Following on, at 200 Hz the output impedance is 10x better with nCore, but the absolute figures are tiny. The difference in output between a high and low impedance speaker is less than 0.01 dB.
Most "normal" speakers get very difficult to drive in the bass, not the treble, so for these owners, I think nCore and ICEPower are equivalent and subject to personal preference.
If you have an ESL though, I would really expect the nCore to over perform.
Best,
E
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So, let’s get into some meaningful spec-manship. Let’s compare the frequency response, and output impedance (8 / output impedance = damping factor) of ICEPower and nCore to see about what could matter with different speakers. Here are the source docs I start with: Ncore docs: https://www.diyclassd.com/documenten/download/860ICEPower : http://www.icepower.bang-olufsen.com/files/solutions/icepower250aspdata.pdfI’ll use a couple of examples. My own custom built speakers which have around 9 Ohms of impedance at the top octave, and ESL’s which are basically giant capacitors, and murderously low impedance at the top octave often near 0.3 Ohms.
I should point out most SS amps have coils at the output to protect
from hyper-sonic oscillation. This coil acts as a low pass filter and will cause the frequency response to droop at the top octave. This is not by
itself unusual or ONLY about Class D amplifiers.
Using a "normal" speaker like mine let's examine how the output impedance changes response at the 20kHz mark: nCore: -0.003 dB ICEPower: - 0.3 dB 0.3 dB isn’t inaudible.... but VERY subtle. Below this, in the bass where many speakers get difficult to drive, there’s only tiny differences in response. Certainly better than most tube and zero feedback SS amps. This is a small difference which fits well within the idea of "system matching" an amp to personal preferences, speakers and room tuning. But let’s take an extreme case of an ESL which has around 0.3 Ohms in the top octave: nCore: -0.08 dB ICEPower: -6 dB This is a case where the nCore could make a very significant, audible difference when playing the same speakers. My point to this is, based on specs, both modules will perform very well with normal loads. Any differences in the top octave may be inaudible, or useful. This is one example of where I think specs and technology can help us understand how to match an amplifier with our system better. Best, E |
I'm just saying that I am open to the possibility that different Class D amps, like their linear counterparts, may sound different on different speakers.
But if this IS true, I won't attribute it to Class D vs. linear.
I believe nCore's do have exceptionally low output impedance across the frequency spectrum compared to ICEPower so I'm not surprised. :)
It also depends where your speaker is difficult to drive. With my speakers, there's unlikely to be much difference since they are easy to drive. ESL's however have the hardest trouble at the top end. I would not be surprised if the difference between an nCore and ICEpower module was more measurable/audible with them.
Other speakers, like say Focal's with double woofers, are hardest to drive in the bass, a place where both nCore and ICEPower excel.
Best,
E
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Hi @guidocorona
The general principles that a higher switching frequency with better transistors yields lower distortion and higher efficiency is not really in question.
I question the audibility of anything measurably better than the current state of the art from ICEPower, nCore or Pascal. I question the importance of 0.03% distortion vs. 0.003% vs. 0.00000001%. Having a baking scale that measures in femto-grams does not help you bake a better cookie.
If there are audible benefits, I think the answer will be somewhere else. Such as linearity (lack of compression), noise shape or handling difficult to drive speakers (complex impedance curves), etc.
I won’t get excited at all right now over an amp with a high switching frequency, or lower distortion. Especially not at high end prices.
There may be audible differences between the major Class-D technologies, but harping on things I think were solved a decade ago I don’t think will help me find a "better" sounding amp. Maybe a "different" sounding amp though.
Best,
E
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Also, the meters on the Technics SE-R1 are super cool. Wish I could buy the casework alone.
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At $17k a pair? No. No thank you.
I’ve heard current linear amps that were about that expensive and I wouldn’t switch to them either. To me the idea that we need super technology to finally fix the Class D problem just wont’ fly.
Blame my tin ears if you must, but this was solved a decade ago.
Best,
E
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Always fun to talk tech.... but I've been living with dreamy sounding amps for a while now. I don't need my switching frequency increased to have the best.
E
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@georgehifi
Guess I didn't pay enough for them to find the problems Fremer had.
Best,
E
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I wish we weren’t ragging on Pass.... but yeah, my own experience (but in 2 different systems) was that ICEPower ASP was their equal.
Which also, by extension and if I have any integrity, means the Parasound Halo amps I've heard are also very very close.
Best,
E
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Hifidream :
Interesting, very similar to the Yamaha EEEngine I wrote about a little while ago, and therefore similar to the Carver amps too.
Best,
E
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Welcome @whitestix !
I am glad you are finding it informative, I'm learning a lot more about the marketplace, and happy to find so many sharing my appreciation for the latest amps!
Best,
E
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Hi George,
Feed forward in a linear amplifier is very different. :)
In this case, I’m using it more as an analogy or principle rather than a specific circuit design.
While most amplifiers have feedback at the output stage, the Technics does the correction mathematically at the input, pushing the error compensation from the front instead of the back.
For this reason, I think of this as a feed-forward idea, being the opposite of feed-backwards.
Best,
E
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It may not be, but it works totally differently.
In a digital amp the feedback affects the width of the "on" period.
First, I’m not sure that anyone has proven in a linear amplifier why moderate feedback is a bad thing. Second, in class D it is a couple of stages away from the output signal, so whatever arguments you might have made for a linear amp’s feedback I don’t know that they would work at all.
As I understand it, Technics is using more of a feed-forward loop. They analyze the errors with the output stage, and then digitally correct it ahead of time, before the actual power amplifier stage. Talk about a huge amount of processing and signal meddling though. :)
The Technics approach is VERY similar to digital EQ and phase correction if you were to limit the correction to purely electrical, it is identical in theory.
If you go that far, might as well include the acoustic output of the speakers as well and finish the job. :)
Best,
E
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Todd,
If you like tubes, stay with tubes. :) No matter how good the Mytek is, it won’t be a tube pre. :)
Best,
E
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I like it, a line of electronics named after great cheeses of the world.
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Great info @noble100
I don't usually agree with the theme that "Class D is about to get as good as Class A" as I think it has been there for a while.
Linear amplifier distortion can be reduced by feedback, something digital amps may use in buckets.
Where I think the new Technics amps using this transistor will be most interesting is in amp/speaker matching, as the average Class D module is not the current delivering brute that say a giant Boulder or Krell is across the frequency spectrum. Technics has an interesting way of handling it. I handle it by making easy to drive speakers. :)
Best,
E
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It's really interesting to me what great participation one gets when you start the thread off right. :) Thanks to everyone for chiming in.
Best,
E
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@chrshanl37
I think that's an excellent idea. :) Some modules provide supplementary 12V power, so with a little tinkering you may indeed be able to revive them without very much work! :)
You may also want to think about replacing any lights with modern LED equivalents. May help with the power supply situation.
Best,
E
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Todd,
Have you heard the Mytek DAC/preamp combo? They're pretty good if you have liminted number of sources. :)
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You know, one digital-ish amp technology we haven't talked about is Yamaha's EEEngine. It is a hybrid approach, which reminds me of Carver's Magnetic Field and NAD's voltage switching technology. It uses a digital amplifier to provide the + and - voltage rails, but a linear amplifier at the output. http://www.yamahaproaudio.com/global/en/training_support/selftraining/technology/eeengine.jspI've never knowingly heard them, but if anyone is using one let me know. :) Best, E |
Todd,
Remind me please your preamp?
I was a big fan of the old-school CJ preamps. I had thought about getting a modern Cary instead, but man, the press they get about service quality.
I've not listened to CJ pre's since they came out with the ART line.
Best,
E
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I really really like the idea of putting a tube pre in front of these amps, especially with the high-input impedance varieties I've read about.
I often suggested tube pre/ss amp before, so this idea appeals to me a great deal.
If I wasn't 50/50 HT and music I would consider it more seriously for myself.
Best,
E
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@georgehifi
Very interesting! :)
Hexfets..... I seem to remember ... was it Toshiba that invested heavily in them for a while?
Best,
E
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Interesting info on the Technics SE-R1 amplifier from @georgehifi
One thing I thought was particularly interesting (and a lot of work) was the
Load Adaptive Phase Calibration.
All digital amps must go through a low pass filter at the output. This may cause some variability in the high end response based on many things. Modern digital amps with easy to drive speakers should not suffer this very much (especially if they use feedback at the output, shhhhh!)
The SE-R1 takes on the approach of measuring and directly compensating for this at the input instead of using feedback.
This is a LOT of number crunching to put into an amp. Cool ideas for sure.
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@georgehifi
Your link just reminded me of something. One thing I really like the Japanese manufacturers for is power meters. Yamaha (professional), Hitachi, Technics, early Onkyo. Gorgeous analog meters in the 1980’s. I’m very happy to see some of this coming back, even if it is in gear I can’t afford. :)
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Interesting, @georgehifi re garding transistor manufacturing. In 1976 Dr. Leach introduced his paper, Build a low TIM amplifier which transformed, if not codified, what would be linear amplifier design for the next 3 decades. Also 80's were flirting with MOSFETs that promised to behave more like tubes. High input impedance, more linearity, blah blah blah. and some worked out, some worked out some of the time. :) I think James Bonjiorno (spelling?) and Sumo in general were among the early names that were associated with this. But we digress. Well, there is always some technology around the corner, some new way of winding a transformer that promises never-before heard of improvements. 99% of the time, these changes don't pass the test of time, and are forgotten by their own inventors, or fail to make enough of an impression to be adopted by others. There are also a number of amplifiers who end up being door stops once the manufacturer of the super-special magic transistor stops making them. << sigh >> Remember Halcro with their super low distortion, universal accolades? It went under, came back... and now who knows. I guess my point is, we can always look forward to new things, but we can't let that stop us from enjoying what we can get now. :) Best, E |
Guys,
You know I was just thinking about something. If the current crop of digital amps had appeared in the 1980's I think they would have pretty much ended the solid state / linear amplifier market.
The SS amps at the time were, by and large, full of compromises, and consumers were hungry for all things digital.
This did not happen however, the digital amps of the 1990's weren't nearly as good as they are now, and solid state amplifiers also continued to advance to where they are today.
Still fun to think about. :)
Best,
E
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Hi randy-11,
If you mean the multi-channel amps with Hypex/nCore modules, YES THEY DO!
I would just be sure to listen first. I have heard a couple of modern NAD gear and I didn't like it. This is a brand I really encourage you to listen / try out before committing.
Best,
E
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Hi @roxy54
You know, I probably heard the same Class A amps @whitestix heard in the Bay Area and I have to concur. I re-iterate, blindfolded and level matched I don’t think I could tell them apart from the Parasound A23’s. Both are excellent, modern sounding amps via my reference speakers.
Negatives?
The ICEPower 250 ASP modules are in no way euphonic. They lack the utter calmness and dark backgrounds of the very best Ayre or Arcam systems. They lack the juiciness if not excessive boldness of the best big Conrad Johnson tube amps.
Despite all of this, they are very very engaging and when the music and sources are right just as compelling to listen to as the best amplifiers I have heard.
Unlike the worst SS amps, they also don’t sound thin, compressed, underpowered or grainy at all. I just listened to Trombone Shorty’s latest tracks via Jazz FM 91 and man, freaking awesome playback. Absolutely nothing was missing nor called attention to itself in terms of the amplifier.
Best,
E
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I will say, for the form factor, the Mytek is really small, even for a digital amp. I'm VERY curious to know what is inside it. :) A scaled down nCore? Pair of Pascal amps???? Hmmmm......my screwdrivers scream to be let loose to see inside. :)
I'm such a fanboy Mytek should send me a prototoype. :)
Best,
E
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George,
It is an open forum. That gives me the right to every single word in my last post.
Cheers,
Erik |
@ebm
I really appreciate your careful reading of the purpose of this thread, not to mention your thoughtful and nuanced contribution to the hobby in general.
I can only hope that the you can contribute as much for others in your life.
Best,
E
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@randy-11
I am a huge Mytek fan, Randy, how did you learn about the amp? I haven’t heard a peep about it.
Best,
E
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Greg,
Good to hear. TBH I've only heard B&W speakers with Krell amps, and that combination never made me reach for my wallet.
Interesting you find the ICEPower modules working so well for you. :)
Best,
E
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I should say that in the mid-80’s I did get to listen to early Class D amplifier from one of our vendors. It was not then up to snuff, especially not with metal dome compression drivers. :)
Best,
E
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Hy Roxy,
I never did. My experience in the pro world was in motion picture auditoriums. At the time my employer bought Hafler amplifier modules, attached their own supplies, and their own surround processing. We probably kept Hafler in business a lot longer than they would have been otherwise. I understand they have come back though.
My day job is esoteric related to IT.
My current set-up uses custom loudspeakers driven by ICEPower 250ASP modules. I did a lot of listening and comparing them to Parasound Halo A23 amplifiers, which while small, are fabulous performers. I rate the two as equivalent in sound quality.
Best,
E
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