The Good The Bad and The Ugly of Class D

MrC.

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Feb 16, 2019
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In the early days of class d I bought a 450w amp to biamp my speakers with a tube top end and a cube dsp to contour for my room nodes and to integrate with my 120w tube amp. As it happened, the addition of 450w of class d power degraded the sound and couldn’t compete with the impact or sound quality of 120 tube watts shared output and the class d went to the beach house to do duty there. Since that time I have heard numerous class d amps of varying cost and quality but found characteristics that repeated, particularly in the upper midrange and high frequencies which seemed exaggerated or “hard” whereas the lower mid and bass seemed to lack force or decay. This experience is years old and I have not heard the newest crop of gallium transistor based amps, except through YouTube videos. I wonder what the design issues are with these amps. The high amount of feedback used to make them work seems to sterilize the sound of those high feedback class a amps I have heard and therefore may do the same in class d. The promise of a cool running amp that delivers great sound is still enticing but I have not yet heard anything that I would replace my tube amps with. What is your experience and for designers, what keeps class d from competing with good class a?
 
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Hear Here

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Feb 14, 2020
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Portsmouth, UK
My first Class D was a DIY Tripath module that promised to offer all I needed in a power amp at the time - a few watts for a low price. Then I bought a Red Wine Signature 30 battery-powered amplifier that was receiving rave reviews at the time. Sadly it didn't perform well with my Avantarde Uno speakers, even after returning to Red Wine in the US for circuit mod to better suit the speakers. I sold it and moved to SETs (845 and PX-25 based) for the following 15 years or so. Then a couple of years ago I decided to move to SS and bought or home tested a dozen amps that I thought should offer good sound for the speakers - Class, A, AB and D. In the end I chose a Class D amp that overall offered best value.

As you say, Class D has advanced in leaps and bounds to the extent that I wonder why anyone should still be using amps that require the use of AC to maintain reasonable room temperatures. I've recently moved to the latest and greatest Class D module - Purifi Eigentakt. Even better will come in the future, but for now I have no desire to return to SETs or any ss technology. Class D has come of age and is with us, whether we think we don't like it or not. It's brilliant and not costly.
 
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DasguteOhr

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Sep 26, 2013
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First Tripath sounds harsh unorganic no matter if battery or power supply..crap. Then generate Bang& Olufsen her fabelous ICE Modules other Brands use in their Amps Burmester, Jeff Rowland etc.
They sound really good, music not hifi.
I forget the good sounding Ncore amps
 
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Hear Here

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Feb 14, 2020
734
432
155
Portsmouth, UK
First Tripath sounds harsh unorganic no matter if battery or power supply..crap. Then generate Bang& Olufsen her fabelous ICE Modules other Brands use in their Amps Burmester, Jeff Rowland etc.
They sound really good, music not hifi.
I forget the good sounding Ncore amps
If you like the Ncore and ICE modules, wait till you hear the Purifi Eigentakt. Much like DACs 20 year ago, Class D has developed rapidly and even now new technology is replacing older technology year by year. There are a few basic amps that feature Purifi, but I went for the NAD M33 and am more than happy with it, teamed with Avantgarde Duo XD speakers. NAD worked with Purifi to optimise the technolofy for their own amps and build under licence.
 

DasguteOhr

Well-Known Member
Sep 26, 2013
2,352
2,510
645
Germany
If you like the Ncore and ICE modules, wait till you hear the Purifi Eigentakt. Much like DACs 20 year ago, Class D has developed rapidly and even now new technology is replacing older technology year by year. There are a few basic amps that feature Purifi, but I went for the NAD M33 and am more than happy with it, teamed with Avantgarde Duo XD speakers. NAD worked with Purifi to optimise the technolofy for their own amps and build under licence.
i see some measurements of this amps really good;) ,thanks for the tipp
 
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sbo6

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May 18, 2014
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As of recent, there are some stellar Class D amps. Merrill Audio comes to mind as one I've never heard sound thin or unbalanced. Their newer high end models, the Element series which does use gallium nitride transistors and no feedback is supposed to be stellar. Also, I'm curious why you are jumping to Class D where there are many Class A/B SS amps that are also fantastic?
 

Hear Here

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Feb 14, 2020
734
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Portsmouth, UK
As of recent, there are some stellar Class D amps. Merrill Audio comes to mind as one I've never heard sound thin or unbalanced. Their newer high end models, the Element series which does use gallium nitride transistors and no feedback is supposed to be stellar. Also, I'm curious why you are jumping to Class D where there are many Class A/B SS amps that are also fantastic?
I think the main advantages of Class D are price for given performance and efficiency in the way they don't need a nuclear power station to keep them running and air conditioning to keep the house from overheating!

I didn't choose my Class D amp because of the latter but it does prejudice me against tubes and Class A, although I'd used these over much of the last 15 years. Now I have my Class D amplifier, I listen to far more music than ever before and I'm inclined to put my TV sound through my hi-fi if there's a music-based programme to watch. This used to be a once a year event - Last Night of the Proms, but I now regularly have the TV sound hugely improved by Class D and huge speakers.

The main reason though was that this amp matched or bettered the dozen other amps I home tested (Classes A, AB and D) over a 2 year period after deciding to move away from valves. Class D has come of age such that as good or better sound can be heard at a fraction the cost, both to purchase and to run, compared with the alternative technologies.

Gallium Nitride is certainly looking like the future but I'm not prepared to be a guinea pig and buy at huge cost an early example of this technology. Better to wait 2 or 3 years when the price is more sensible and the "prototype" phase is over. Another Gallium Nitride MOSFET amp at a fraction the cost of Merrill is the delightful little AGD Audion monoblocs.
 
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Kcin

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Mar 27, 2016
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I chose to build one of the Purifi EVAL boards into an amp. I am bi-amping and using the Purifi on the bottom. In many opportunities to evaluate it over the past several months, the Purifi is a solid contender. I have SETs, OTLs and PP tubes as references.

You can buy completed configurations now from VTV and other vendors. I built mine from individual modules and put it all together with some modifications - particularly around the binding posts and feedback circuit at this point.

In Soundstage , online review, they compare the Purifi EVAL to a Constellation amp with interesting results into Magico speakers.

 

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MrC.

Well-Known Member
Feb 16, 2019
47
45
83
I think the main advantages of Class D are price for given performance and efficiency in the way they don't need a nuclear power station to keep them running and air conditioning to keep the house from overheating!

I didn't choose my Class D amp because of the latter but it does prejudice me against tubes and Class A, although I'd used these over much of the last 15 years. Now I have my Class D amplifier, I listen to far more music than ever before and I'm inclined to put my TV sound through my hi-fi if there's a music-based programme to watch. This used to be a once a year event - Last Night of the Proms, but I now regularly have the TV sound hugely improved by Class D and huge speakers.

The main reason though was that this amp matched or bettered the dozen other amps I home tested (Classes A, AB and D) over a 2 year period after deciding to move away from valves. Class D has come of age such that as good or better sound can be heard at a fraction the cost, both to purchase and to run, compared with the alternative technologies.

Gallium Nitride is certainly looking like the future but I'm not prepared to be a guinea pig and buy at huge cost an early example of this technology. Better to wait 2 or 3 years when the price is more sensible and the "prototype" phase is over. Another Gallium Nitride MOSFET amp at a fraction the cost of Merrill is the delightful little AGD Audion monoblocs.
How interesting that you decided to move away from SET sound to class d. I like SET sound best for high efficiency speakers but my main speakers are Inefficient. The amount of heat put out by a 120w otl amp is very high so the idea of good sounding class D is attractive to me. I was under the impression that the efficiency of the Avante Gardes would allow you to play them with a stereo 2a3 amp. How do you find the sound of vocals or spoken word with your NAD amp?
 

Hear Here

Well-Known Member
Feb 14, 2020
734
432
155
Portsmouth, UK
How interesting that you decided to move away from SET sound to class d. I like SET sound best for high efficiency speakers but my main speakers are Inefficient. The amount of heat put out by a 120w otl amp is very high so the idea of good sounding class D is attractive to me. I was under the impression that the efficiency of the Avante Gardes would allow you to play them with a stereo 2a3 amp. How do you find the sound of vocals or spoken word with your NAD amp?
Hi Mr C from another Mr C.

After using and enjoying SETs for many years, it dawned on me that I'd only turned on my hi-fi when I wanted to listen to music. It was never on to provide background music when I'm working at home and I never enhanced my TV sound by putting it through the hi-fi. The subconscious reason was that valves have a limited life, they are costly to replace and the energy used by having them on most of the day is unjustifiable in the 21st century.

I decided that I'd look for an SS alternative and go that route if I could find one that sounded as good as the SETs I'd previously used - 845 and PX-25 based although I'd also had one using 300B and anther OTL using 6C33C. I home tested a dozen amps of Class A, AB and D but eventually chose the NAD M32 (subsequently changed for the even better M33) as it offers very good sound quality and is very reasonably priced. I certainly didn't go looking for Class D, but the NAD won out over the A and AB contenders as the technology has improved dramatically since the days of Tripath, etc. As an all-in-one, there are no costly cables involved - I hate cables and the cable that improves sound has not yet and never will be invented. I’m very happy with the M33 despite it being far more powerful than I need with my 107 dB speakers. I may add an alternative amp that offers a different music presentation so I can choose when listening critically and this may be a tube amp, but it won’t be for everyday use.
 

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