The PA200 is very clean. I want to give it that credit before I start picking it apart, because it earns it. Noise floor is a non-issue, there’s no grain, no obvious digital nasties sitting on top of the signal. If your definition of a good amplifier begins and ends with “low distortion, wide bandwidth, dead quiet background,” the PA200 will make you happy.
But clean isn’t the same thing as involving, and this is where the amp lost me. It’s clean sounding, but soulless. Music comes out correct and comes out cold. I kept waiting for a track to grab me the way it does through my tube gear, and it just didn’t happen. Everything is present, nothing is missing on paper, and somehow the whole is less than the sum of the parts.
Topology and feedback: PA200 vs NC502MP
This is the part I actually find interesting, because it’s not just “GaN vs silicon,” it’s a real difference in how the two designs use feedback, and I think that difference explains a lot of what I’m hearing.
The Hypex NC502MP, which I’ve spent a lot of time with, uses a deep, multi-order feedback loop that wraps all the way around the output LC filter, not just around the modulator. That matters because the output filter is where a class D amp’s frequency response starts drifting depending on the load it sees. By closing the loop around the filter itself, NCore keeps the response flat and largely load-independent, and that’s a big part of why NCore-based amps measure the way they do and why their treble tends to stay so well behaved across different speakers.
The PA200 doesn’t do this the same way. From what I can tell working through it in my own system, the feedback is a shallower loop that isn’t wrapping the full output filter the way NCore does. GaN devices let SMSL push switching frequency much higher than a typical silicon class D design, which on its own is a real advantage for reducing switching noise and improving raw distortion figures. But faster switching devices don’t automatically buy you the same load-independent, filter-inclusive correction that a design like NC502MP achieves through its feedback architecture. The two amps are solving different parts of the same problem: GaN attacks the switching stage itself, NCore’s feedback attacks the whole signal path including the filter. They’re not interchangeable solutions, and you can hear it.
Where it actually shows up
The most obvious symptom is up top. There’s a real bump at high frequencies that makes the PA200 sound noticeably bright, almost etched on cymbals and sibilants. I’m fairly convinced this traces straight back to the feedback topology I just described — without a loop that corrects for the filter’s own rising response into a real speaker load, that rise is just sitting there, unaddressed, coloring everything above a few kHz.
That dryness doesn’t stay in the treble either, it bleeds down into the midrange. Vocals and instruments through the midband are technically clean but liveless — there’s none of the fullness or bloom you get from a good tube amp. I’m not asking a solid state amp to sound like a tube amp, that’s not a fair comparison. But I am noting that the PA200’s midrange has a flatness to it that reads as accurate on paper and as uninvolving in the room.
Bass is the one area where I have fewer complaints on a technical level. It’s tight, it’s well controlled, it punches when a track asks it to. But compared to a good class A/B amp, there’s no texture to it — you get the outline of the note and the impact, but not much of the fine grain and decay that tells you what the instrument actually was.
Trying to fix it with a tube preamp
I did what I always do when a clean-sounding solid state amp leaves me cold: I tried to warm it up with a tube preamp ahead of it. It helped a little at the margins, softened the very top slightly, added a touch of body. But it didn’t really change the character of the amp underneath. The PA200 remained very analytical — you could hear the tube stage doing its thing, but the amp itself was still fundamentally the same clinical, correct-sounding device it was before. A preamp can dress up the front of the chain; it can’t undo what the power stage and its feedback loop are doing on their own.
Final verdict
I went into this review hoping GaN would be the thing that finally solved class D’s sterility problem for me. It didn’t. The PA200 is a genuinely well-built, competent, low-distortion amplifier, and if you value measured performance above everything else, it will not let you down on paper. But subjectively, in my room, with my ears, it’s not much of a step forward from the regular class D amps I’ve tried before it. The switching devices changed; the fundamental character didn’t. Same brightness up top, same dry midrange, same lack of texture in the bass, just with a fancier transistor doing it.
So, GaN didn’t fix it, at least not this implementation of it. I’m sending the PA200 back to the shelf of “interesting but not for me” amplifiers, and I’ll probably be back here in a year or two, doing this exact same thing with whatever the next promising class D topology turns out to be.
I keep doing this to myself. Every couple of years a new class D amp shows up with a new buzzword attached to it, and every couple of years I convince myself that this is the one that finally cracks it. This time the buzzword was GaN, the amp was the SMSL PA200, and once again I’m writing up the results of what is turning into a very expensive education. Some people learn from the first three class D amps that didn’t click with them. I am apparently not one of those people.
What the PA200 actually is
Before I get into how it sounds, a quick rundown of what’s under the lid, because it matters for the rest of this review.
On paper this is an easy amp to be excited about. GaN is supposed to be the thing that finally lets class D amps switch fast enough and clean enough that all the usual complaints about the topology quietly go away. That was my hope going in, and it’s worth saying clearly up front: it didn’t happen. Not for me, not in my system.
The sound, in short
The PA200 is very clean. I want to give it that credit before I start picking it apart, because it earns it. Noise floor is a non-issue, there’s no grain, no obvious digital nasties sitting on top of the signal. If your definition of a good amplifier begins and ends with “low distortion, wide bandwidth, dead quiet background,” the PA200 will make you happy.
But clean isn’t the same thing as involving, and this is where the amp lost me. It’s clean sounding, but soulless. Music comes out correct and comes out cold. I kept waiting for a track to grab me the way it does through my tube gear, and it just didn’t happen. Everything is present, nothing is missing on paper, and somehow the whole is less than the sum of the parts.
Topology and feedback: PA200 vs NC502MP
This is the part I actually find interesting, because it’s not just “GaN vs silicon,” it’s a real difference in how the two designs use feedback, and I think that difference explains a lot of what I’m hearing.
The Hypex NC502MP, which I’ve spent a lot of time with, uses a deep, multi-order feedback loop that wraps all the way around the output LC filter, not just around the modulator. That matters because the output filter is where a class D amp’s frequency response starts drifting depending on the load it sees. By closing the loop around the filter itself, NCore keeps the response flat and largely load-independent, and that’s a big part of why NCore-based amps measure the way they do and why their treble tends to stay so well behaved across different speakers.
The PA200 doesn’t do this the same way. From what I can tell working through it in my own system, the feedback is a shallower loop that isn’t wrapping the full output filter the way NCore does. GaN devices let SMSL push switching frequency much higher than a typical silicon class D design, which on its own is a real advantage for reducing switching noise and improving raw distortion figures. But faster switching devices don’t automatically buy you the same load-independent, filter-inclusive correction that a design like NC502MP achieves through its feedback architecture. The two amps are solving different parts of the same problem: GaN attacks the switching stage itself, NCore’s feedback attacks the whole signal path including the filter. They’re not interchangeable solutions, and you can hear it.
Where it actually shows up
The most obvious symptom is up top. There’s a real bump at high frequencies that makes the PA200 sound noticeably bright, almost etched on cymbals and sibilants. I’m fairly convinced this traces straight back to the feedback topology I just described — without a loop that corrects for the filter’s own rising response into a real speaker load, that rise is just sitting there, unaddressed, coloring everything above a few kHz.
That dryness doesn’t stay in the treble either, it bleeds down into the midrange. Vocals and instruments through the midband are technically clean but liveless — there’s none of the fullness or bloom you get from a good tube amp. I’m not asking a solid state amp to sound like a tube amp, that’s not a fair comparison. But I am noting that the PA200’s midrange has a flatness to it that reads as accurate on paper and as uninvolving in the room.
Bass is the one area where I have fewer complaints on a technical level. It’s tight, it’s well controlled, it punches when a track asks it to. But compared to a good class A/B amp, there’s no texture to it — you get the outline of the note and the impact, but not much of the fine grain and decay that tells you what the instrument actually was.
Trying to fix it with a tube preamp
I did what I always do when a clean-sounding solid state amp leaves me cold: I tried to warm it up with a tube preamp ahead of it. It helped a little at the margins, softened the very top slightly, added a touch of body. But it didn’t really change the character of the amp underneath. The PA200 remained very analytical — you could hear the tube stage doing its thing, but the amp itself was still fundamentally the same clinical, correct-sounding device it was before. A preamp can dress up the front of the chain; it can’t undo what the power stage and its feedback loop are doing on their own.
Final verdict
I went into this review hoping GaN would be the thing that finally solved class D’s sterility problem for me. It didn’t. The PA200 is a genuinely well-built, competent, low-distortion amplifier, and if you value measured performance above everything else, it will not let you down on paper. But subjectively, in my room, with my ears, it’s not much of a step forward from the regular class D amps I’ve tried before it. The switching devices changed; the fundamental character didn’t. Same brightness up top, same dry midrange, same lack of texture in the bass, just with a fancier transistor doing it.
So, GaN didn’t fix it, at least not this implementation of it. I’m sending the PA200 back to the shelf of “interesting but not for me” amplifiers, and I’ll probably be back here in a year or two, doing this exact same thing with whatever the next promising class D topology turns out to be.