AVI - Class D development
- Thread starter drummerman
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News over at AVI; They are working on a class D amplifier module. This may be used to power a sub though the potential is probably there for other applications. According to the designer, Martin, Class D amplification, as available elsewhere has inherent problems such as 'if one thing goes, the whole thing goes'. It would probably be worth pointing out that others, such as Primare to name only one, use Class D without many reported problems but I guess it can only be good if someone like AVI research and develop the technology and implement their own solution. - In the same article a new, smaller active 2 way is speculated on. It could potentially bring active AVI ownership down to a new lower level.
regards
regards
Frank Harvey
Well-known member
I've liked Class D for quite a while now (and have made that clear on these forums), and I've yet to understand why those that promote 'accuracy' haven't embraced it. I've now used Class D amplification for my AV system for almost 4 years now and doubt I'll be going back to Class A/B.
FrankHarveyHiFi said:
Agreed.
I have an ES Sony TA-DA9000ES - Class D, but digital Class D, not analogue Class D, and more akin to an Lyngdorf or TacT Millenium in it's modus operandi than anything else.
I sold my Naim electronics after A/B'ing it to the Naim kit extensively, and would not swap it out for the likes of Krell, Audio Research, Mark Levinson, Gryphon or McIntosh which I've also comprehensively auditioned. In fact, in the context of a passive separates system, I've not heard anything else that I've liked better, and am a big fan of the Rotel Class D units also.
If you want lots of headroom/power reserves and superb sound quality in a multi-channel amp without the drawbacks of component life shortening excessive heat eminating from a compact box, to say nothing of the need for A/C in hot climates, Class D is very much the way to go IMHO.
JMac
John Duncan
Well-known member
chebby
Well-known member
John Duncan
Well-known member
JMacMan said:John Duncan said:
Something tells me that I've heard that one before,
JMac
I did copy and paste it...
JMacMan said:
As far as I see, Class D, as used elsewhere, usually offer relatively little dynamic headroom but almost double their power into lower loads. I am not so sure how this would sit with AVI's view of the importance of voltage swing and the dynamic potential of their more conventional power supplies. Perhaps, if these modules are powerful enough, 'headroom' is less important. That is if these will be used to power midwoofers/tweeters in the future, perhaps for the ADM's and perhaps a cheaper model. I guess that remains to be seen but they usually do things with purpose.
Regardless, it is good to see they dont rest on their laurels and continuously are evolving.
regards
From what I've heard, AVI were having some difficulty finding a class D design that fulfilled their requirements, so Martin is currently evaluating his own design.
Here is the rest of the info in a message from Ashley,
I'm being quoted on a other forum, so had better explain again precisely what we're doing.
As I previously said, Class D has higher distortion than good AB, which means, as JB discovered, it sounds better than Naim and as we know, it's not quite as good as our AB.
However Class D distortion at lower frequencies is good enough and for very high power applications, it is less expensive, so we're experimenting with a 500 Watt module for a possible new and better Sub.
The other application we're considering for our Class D amp is a very compact 5" Two way, where it would cost more than AB, but save space and avoid the need for cooling fins. It would only be used on the Bass driver and only then if it sounds okay up to 2-3kHz.
As I've previously explained, Class D is more expensive, more complex and so more likely to fail. Therefore we're thoroughly investigating every aspect of this by testing ours to destruction in a number of different ways. This will show us how to make it as reliable as our present range. So many PCBs were trashed over Xmas that we're waiting for more!
It may well be that we still decide not use Class D, but only by designing our own and not making all the mistakes DIY forum members do will we know. - Ashley James, AVI.
JC
Here is the rest of the info in a message from Ashley,
I'm being quoted on a other forum, so had better explain again precisely what we're doing.
As I previously said, Class D has higher distortion than good AB, which means, as JB discovered, it sounds better than Naim and as we know, it's not quite as good as our AB.
However Class D distortion at lower frequencies is good enough and for very high power applications, it is less expensive, so we're experimenting with a 500 Watt module for a possible new and better Sub.
The other application we're considering for our Class D amp is a very compact 5" Two way, where it would cost more than AB, but save space and avoid the need for cooling fins. It would only be used on the Bass driver and only then if it sounds okay up to 2-3kHz.
As I've previously explained, Class D is more expensive, more complex and so more likely to fail. Therefore we're thoroughly investigating every aspect of this by testing ours to destruction in a number of different ways. This will show us how to make it as reliable as our present range. So many PCBs were trashed over Xmas that we're waiting for more!
It may well be that we still decide not use Class D, but only by designing our own and not making all the mistakes DIY forum members do will we know. - Ashley James, AVI.
JC
I wish whfsv would review a Wyred4sound class d product. 500 wpc must be worth a review, surely?
My old Lyngdorf SDAI2175 was bulletprroof. Ran cold. 200 WPC into 8 ohms, almost double into 4 and drove my Dali Ikon 6s until they would burst. Sold on now, but it was a lovely piece of kit. I'd say class D was the way to go.
Although I did have a bit of a smelly, burny moment when I wired in my old sub through the High level without reading the small print.
Although I did have a bit of a smelly, burny moment when I wired in my old sub through the High level without reading the small print.
John Duncan
Well-known member
Diamond Joe
Well-known member
Do class D amps consume less power than more traditional designs?
Have to confess I always have one eye on the leccy meter.
Have to confess I always have one eye on the leccy meter.
chebby
Well-known member
chebby said:
Without researching (Google), I guess that's a given seeing as they don't act as a room heater. Mine was barely warm when pumping out ear-splitting levels of sound.
Diamond Joe
Well-known member
steve_1979
Well-known member
drummerman said:
I believe that class D is quite common in phones and MP3 players because it's more energy efficient which helps to extend the battery life.
I'm glad to see this topic come up as for the last few days I've been struggling to understand something about Class D and hopefully someone here can set me straight.
In the specification for my Myryad Mi it describes the amplifier secrion as being Class D and further that inputs are sampled at 48 khz to then drive the speakers with a 384 khz PWM signal. Now if I understand that correctly the 'sampling' is not to be confused with analog to digital conversion. However what really still stumps me is whether that 48khz rate nonetheless means that I'm wasting my time using high definition flacs on my Pioneer N50? In fact are Class D amps in general an anethma for high definition music?
In the specification for my Myryad Mi it describes the amplifier secrion as being Class D and further that inputs are sampled at 48 khz to then drive the speakers with a 384 khz PWM signal. Now if I understand that correctly the 'sampling' is not to be confused with analog to digital conversion. However what really still stumps me is whether that 48khz rate nonetheless means that I'm wasting my time using high definition flacs on my Pioneer N50? In fact are Class D amps in general an anethma for high definition music?
busb
Well-known member
JonFountain said:
Most class D designs are effectively analogue. I'm not sure if anyone has designed a digital version yet that works well. However, 384 divided by 48 equals a whole number of 8. I've read folk complaint that they don't like the idea of their music being chopped up by an HF frequency which makes sense if listening to vinyl but little sense with digital media that's already been sampled!
My Primare class D gives stunning levels of detail & imaging but I'd be frankly amazed if everyone liked the sound - it does not round off rough edges of bad recordings so can sound a little sharp at times. Given good recordings, it sounds amazing. Some prefer a more even rendition of their music collection than my system gives but that's personal choice.
I'd speculate that class D will take over from class AB. Whether class A will be legislated out of existence is no more likely than 3l engines for cars having the same fate. As has been pointed out most phones will be class D with switch-mode PSUs. Primare state that their class D's switch mode supplies conduct little noise back into the mains.
busb said:
Probably the best known analogue implementation of Class D is B&O ICE power - proprietary to them, but also often used under licence in other brands, such as Pioneer, Rotel, Jeff Rowland, and B&W amongst others.
The so called digital Class D, where the pulse wave for the output stages is generated directly from the PCM or PWM code inputted from the likes of an SPDIF connector is common as the linked Wikepedia article states, in home theatre in a box systems, but much rarer in so called high end product circles.
Exceptions would be the TacT, Lyngdorf and Sony S-Master Pro series, and as the wikepedia article states, these are less appealing from a design POV due to the inability to effectively implement global feedback schemes to lower distortion; instead each part of the audio chain needs to be corrected individiually/locally via DSP; there is also the problem of the amplfiers high output impedance due inablitiy to implement global feedback.
in the case of the Sony S-Master Pro designs, they use a design variant, where the pulse wave is generated from DSD - the amplifier was designed as a statement product, and for M/C SACD; a connected SACD player, via iLink, passes an DSD bitstream from player through the amplifier preamp DSP stages and power output stages, being converted to analogue just before the speaker terminals.
From a sound quality POV, it's the most transparent and ultra high resolution stand alone separates system amp I've ever heard, or had the privilege to own.
It has a massive linear power supply, but nonetheless can deliver a tested 170 watts per channel x 7 channels, all channels driven into 8ohms at < 0.01% distortion, so is no slouch on the measurments side of things, and does it all whilst remaining exceptionally cool running - no mean feat.
To my mind, Class D is the way of the future in terms of getting high performance, low distortion amplfiiers that will give off very little heat and with low power consumption and also fit into small spaces - hence well suited to active speakers, and also as a design considers the environmental concerns in the 21st century re power consumption/green impact etc.
JMac
John Duncan said:
John, if it helps or is of interest, your colleague Andrew Everard did a review of the Sony S-Master Pro TA-DA9000ES Class D amp in an edition of Gramophone some years back - he seemed quite positive about the technology; certainly I've found nothing to replace/better the TA-DA9000ES I own on overall sonic terms, with respect to stand alone separates amplfiers, which is also another reason I've jumped to active operation re my B&O Lab 9 purchase - I felt I'd gone as far up the separates tree as regards amplification quality, as I needed or wanted to go.
Bear in mind my TA-DA9000ES supplanted my Naim electronics (all bought new) and I did read on some US forums of audiophiles changing out some heavy hitting US amps such as McIntosh etc to go with the big Sony; I've extensively heard Krell, Audio Reseach, McIntosh as regards US amps, and Naim as regards UK amps, and wouldn't change out the big Class D Sony on sonic grounds for any of them - it's simply better when assessed as a musical reference to my ears - i.e. the closest approach to the original sound.
It's unfortunately now discontinued - an update exists - the TA-DA91000ES - but Japan only.
Sony are not exactly audiophile territory, but a look around the web, and what is available in Japan and the Far East reveals some pretty exotic stuff to say the least. It's a great pity the quality of their high end products and their technical design ability is not widely appreciated outside of their local geographic area.
HTH
John
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