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RE: AVI - Class D development

chebby wrote:

Diamond Joe wrote:

Do class D amps consume less power than more traditional designs?

Yes.

 

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.

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RE: AVI - Class D development

John Duncan wrote:

I don't think I've ever heard a class D amp, unless my Yamaha receiver had them.

You probably have one in your mobile phone John

regards

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RE: AVI - Class D development

fr0g wrote:

chebby wrote:

Diamond Joe wrote:

Do class D amps consume less power than more traditional designs?

Yes.

 

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.

Good, thought so, cheers chaps, could be the way forward for me... maybe
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RE: AVI - Class D development

drummerman wrote:

John Duncan wrote:

I don't think I've ever heard a class D amp, unless my Yamaha receiver had them.

You probably have one in your mobile phone John

regards

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.

Hi-Fi - Yamaha RX-V667 > AVI DM5 > AVI subwoofer

Head-Fi - Epiphany Acoustics EHP-O2Di > Sennheisser HD700

Portable - Sony NWZ-A847 > Westone UM3x

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RE: AVI - Class D development

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?

 

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RE: AVI - Class D development

JonFountain wrote:

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?

 

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.

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RE: AVI - Class D development

http://en.wikipedia.org/wiki/Class-D_amplifier

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RE: AVI - Class D development

busb wrote:

JonFountain wrote:

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?

 

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.

 

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

 

 

 

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RE: AVI - Class D development

John Duncan wrote:

I don't think I've ever heard a class D amp, unless my Yamaha receiver had them.

 

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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RE: AVI - Class D development

JMacMan wrote:

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.

this is totally incorrect. the only reason why class D measures well is because they use high levels of negative feedback. therefore such amps have very low output impedance, as a bonus. however, you'll never get an open loop class D amp that will measure well. even a SET next to such an amp will be a benchmark impossible to beat.

JMacMan wrote:

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.

yeah. I'd like to see how the measurements change at 0.5W or into high frequencies. it's well known truth that amps that solely rely on loop negative feedback to get decent standard THD measurement (at 1kHz) don't measure quite well at low power levels  and into high frequencies (if the open loop gain is very narrow).

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RE: AVI - Class D development
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RE: AVI - Class D development

Interesting link, thanks dm. 

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RE: AVI - Class D development

Well, the Devialet D-premier is probably the best amp I've ever heard, and that incorporates a large slug of Class D, so I need no persuading it can be amazing.  

http://www.devialet.com/technology.php

I also like what I've heard from Primare, though it has not found universal favour in WHF.    I'm pretty sure it represents the future.  

Don't know what is in a cell phone, but can well imagine some car audio is Class D and I suspect our old Sony DAV-S550 cinema system was Class D (though Sony called it s-master or some such!) because it is tiny and cool to touch.  

Whether AVI can deliver on the potential I don't know.

Krell CD and amp, Michell/Rega/Grado record player, Hitachi and Sony tuners, Nakamichi cassette, SBT streamer, Sonus faber spkrs.  Sony and Samsung BDP & TVs. Qobuz > iPad > AudioPro Allroom Air One

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RE: AVI - Class D development

oldric_naubhoff wrote:

JMacMan wrote:

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.

this is totally incorrect. the only reason why class D measures well is because they use high levels of negative feedback. therefore such amps have very low output impedance, as a bonus. however, you'll never get an open loop class D amp that will measure well. even a SET next to such an amp will be a benchmark impossible to beat.

JMacMan wrote:

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.

yeah. I'd like to see how the measurements change at 0.5W or into high frequencies. it's well known truth that amps that solely rely on loop negative feedback to get decent standard THD measurement (at 1kHz) don't measure quite well at low power levels  and into high frequencies (if the open loop gain is very narrow).

Normally large amounts of neg feedback would be frowned apon but that feedback is applied to the modulated signal rather than the in-band output directly. As for measuring THD at 1kHz, the only thing that's going to reveal is whether a broken amp has been successfully repaired or not rather than equating THD with SQ. As for HF distortion, as long as those out-of-band products don't mix down into the audio spectrum, they are surely insignificant? THD will always rise when measured at low levels due to noise contributions overtaking harmonic content in amplitude.

What I can't understand is why anyone would go to the trouble of either designing or using off-the-shelf class D modules powered from an inefficient linear PSU rather than using switch mode technology. Both class D & switch mode supplies have far more to go wrong due to their innate complexity - that's my issue with such technology: reliability.

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RE: AVI - Class D development

oldric_naubhoff wrote:

JMacMan wrote:

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.

this is totally incorrect. the only reason why class D measures well is because they use high levels of negative feedback. therefore such amps have very low output impedance, as a bonus. however, you'll never get an open loop class D amp that will measure well. even a SET next to such an amp will be a benchmark impossible to beat.

JMacMan wrote:

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.

yeah. I'd like to see how the measurements change at 0.5W or into high frequencies. it's well known truth that amps that solely rely on loop negative feedback to get decent standard THD measurement (at 1kHz) don't measure quite well at low power levels  and into high frequencies (if the open loop gain is very narrow).

 

Being more specific, I can only speak on technical grounds of the TA-DA9000ES Sony S-Master Pro amp, which I own.  Sony state that it does not use any negative feedback - hence my stating it as such.

 

Quote:

"Superb open-loop performance. Traditional amplifiers typically generate substantial distortion in "open-loop" mode. That's why analog amps use Negative Feedback (NFB). Unfortunately, NFB exposes the signal to Transient Intermodulation Distortion and other dynamic problems. In contrast, the Sony S-Master Pro amplifier achieves excellent fidelity without any negative feedback at all! Distortion remains low without any sacrifice in transient and dynamic characteristics. Music comes alive."

 Here is a link to the full Sony White paper on the design.

http://www.docs.sony.com/release/ES_STR_05_Final.pdf


JMac

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