Class D amp performance

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raddar

Class D amp performance
« on: 22 Nov 2017, 03:34 pm »
As I await my new class D Icepower amp, I found this comment on the Harbeth forum last month interesting, Is it still valid regarding Class D amps in 2017?


I would just like to caution you about abandoning 50 years of proven solid state Class A-B amplifiers. I had a flirtation with a home made Class D amplifier a few years ago, and my initial impression was very positive. However ...... after extended listening a sense of fatigue was inescapable. Technology has improved, but I'm unlikely to have the curiosity to revist that again. The Hegel (or equivalent) amps we use at Bristol are better than they need to be, and more than good enough for us at HQ. The subject of power amplifiers is closed for the rest of my life.

DIY test for the amplifier detective.

Arm yourself with a cheap as chips AM radio. Bring it near the speaker cable from amplifier to speaker and listen. Do modern Class D amps still radiate RF hash mixed with the audio on the speaker cables, swamping AM radio stations? Try it and ask yourself if you feel comfortable with the notion that your swanky digital power amplifier is, in essence, a broadcasting radio transmitter posing as an audio amplifier.

Strange how you don't read simple, practical tips on the guru forums.
Alan A. Shaw
Designer, owner
Harbeth Audio UK


zoom25

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Re: Class D amp performance
« Reply #1 on: 22 Nov 2017, 04:43 pm »
I did this a few weeks back with an AM radio. The iMac and the switching power supply adapters were the worst. You could hear the response change on the AM radio as the load on the stock power supplies changed. Same went for the 27" iMac when I played around with the brightness.

For my Class D Amphion Amp100, I didn't check the speaker cables directly as they are behind the iMac and hard to get to. Although, I did take the AM radio near the amp itself. There is still interference radiated, however, much less than the iMac or the switching power adapters. You can even hear some of these adapters buzz for a second or two after they've been unplugged.

I've switched over to shielded or double shielded for most of my cabling: power, ethernet, USB, AES and balanced interconnects.

zoom25

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Roninaudio

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Re: Class D amp performance
« Reply #3 on: 22 Nov 2017, 04:55 pm »
I think this quote sums it up:
"Folks, this is the future. We have heard vast improvements of Class D amplifiers during the last 10 years, and we are at or near the point where the technology is largely irrelevant to the final sound. The sound of audio components is more dependent on the implementation than on the underlying technology."

To the implementation point, my amps use:
"The Analog Cell features Class A operation of MOSFET devices and is designed specifically for this application to work well with the latest ICEPower 300ASC amplifier modules"

My only other experience with Class D was with Peachtree. That was short lived as the amp blew up and had to be returned. I think the technology has evolved to the point that we all have many options for "Hi-Fi" and Class D is certainly one of them in 2017 and beyond.  As per the AM radio exercise, I am not sure of the relevance. The fact that noise exists around electronics is no surprise. My 2c anyway....

FullRangeMan

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Re: Class D amp performance
« Reply #4 on: 22 Nov 2017, 05:05 pm »
Reactors from leds and fluorecent lamps also emit a strong UV field.

Photon46

Re: Class D amp performance
« Reply #5 on: 22 Nov 2017, 05:27 pm »
First thing I'd say is that opinions about class D are so varied that the responses one gets are nearly meaningless as applied to one's own tastes and ears. The quoted source you use as a reference opinion is laughably naive in the sense that he use one exposure to an inexpensive class D amp as his baseline for a judgement abut the whole genre of class D. Second thing I'd say is that a valid opinion in one system can be completely reversed in a different system. Case in point, I was a very early purchaser of the first PS Audio HCA-2. Reviewers were very positive about this amp and then slowly the consensus seemed to change as people heard deficiencies in certain areas. I heard those same things myself and went through two rather expensive upgrade/modifications done by Reference Audio Mods. It was a much better amp but still didn't achieve what I was looking for with the speakers I was using at the time, Magnepan 1.6's and ACI Talisman SE's. I put the HCA-2 away in the closet for many years. I recently pulled it out of the closet  just for the heck of it to try in my current set up with a Dehavilland Ultraverve III preamp and Tidal Piano Cera speakers. My first impression was: Is this the same amp I remember, it sounds WAY better than I recall! Then I tried powering it through my Audience power conditioner, another not so subtle improvement. It has a particular sound that isn't going to appeal to someone who wants a mellow sounding amp and it does have a noise floor that's no match for the quietest amps, but it works astonishingly well in the context of my current system. (I really look forward to hearing how the newest Icepower AS1200 amp from Mike at Mivera is going to sound.) No single opinion about any audio product or technology is valid in every context, we have to learn to listen for ourselves. Ears that love single driver horn loaded speakers powered by flea watt amps probably won't like what I like and vice/versa, that's fine and wonderful. Obviously the rapidly expanding range of amplification products that use class D technology means that large numbers of listeners like what they hear.

raddar

Re: Class D amp performance
« Reply #6 on: 22 Nov 2017, 06:55 pm »
Thanks for your input guys :D

FullRangeMan

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Re: Class D amp performance
« Reply #7 on: 22 Nov 2017, 08:43 pm »
https://www.youtube.com/watch?v=ofN1EsZVoGY
The LED TV test is even more impressive, too powerful field.

Mr Peabody

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Re: Class D amp performance
« Reply #8 on: 23 Nov 2017, 04:17 am »
I think Class D as an amp design gets some of the bad rap from guys buying cheap amps.  Sometimes you get what you pay for.

I know Class D can be good, I've heard some I'd keep by the likes of Audio Alchemy, Cyrus and Merrill Audio to mention a couple.  It also must be growing and selling as most name brand manufacturer has a Class D line or model, ARC has done it for some time, NAD, Rotel, there's several others.  I don't think it will go away, only improve.  I have to mention Devaliet, probably my favorite.

I watched some of that YouTube video, I was thinking that EMI noise could be the beginning of a good song, LOL 

Armaegis

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Re: Class D amp performance
« Reply #9 on: 23 Nov 2017, 05:58 am »
I don't understand how people are still arguing over this.

You can get really good class D these days, but it doesn't necessarily come cheap or light anymore. But the thing is, it's super easy to get cheap and light class D, and sometimes I'm more than willing to sacrifice sound for those two qualities. Maybe I'm building a mobile battery device, maybe I'm very space or heat restricted, maybe I need to hit a certain product price point, or maybe I'm just a noob designer and that integrated chip package is my best way to start.

Can I get cheap and light class A? Well... not really, and if I do it'll be of severely restricted power output. There are plenty of crappy class A and A/B amps out there, but people like picking on D for some reason.

How old is that quote from Alan Shaw? Frankly I'm surprised anyone can take that at face value. He's evaluating an entire class of amplifier based on a single data point... a single home-made data point. You can't take that seriously. That's like me taking a bite out of a mackerel fresh from the lake and declaring that all sushi is bad.

Wind Chaser

Re: Class D amp performance
« Reply #10 on: 23 Nov 2017, 06:11 am »
Having come from tubes, including a few very nice SETs, I'm fully embracing Class D and completely in love with it.  :D :D :D :D :D :D :D :D :D :D :D :D :D 

No more tubes on my horizon.  :D :D :D :D :D :D :D :D :D :D :D :D :D 


JLM

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Re: Class D amp performance
« Reply #11 on: 23 Nov 2017, 12:14 pm »
Have been a solid state guy for nearly 50 years.  Have tried tubes a couple of times, but either they lacked tube palpability, or had tons of bass bloat, or there was way too much warm syrup coloration.

On my 2nd pair of class D mono-blocks (Temple Audio, see my review here at AC from June).  Way smaller, lighter, and cheaper than my 1st (70 vs 100 watts at 8 ohms), but more importantly the 10 years newer ones sound better:  reveal more detail and somewhat improved sound staging; noticeably more dynamic and increased/more solid bass; dynamics and transparency improved. 

So perhaps the naysayers need to listen to the latest offerings.

opnly bafld

Re: Class D amp performance
« Reply #12 on: 23 Nov 2017, 01:12 pm »
Have been a solid state guy for nearly 50 years.  Have tried tubes a couple of times, but either they lacked tube? palpability, or had tons of bass bloat, or there was way too much warm syrup coloration.

Is this your Alan Shaw imitation?  :duh: 

 :roll:



As already mentioned all types of amps can sound good or bad.

JLM

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Re: Class D amp performance
« Reply #13 on: 23 Nov 2017, 01:49 pm »
Is this your Alan Shaw imitation?  :duh: 

 :roll:



As already mentioned all types of amps can sound good or bad.

Are you referring to Alan Shaw from Harbeth?  I'd never heard of him, until I just googled him.  But I did own LS3/5a type of monitors in the 70/80's. 

opnly bafld

Re: Class D amp performance
« Reply #14 on: 23 Nov 2017, 01:59 pm »
Did you read the first post?

Mr Peabody

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Re: Class D amp performance
« Reply #15 on: 23 Nov 2017, 03:29 pm »
I only heard one Class D amp (the brand)  I think it was a 440 if memory serves, I put it in my system and it had way too much top end emphasis for my taste.  However, for the price the build and other aspects of the sound was good.  This was a couple years ago so hopefully the frequency balance is better now.

Roninaudio

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Re: Class D amp performance
« Reply #16 on: 23 Nov 2017, 04:03 pm »
I have these and in my humble opinion, the sound is great and they are keepers.  The only other amps I have heard that really impress me are Primaluna which is whole different discussion.  (and there are a million amps I have never heard).  These might be called "D" hybrids?  Not sure but paired with my Dynaudio, they sound killer...... Frequency balance is great but perhaps that is in the design/implementation of the Class A MOSFET based Analog Cell for the input stage?  Like mentioned above, there are probably good and bad examples out there of every conceivable technology possible - Carver "Cube" anyone?

http://www.psaudio.com/stellar-m700-mono-amplifier/

Oh- have a Happy Thanksgiving everyone...... Off to get fat..lol




nickd

Re: Class D amp performance
« Reply #17 on: 23 Nov 2017, 05:40 pm »
I switched to digital amplification (Lyngdorf) mostly because of space requirements and heat generation. Here in So Cal today it is going to be in the 90’s. Power bills north of $500. Per month are also quite common.

There are things I still enjoy about really good class A and A/B amps. That said, the ease of operation and amazing sound of some new designs has created a new class of reference components. No class A or A/B amp I am aware of at any price can match the crazy low noise floor of my little, cool running TDAI 2170. Through in reference quality volume control, a built in state of the art DAC, room perfect DSP and digital crossovers.

Lots of fun indeed.