Nord Acoustics NC500 MKII Dual Mono
Amazing Amp, my new favorite. I like it better than my PS Audio M700s and/or BHK 300.
Competitive class D amp suggestions
I have been Class D fun since a few years ago when i bought my first class D amp. I like the concept, in general, and all the attractive features of this class of amplifiers. I tried 4 different ones, currently i stayed with one of them that i consider to be the best among all four amps. I do enjoy and like it. At the same time, my 5 watts SET amplifier (with more than 100 times higher distortion according to the specs) gives more natural and (surprisingly) notably cleaner sound (THD of the class D amp is 0.001). The soundstage of the class D amp is not so bad but that of the tube one is still better.
I remain attracted by class D amps though.
Any fresh suggestions on reasonably priced class D amps (i mean excluding non-reasonably priced class D amps, e.g., Merrill amplifiers)?
Any comments on non-reasonably priced class D amps are also welcome (so far i was not able to audition many class D amps and am curious if there are some which could really compete with Class A).
223 responses Add your response
The distortion can be quite low! The tricky bit is knowing what is meant by 'warm'; to some this is a bit of extra mid bass energy. I see it as 2nd harmonic and of course it can be both. I think you'll find though if you delve deeper that those comments do not apply to all. Nelson Pass is aware of how distortion affects tonality so he is careful in his designs to make sure he's got a bit of 2nd going on to help out in that regard. |
I have a small update on the LSA GaN 360 Voyager amp. it should have now a bit over 100 hours of burn-in (I used it more than usually in my second system basically leaving it on most of time). I did not note any essential improvements after 80 hours or so. Perhaps, it may still get a bit better. I can say now how the Voyager compares with the Cherry Megaschino in my second system. The sound of Cherry is cleaner, more open, less "forced" and more alive and natural (even with half-working right channel, I adjust the channels taking an extreme balance position). To me, Cherry does not sound like a traditional class D amp, while Voyager sounds like a good class D amp, perhaps the best one I have heard so far except Cherry. No doubt that it is a very good value performance/price. I suggest that Atmosphere and AGD amps may sound somewhat similar to Cherry, but cannot be sure of course. For me, Cherry just sounds like a good class A tube amp, point. So pity that Tommy passed away! Soon I will move the Voyager to my main system. I will let you know about my impressions in a few days or so. @twoleftears and @atmasphere , thanks for additional explications! I did not reilase, from the beginning, that different pics were different harmonics, a very useful image. But now I do not understand what the blue curve stands for.
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@niodari Red and blue track the two stereo channels. In a well engineered component, they should pretty much overlay; more than a little divergence is indicative of a problem with components, construction, design, etc. |
I used the LSA GaN Voyager in my main system for a few days. Not surprisingly, it didn't sound worse in the main system, which is a good characteristic. At the same time, the main system revealed some technical problems related to the amp. I noted this before in my second system as well but I suggested that the problem could have been in the preamp. First, the amp just does not sound well with the balanced inputs - there is a quite notable lack of the middle and high frequencies with the balanced inputs ( i tried two different quality balanced cables). Fortunately, one of the RCA inputs has no such problem. Second, a quite strange thing happens. With both XLR inputs, the left channel is too weak. And with both RCA inputs the right channel is too weak. I mean, even if i stand in front of the speaker, the sound coming from the other speaker is dominant. The preamp in my second system has the balance control, so this issue was somehow "settled" by reducing the volume in the normally sounding channel by about 40%. The T&A DAC/preamp in my main system has no balance control, so it was just impossible to use the amp with either XLR or RCA inputs. Then i used the rear switches to put the right channel in XLR and the left channel with RCA modes . This was the only way to achieve a more or less balanced sound. Third, i think the amp has some phasing problem. Apparently, it is made out of phase. But when I swapped the positive and negative speaker outputs, the amp remained out of phase. Perhaps, this is not a big problem but something may also be wrong with this. Based on my small experience with the combined XLR-RCA auditioning in my main system (thanks to the rear amp switches that permitted me to use such an option), i think there is nothing particular to complain about the sound quality of the amp (judging analytically). At the same time, there is no point in comparing it with my SET tube amp that just sounds more real, full and alive. This can be subjective. But perhaps, not. Just take one of the CDs I used to compare the SQ of the two amps. It is Keith Jarrett's "Buy buy blackbird" (hey @jjss49 !). It is a particularly well recorded CD. Although it is a studio album, one can feel the studio environment and the musicians on each of the instruments, just as if it were a live recording. The SET amp gives this feeling, the Voyager does not (so far as it is now). Perhaps, the Voyager may still improve (it should have about 110 hours of burn-in). I will be able to judge once I get it back from Underwood Hi FI. I am going to ship it for repair today.
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Here's the measurement of the Technics SU-G700M2, which may not be exactly a class D amp, or a GaNFet amp, but which is something close.
As you'll see, some of the higher order harmonics are higher than one often sees, and normally you only want to see the second and third harmonics around that level. John Atkinson commented: "The fifth harmonic in both channels, the seventh harmonic in the left channel (blue trace), and the ninth harmonic in the right channel (red trace) were almost as high in level as the second and third harmonics. Although these harmonics are low in level, lying between –80dB (0.01%) and –70dB (0.03%), they could be audible at high listening levels in the region where the ear is most sensitive." |
@twoleftears , I wonder how this integrated amp sounds with this speaker impedance correction feature. E.g., the distortion at higher order harmonics (the pick at 1k and the following ones at 2k etc) is considerably higher than that of the first, 2nd and 3rd order harmonics, they should be audible. Given that, it is really interesting how this is reflected on the SQ. The diagram is "unusual" also because it shows a big difference between the two channels where a little distortion is observed in the blue channel as there are only two blue picks. |
For the Atma-sphere class D amp: Is a preamplifier necessary if only connecting a streamer/DAC to it? The streamer/DAC has it’s own volume control (if I want to enable it). Lumin S1. Someone I came across (Ocean) mentioned this class D amp is definitely worth checking out. Also, which preamplifiers are recommended for it (that have a remote)? Other than heat and efficiency, what do you think are the pros/cons of moving to this amplifier from an 805 tube amp (Line Magnetic LM-805ia)?
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@veerossi The designer of the Atma-Sphere GaN amp @atmasphere is on here regularly and hopefully he’ll chime in here with some very helpful suggestions and insights. I believe he now uses his new GaN amp in his own system even over his very highly-regarded OTL tube amps so that may give you a clue, but hopefully Ralph can add more meat on the bones here for you. |
If you will decide to try Atma-Sphere class D amp, you may start to control it with the volume control of your DAC of course. Then you will see if you like the result and then think of a preamp (I have been using a passive preamp with class D). I think the amp is worth of trying and it comes with 15 days of trial (I ordered it just recently). |
Most digital products can drive it directly with ease.
Its my opinion that the specs listed on the Line Magnetic website are suspect. At such high power levels its very hard to make an output transformer that will support that kind of bandwidth and be SET at the same time. At any rate, you'll likely appreciate the extra power, and if you are using a high efficiency speaker you'll appreciate the lower noise floor of the class D as well. My speakers are 98dB and I have to have my head in the midrange horn to hear any noise from the amps at all. That translates easily to better low level detail, assuming that the amp has all its other ducks in a row. Its not going to be as lush but its not dry. It won't be as lush because its distortion is so much lower. The advantage is there is more musical detail and it does this without brightness. Distortion obscures detail, and its a simple fact that whether they admit it or not, before the onset of clipping nearly every SET made makes about 10% distortion. What this means is that any any power level an SET can make, the class D is going to be well over 2 orders of magnitude lower distortion- and so at any power level will offer more musical information. Its not dry because the distortion it makes is very much like that of a tube amplifier- with the 2nd and 3rd harmonics being far more prominent than the higher orders, but of course all at a much lower level than you can get from a tube amp. That is why I ended the last paragraph the way I did- this stuff is easy to hear. |
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Today is a remarkable day in my audio hobby realm - I received a new pair of Atmosphere Class D monoblocks, sent with a care. I plugged in them a few hours before I started to audition them. During the first few minutes of auditioning, my initial impression was the presence of solid low and mid-low frequencies, perception of body and space and lack of mid-high and high freqencies. The latter issue somehow disappeared relatively soon. The amplifier is in its first 2 hours of break in now. I'm already enjoying the sound and I feel that it will get gradually better. I think there is a lot of more to explore with these monoblocks. I will carry out a more substantial analysis, also comparing the amplifier with a few other ones that I'm using after I return from my trip. I hope this will happen in about 3-4 weeks. Stay tuned. |
Just an update on my earlier post on my LSA Voyager GAN 350 map. Mr. Walter from Underwood hifi was so kind to replace it with another new one. So far the new one works without showing similar problems. Walter has also recommend an SPL Elector SS preamplifier, which I think is a good match, it compensates a bit a lack of the body and "inanimateness" in the sound reproduction of the Voyager. |
I’m very fond of the heavily modded Trends TA10.1 I use in my main system. With a nice linear power supply, it sounds marvelous driving the 500 to 20KHz range in my trip-amped, very high sensitivity system. If you don’t need much power, that TA2024 chip has something magical, somewhat closer to SET sound than the vast majority of other class D amps. Swap a few passive components inside, by-pass the volume control (there's a switch inside on the pcb), use it with a nice preamp and feed it some clean 12V, it really is lovely. I have zero experience with the higher end, more modern offerings but have a few small class D with various chips, some of them using great components, but they fall flat on their face compared to the old Trends amp. |
@rolox Thanks for your post. Looks and sounds interesting. Would be nice to try it. |
My 2 class Ds are EVS 1200; dual mono, IcePower AS1200 modules (no longer made) and a LSA Voyager 350 GaN fet amp from Underwood HiFi, which occasionally come up on the used market. Great deal of you're patient, then send it to Tweak Audio for big improvement over OEM, or Underwood has a cool amp based on IcePower AS2 1200, module. Retro design with cool looking meters: On sale now |
