View Full Version : Class D come of age - Coherent amplification
Firebottle
24-01-2019, 09:33
As a techie I have sort of been following the evolution of 'digital' or class D amplifiers.
I know there are now some very good examples but I haven't heard any, until now.
During my recent visit to Coherent Systems I had the privilege of experiencing Tony's latest power amp, as yet unreleased.
It has some amazing specs (20nS rise time, 100A instantaneous current delivery) but what does it sound like?
The short answer is nothing. Zip. Nada.
By that I mean the music is just there in front of you. Loud or quiet, any genre just music.
Forget valve or solid state. Forget analogue or digital. Forget pixie dust or massive heatsinks - this amp is very efficient :D
This is the realisation of 'straight wire with gain', the rather wonderful line that Peter Walker came up with.
Fantastic doesn't cover it.
:cool:
walpurgis
24-01-2019, 09:40
I can believe that Alan.
I have my cheapo TPA3116 in the system as my main amp at the moment and can't fault it. The valves, Quads and Sugden etc are taking a holiday.
jandl100
24-01-2019, 09:46
Interesting.
I've heard a fair few class d amps and while there was a wide range of presentations and excellence they all had a characteristic smoothing over of the finer details.
I guess the Coherent amps have overcome this?
ianlenco
24-01-2019, 09:53
I've got a Rogue Audio Sphinx 2 which has a valve pre and class D (Hypex I think) power stage. Very happy with the sound and find it very funny when folk who have been listening quite happily to my system suddenly look as though someone in the room has farted when I tell them it's Class D!
Firebottle
24-01-2019, 10:32
Interesting.
I've heard a fair few class d amps and while there was a wide range of presentations and excellence they all had a characteristic smoothing over of the finer details.
I guess the Coherent amps have overcome this?
And some. Best sound I have ever heard.
Firebottle
24-01-2019, 10:34
... when folk who have been listening quite happily to my system suddenly look as though someone in the room has farted when I tell them it's Class D!
That's class Ian :lolsign:
hifinutt
24-01-2019, 11:38
wow , i had a pair of tony [ coherants ] ref 1000 modded amps and they were superb . much better than the previous ref 1000 . had many things off tony over the years and glad you could get down there . i miss his place in malvern and ripple
he has a renovated pair of belles mb200 which are beautiful amps . had some before the msb , be interesting to compare them to the fb hybrid monoblocks
hifinutt
24-01-2019, 11:40
myself and deggie were listening to a little topping on monday with some p3esr and it did not sound bad at all
23 watts and 55 quid s/h !!!
Alan brought with him his Firebottle mono's, which in fairness where very good, they drove the Quadral Galan's really well and sounded very good considering the cost, a real bargain imho.
Sherwood
24-01-2019, 11:54
I am convinced that class d is the way forward and that there are several current amps using this technology which can compete with the best in other classes. I speak as the owner of a very nice valve amp and beefy class a/b amp, as well as various "chip amps", class t designs and so forth.
As an additional consideration, and from an environmental perspective, I feel very guilty these days about the inefficiency of valve and class A designs, even though the SQ may be great.
Geoff
QUOTE=Firebottle;1053070]As a techie I have sort of been following the evolution of 'digital' or class D amplifiers.
I know there are now some very good examples but I haven't heard any, until now.
During my recent visit to Coherent Systems I had the privilege of experiencing Tony's latest power amp, as yet unreleased.
It has some amazing specs (20nS rise time, 100A instantaneous current delivery) but what does it sound like?
The short answer is nothing. Zip. Nada.
By that I mean the music is just there in front of you. Loud or quiet, any genre just music.
Forget valve or solid state. Forget analogue or digital. Forget pixie dust or massive heatsinks - this amp is very efficient :D
This is the realisation of 'straight wire with gain', the rather wonderful line that Peter Walker came up with.
Fantastic doesn't cover it.
:cool:[/QUOTE]
hifinutt
24-01-2019, 12:07
Alan brought with him his Firebottle mono's, which in fairness where very good, they drove the Quadral Galan's really well and sounded very good considering the cost, a real bargain imho.
thanks tony , yes they are very compact and easy to fit in . always good to try alternatives though
Firebottle
24-01-2019, 12:45
Phil is referring to my hybrid valve/mosfet monoblocks.
The amps I took down to Tony's place are a new compact class D monoblock https://theartofsound.net/forum/showthread.php?60744-Sneak-preview-New-Miniblocks
The rating is 28W into 8 ohm.
Bigman80
24-01-2019, 12:48
Phil is referring to my hybrid valve/mosfet monoblocks.
The amps I took down to Tony's place are a new compact class D monoblock https://theartofsound.net/forum/showthread.php?60744-Sneak-preview-New-Miniblocks
The rating is 28W into 8 ohm.Very good little things they are.
hifinutt
24-01-2019, 15:35
Phil is referring to my hybrid valve/mosfet monoblocks.
The amps I took down to Tony's place are a new compact class D monoblock https://theartofsound.net/forum/showthread.php?60744-Sneak-preview-New-Miniblocks
The rating is 28W into 8 ohm.
ah thanks for clarification alan
I was initially very sceptical about class D power amps, but not now, they seem to have it pretty well nailed and they will reach a stably unquestioned near perfection state soon.
I am using the active Icepower amps which are a part of my Betas, and this is easily the most revealing speaker I have had, with one slight reservation. the upper Heil, which does the upper range above 2.8kHz is very screechy on FM, more than with my own design and with an ATC SPA2.
Guess what, the amp in the pack driving this is a normal class AB amp.
The cat is unhappy because he used to bask in the ATC's heat, and the Icepower is 97% efficient so usually dissipating only one watt per side.
Over the years, I have investigated many switching designs, Tripath, Ice power, Hypex (Both UCD and Ncores) and the small Ice bricks, all have pro's and con's, some due to bandwidth issues, others due to average input stages and use of smps. There are some stand out designs, usually the lower power variety, which just seems to have some audio magic when you listen to them, like a high quality pair of stand mount speakers imho
As with all of these designs implementation is the key, these days with energy conservation firmly in mind, many power supplies have certain limitations which can impede the progress of quality amp design. With smarter power control, energy harvesting, smarter materials for FET's etc and storage having improved vastly over the last 10 years, scope has opened up to exploit certain aspects of switching designs.
One of the biggest gripes have been lack of real three dimensional staging with depth, tonal rendering and layering of instruments, power was never the issue or bass control (unless early ice power units) nor was the solidity of the sound. But delivering a convincing 3D soundscape with correct tonality, subtly and delicacy a million miles away.
Now I feel it is possible to have virtually all the fluidity of top draw valves like 2A3's / EL34's etc, but without any draw backs, top to bottom linearity, fifth harmonic + bandwidths, zero noise through the speakers and no indoor sauna's. Plus the ability to drive a much wider range of speakers thus giving freedom to chose a more closely matched speaker / amplifier impedance with recourse to speakers 95dB+ that you can hear the cabinet resonant a mile away! Joking aside, in the next five years you will see some quite delightful all digital designs that will sound very decent and put the Devialet / Paul Miller best amp in the world to bed once and for all :rolleyes:
Valve amps will always be here enthusiastic lovers of thermionic amplification will only stop loving them when they pass away :)
Interesting snippet, last year a not insignificant number of valve amp owning customers (of many years) decided to change to either quality a/b or some form of small powered PWM amp, still kept the valve amps but have not felt the need to put them back in their systems for what ever reason.
Its not going to start a revolution, so fear not :), it is just giving people,food for thought that even five years ago they would never have given a second thought.
Just as a side bar D'agostino has just launched a pair of mono-blocks (Relentless) which can chuck out 1.5Kw @ 8ohms, 6KWrms @2 ohms (at which point it is consuming 10KW of raw power :lol:) Deliver 400Amps (peak) weigh a bit more than me 258Kg each :stalks: and should heat the whole of Huddersfield quite easily, and measure not far off 1 meter deep :eek: and these are solid state!
Full rail P 2 P voltage is a staggering 320Vac, need to start a car with a flat battery? just point the amp terminals within 1/2 a mile and hey presto it would start a Juggernaut. Maybe its a secrete Trump EMP weapon on the QT. Cost? my guess the DarTZeel mono's are around the £140K a pair damn fine their are two, so I would suggest around the £200K mark.
Has the world gone bonkers, quite possibly but you can smile while clocking up the electric bill :lolsign:
sq225917
24-01-2019, 19:37
So which class d units do they use?
Firebottle
25-01-2019, 07:51
Tony's amps are bespoke. He is a very talented engineer.
Haselsh1
25-01-2019, 08:20
I've been wanting to try out a pair of Temple Audio monoblocks with additional PSU's for quite some time. Maybe one day I'll get the chance (and the £1k required). I'm borderline thinking that they may be better than my current power amp. Then again, they may not. My current system gives me what I want apart from lots of headroom.
sq225917
25-01-2019, 09:33
Tony, if you've designed a new Class D circuit for your amps that's not based on another OEM design then hats off to you mate, that's big job and a hard one to get right.
I'd be very interested to hear Tony's class d amp. I identify with what he's saying when comparing valve and class d. I find I cycle through a few power amps to give me a variation in the sound I experience. There are a few more amps in my stash than my signature suggests. The favourites however are the class d and the two valve amps. I select the class d for a few weeks when I'm craving a tighter, more "precise" sound, after those few weeks I then switch to valves to give me some extra meat to the soundstage and that fluidity Tony talks about. The valves being SE and PSE will be euphonic but they sound good and my speakers are a great match for them. Again...after a while a want to switch the presentation again so I revert to class d, sometimes via class a/b solidstate Philips Black Tulip or current dumping Quad 306.
If I could finally have all the positive attributes in a single amp it would be wonderful.
Hi Tony,
Interesting stuff, as is Alan's appraisal of the Class D amps in question. I have little experience of Class D, so can't really offer much input to the discussion. However, were Class D amps used in the system you demonstrated at Cranage Hall last year?
As you know, I spent some time in your room listening to music and chatting with you, so if that was Class D I may have some kind of handle on what it does, musically:)
Marco.
Are my now ten year old class D Icepower amps regarded as not very good then?
Dennis,
In answer to your question, if they are ICE power 1000ASP modules they have a limited bandwidth of 38Khz +/-3dB so not even the second harmonic is captured.
From personal experience with a wide range of amplifiers, a minimum BW of the four harmonic (80Khz) more is better but having over 1/4 mhz is a bit OTT is required to begin to truly recreate a proper three dimensional, textural layering imho.
The later ASX series are a big improvement over the ASP models which were really for pro audio big banger speakers and subs. Though the 500 ASP I always felt far more engaging even only if it had 500watts lol still swing 38 amps at peak, but it had a 80Khz bandwidth.
Everyone experience with these may well be different, however the bottom line is what each of us really holds close to their heart for perception of a quality sound.
The
Hi Tony,
Could you answer post #22 please, specifically whether it was Class D amps I was listening to in your room at Cranage? Churz!:cool:
Marco.
I cannot see the need for the bandwidth you quote Tony.
montesquieu
25-01-2019, 21:15
Dennis,
In answer to your question, if they are ICE power 1000ASP modules they have a limited bandwidth of 38Khz +/-3dB so not even the second harmonic is captured.
From personal experience with a wide range of amplifiers, a minimum BW of the four harmonic (80Khz) more is better but having over 1/4 mhz is a bit OTT is required to begin to truly recreate a proper three dimensional, textural layering imho.
The later ASX series are a big improvement over the ASP models which were really for pro audio big banger speakers and subs. Though the 500 ASP I always felt far more engaging even only if it had 500watts lol still swing 38 amps at peak, but it had a 80Khz bandwidth.
Everyone experience with these may well be different, however the bottom line is what each of us really holds close to their heart for perception of a quality sound.
The
In agreement with Geoff that Class D is undoubtedly the future, my concern has been that any I've heard have been close, but not quite up to the best valve amps in terms of musicality. (My view is that the best Class D amps have probably already exceeded what A or A/B solid state can manage). So still 'the future' then even if it's getting nearer.
Tony, can you give us a view on price? £140k amps of the kind you mentioned as competition aren't real world for people here, any more than they are likely to drive home in a Bugatti.
The biggest question really is 'what's the damage?' which for many will determine whether a listen is something urgent or a curiosity that can wait till some random hifi show.
sq225917
25-01-2019, 21:26
I cannot see the need for the bandwidth you quote Tony.
Maybe there's a benefit to having a faster modulator which has shorter clocking cycles and therefore greater precision, the converse of course is a greater requirement on the output filter to block all HF EMI reaching the speaker.
Tom, my experience of Class D amps says they haven't reached the best of class A/B yet. Back to back with perfectly built NC400's a I ended up going for the Class A/B unit. Of course there may be gains to be had from better input buufers and output filters for the NC400s
In agreement with Geoff that Class D is undoubtedly the future, my concern has been that any I've heard have been close, but not quite up to the best valve amps in terms of musicality. (My view is that the best Class D amps have probably already exceeded what A or A/B solid state can manage). So still 'the future' then even if it's getting nearer.
Tony, can you give us a view on price? £140k amps of the kind you mentioned as competition aren't real world for people here, any more than they are likely to drive home in a Bugatti.
The biggest question really is 'what's the damage?' which for many will determine whether a listen is something urgent or a curiosity that can wait till some random hifi show.Indeed many Hifi items have a higher than Hifi price tag. But plenty seem to afford them. They just generally don't frequent fora lol.
montesquieu
25-01-2019, 21:32
Indeed many Hifi items have a higher than Hifi price tag. But plenty seem to afford them. They just generally don't frequent fora lol.
Too busy running hedge funds, out shooting with Jackie Stewart or flying their own private jets I suppose.
Indeed many Hifi items have a higher than Hifi price tag. But plenty seem to afford them. They just generally don't frequent fora lol.
They do just not this one,usually.
montesquieu
25-01-2019, 22:29
They do just not this one,usually.
True actually. Some of the American fora are hilarious, the amount of willy-waving.
Having said that hifi willy waving is as nothing compared to watch fora.
Not sure if my monoblocks are class D or what they are tbh. Probably are. Good with some stuff they are, less so with others.
One thing that never fails to keep me on my guard about sagging stuff or for that matter praising it is you need to try things in various systems.
There it probably no right way.
But if I had the money I'd probably be going fir one if those valve jobs Tom and Ed have
I see a lot of confusion here
The DarTZeel mono's are class A/B I was citing them against the new D'agostino Relentless monoblocks again class A/B
Band width is very important if you come back with we only have 20Khz heating range then you may not understand harmonic reproduction in musical instruments and how recording studio's use microphones with far greater recording capabilities than 20Khz. How we precieve how sound is formed and we actually reassemble this information inside our cerebral cortex.
Simon completely agree with the Hypex even with a fully discrete front superior power supplies again only 50khz bandwidth again still a way off the mark.
Class A/B still very good but you have banks of FET's which need to be fully balanced and matched, short main supply pathways heat sinks etc.
Imho the switching frequency of the module and gate driver technology are among key elements that are required to help bring a quality sound from a switching amp.
Marco
The amplifier in room we used at Cranage was a TAD Implementation of a pwm switching amplifier their own technology again 5th harmonic bandwidth and a very good example
The main problem with solid state amps is the ability to recreate the trailing note decay and sustain completely this helps deliver true three dimensional soundscape imho it needs to have the speed not just to deliver the leading edge of the note but to fully form the decay without losing the next leading edge note by founding congested or pounderous a simplist assement but an important one whilst retaining top to bottom linearity.
This is not a valve amp knock not so long ago I was discussing amplifier design with a very well known and respected UK thermionic manufacturer I was running through my observations on high resolution reproduction with valves not been as good as I suspected valve amps could deliver, his response was thus 'what the do not hear they will not miss'
I own apair of highly respectected 211 monos and they sound wonderful on more realistic speakers for myself but boy the heat the room!
Listening to the new amps called Liquid Music will be quite easy in the not too distant future, anyone serious about auditioning any piece of equipment seriously will seeker a dealer that stocks said equipment have an audition at said dealer and if liked a home audition is then arranged simple as that
Waiting for show will not really give you a good indication of its real world performance as wrought out by the show report threads in various forums slagging off all bar a few select rooms that are favoured by individuals person preferences imho
So those really and genuinely interested in listening to a piece of eqipment will make the effort to listen to rather than a lot of tyre kicking hot air
Most high value systems in the uk are not owned by real music lovers, interestingly I know of two members on this forum who have six firgue systems yet are only interested in the music sections and do not partake in discussions regarding equipment as I suspect there are on other audio forums
You can put together a pair Ncore monos with the one psu forcaround £800 inc cases if you wish to try out what many consider a gratbexample of the breed
This design has been 12 years in the making so it has not been taken lightly there will be mono blocks in the not too distant future as well
Think that covers it chaps
montesquieu
25-01-2019, 22:46
Think that covers it chaps
You missed the price indication I was asking for ... hope they are not in the 'If you need to ask, you can't afford it' category ...!
Tom
Apologies they will not be in the W1 pricing category in fact when at market no more than a well respected solid state or valve amps that are readily available at most dealers
My experience of Class D is that the ‘signature’ colouration sound is entirely different to that of other amplification styles/modes and can therefore easily fool people into thinking it is fault free because it doesn’t exhibit any of the faults they are expecting (based on previous experience). However, this is not to say that it is actually fault free (bear in mind one of the amps I use is class D).
montesquieu
25-01-2019, 23:02
Tom
Apologies they will not be in the W1 pricing category in fact when at market no more than a well respected solid state or valve amps that are readily available at most dealers
Was a genuine question Tony though I do understand this may not be the place you want to answer it. PM incoming.
Has anyone considered the switching noise that Class D amps inject into the mains supply, and the subsequent effect on the performance of the partnering equipment, connected to the same supply?
As ever in audio, there is no 'magic bullet' - and that includes Class D amps;) Although no doubt Tony's is a good one!
Marco.
My experience of Class D is that the ‘signature’ colouration sound is entirely different to that of other amplification styles/modes and can therefore easily fool people into thinking it is fault free because it doesn’t exhibit any of the faults they are expecting (based on previous experience). However, this is not to say that it is actually fault free...
Yup, and leading on from what I've just written, and that *everything* in audio equates to some form of compromise, I completely agree with your point of view.
Marco.
I would agree a lot of the PWM's have a house sound, there are few that do not.
Switch frequency noise can play a large part of that issue, however most of these devices switch around 400-600Khz, and with SMPS the idea was to cancel out the switching of the amp/smps with each other.
Part of the benefits of the device I use is that you can move the switching frequency around by a large amount, which can help a great deal, is not the only issue that can be beneficial though.
Well, I dunno. I use two systems, one with AB amplification; the other with class D amplification. They both sound great. I've never noticed much 'signature' colouration with either, or 'switching noise' with the latter. Of course, it's entirely possible that my aged ears can't distinguish such subtle effects, and/or that I'm easily pleased.
anthonyTD
28-01-2019, 17:29
I have some experience of Class D amps, [going back as far as 10 years or more] some were good, with respect to musicality, and some not so good, I also agree that some of the best sounding were/are low power versions, when you compare the technology involved in three of the main topologies, I would say that Class D when done well is the closest to the best valve amps out there, they both have something in common which I feel is key, that is; they both have a measureable output impedance, valves amps having an output transformer on its output, Class D having the choke/ filter network at the end, this in turn allows the output to vary somewhat inline with the speaker's change in impedance with frequency, which all conventional cone speakers suffer from.
If you compare this to the way conventional transistor amps work, ie; they have a very low [almost immeasurable] output impedance, this is very good when the nominal speaker impedance decreases, hence the amp will put more power into the speaker load, However; as the speaker impedance rises, well,,, its a different story.
Anyway, just my ramblings.
If Tony has managed to overcome some of the failings that were a real hurdle in original class D technology, then I say great! :)
Imho the switching frequency of the module and gate driver technology are among key elements that are required to help bring a quality sound from a switching amp.
Interesting, Tony, especially given what I've just written. However, does it address the noise inherently injected (specifically its detrimental effects on the SQ of equipment sharing the same mains supply) by that type of amplifier topology?:eek:;)
Seriously, though...
In that respect, it would be interesting to see what would happen if you set up two systems in your demo room, both sharing the same mains supply: one using one of your Class D amps, and another using something else that doesn't switch (perhaps a good valve amp), and whilst listening to the latter, see whether the effect of switching off the Class D [taking it out of circuit] had any effect on SQ?
Any mains conditioning you were using would, of course, also need removing before the test took place.
Or maybe, since you have access to measuring equipment, and know what you're doing, measure the effect on the waveform of the mains supply when the Class D amp is connected and switching, compared with one that doesn't switch, and observe the differences?
Those are the sorts of tests I would need conducted before I'd consider buying any Class D amplifier, not just yours, simply because, as a purist, the noise issue worries me:)
Marco
The amplifier in room we used at Cranage was a TAD Implementation of a pwm switching amplifier their own technology again 5th harmonic bandwidth and a very good example
Thanks for that, but was it Class D, or if not, what? Sorry, I don't know what "pwm" is.
Marco.
Hi Marco
Not a problem, if a PWM (Pulse width modulation) amp. Class 'd' is purely is fed by a digital input only, things like the TACT and Devialet use internal A2D to convert the incoming analogue signal to digital then through the module and a low pass filter to take out any unwanted high frequencies artifacts.
A PWM can take analogue inputs without any A2D conversion.
PWN are not strictly Class 'D'
I have no problem in comparing these amps to traditional class a/b valves or a for that matter (with zero mains conditioning), as with everything if you pay careful attention to all of the issues within a design of this kind, especially RF propagation both external and internal you can produce some very pleasing results imho.
This thread has got me all paranoidly worried now.
Hi Marco
Not a problem, if a PWM (Pulse width modulation) amp. Class 'd' is purely is fed by a digital input only, things like the TACT and Devialet use internal A2D to convert the incoming analogue signal to digital then through the module and a low pass filter to take out any unwanted high frequencies artifacts.
A PWM can take analogue inputs without any A2D conversion.
PWN are not strictly Class 'D'
I have no problem in comparing these amps to traditional class a/b valves or a for that matter (with zero mains conditioning), as with everything if you pay careful attention to all of the issues within a design of this kind, especially RF propagation both external and internal you can produce some very pleasing results imho.
Oh no doubt, and that also reflects Anthony's view, plus the limited times I've heard Class D:)
However, it would be interesting carrying out the test I suggested, particularly the measurements, as if anything awry was detected, either there or when listening, then *that* noise/distortion is what's being 'invisibly' superimposed onto the music, simply by way of how Class D works, and which one would be unaware of under normal listening conditions.
Marco.
Hi Marco
Not a problem, if a PWM (Pulse width modulation) amp. Class 'd' is purely is fed by a digital input only, things like the TACT and Devialet use internal A2D to convert the incoming analogue signal to digital then through the module and a low pass filter to take out any unwanted high frequencies artifacts.
A PWM can take analogue inputs without any A2D conversion.
PWN are not strictly Class 'D'
It's only words so not really of any importance but...is there a solid definition of class d? People generally think of class d as denoting a digital amplifier when they are usually PWM. We can also think of "d" the as being a random letter which people then unfortunately ascribe to meaning digital. I think of class d as being predominantly PWM (switching) amps.
anthonyTD
29-01-2019, 11:43
For my part Clive, I appologise, your right, many of us seem to have adopted the D for some reason, to describe all configurations of this topology. :)
It's only words so not really of any importance but...is there a solid definition of class d? People generally think of class d as denoting a digital amplifier when they are usually PWM. We can also think of "d" the as being a random letter which people then unfortunately ascribe to meaning digital. I think of class d as being predominantly PWM (switching) amps.
Marco
I believe you (Anthony) is referring to the high frequency artifacts that are present in the output form all PWM switching type amplifier, if you look at say a 4Khz wave form (sinusoidal) you will see a 'furry' wave form :eyebrows:
This is the result of the switching process which leaves 'noise' on the output, however it is far outside the pass band to be audible after going through the LP filter which is usually set between 50-80Khz
That is very simplified explanation
More in depth below:-
https://www.edn.com/design/consumer/4433820/1/Ternary-modulation-for-Class-D-amps--Part-2-
They are couple of PWM amps on the market which really do not have any 'house sound' they are a close to a straight piece of wire with gain as possible, and have compared these to the DTZ mono's which are pretty much at the pinnacle of commercial available designs.
Whether an individual likes them is just that personal nothing more, if you put 10 people in a room, 5 will say brilliant, 4 will say crap worse ever sound, and the last one will not be able to give an answer until he has consulted his best friend or forum :eek:
Basically technology marches on and materials and components, become, smaller with vastly improved heat dissipation, better form factor, more controllable, better dielectric's, capacitor materials, circuit board layout, better spec's etc.
The future is coming and it is not to far away from many angles not just audio.
It's only words so not really of any importance but...is there a solid definition of class d? People generally think of class d as denoting a digital amplifier when they are usually PWM. We can also think of "d" the as being a random letter which people then unfortunately ascribe to meaning digital. I think of class d as being predominantly PWM (switching) amps.
Clive
Wiki's answer to Class 'd'
The term "class D" is sometimes misunderstood as meaning a "digital" amplifier. While some class-D amps may indeed be controlled by digital circuits or include digital signal processing devices, the power stage deals with voltage and current as a function of non-quantized time. The smallest amount of noise, timing uncertainty, voltage ripple or any other non-ideality immediately results in an irreversible change of the output signal. The same errors in a digital system will only lead to incorrect results when they become so large that a signal representing a digit is distorted beyond recognition. Up to that point, non-idealities have no impact on the transmitted signal. Generally, digital signals are quantized in both amplitude and wavelength, while analog signals are quantized in one (e.g. PWM) or (usually) neither quantity.
hornucopia
29-01-2019, 17:50
....then you get to which speakers you are listening to the resulting sound on/with.
"—it’s amazing how well a superior single driver can perform' I just read (in a review of Nanotech cables!)
which I was agreeing with, as i was listening to my Ocellias for the first time in WEEKS!
We'd better not get started on the effects of cross-overs on the sound!
I agree with Geoff on power consumption, as my Pass F3 uses 250 watts -I think- to produce about 6 o/p!
on we go.
George47
29-01-2019, 18:16
Confusing guys. Class D was the next type of amplifier after Class A, Class B and class C etc. Any additional A/D converters are not necessary or really part of the Class D amplifier but just an additional stage. Class D can be PWM or pulse density modulation.
There has been a great deal of discussion on what the impact of the remnants of the switching frequency has on the audio and what happens to the mains due to the switching noise and the SMPS. Any measurements on distortion normally have to have a filter applied to remove the remnants of the switching otherwise the numberes can become nonsense. Some have argued that applying the output filters to remove the switching frequencies can impact the phase of the audio. A way around this problem has been the deployment of new GaN rather than Mosfets, which are operated at a much higher switching frequency. There are a few GaN amplifiers around and some have been very impressed with them. Bruno Putzeys was less impressed with GaN when I recently talked to him. Not needed.
Tony is this a GaN Class D amp?
Hi George
Something a little different, why not pop over and have a listen it may cause you to think somewhat it is. The evolution of the one we discussed at the show back in October
Tradition FET's even the new SIC types still have limitations and banks of FET's again gave there own issues in balancing, feed rail supplies, heat sink space etc
Remember the power supply on a pwm has to absorb a percentage of the output power (with a full bridge thats both rails)as one of its has traits along with aligning clock speeds along with particular null point in the switching spectrum that suits the particular module being used
The older t class used to switch around 1.2-1.4mhz and they used just one pair of FET's per channel to respectable effect
There is no black art here just common sense, and looking at the design from all aspects and taking your time to truly understand how and why each piece of puzzle has a direct effect on the soun. Also employing the services of an RFI engineer to help assess the impact of said design within the constraints of the what effect said interference has while also keeping within the boundaries of the CE regulations for such products
Sounds interesting.
I was convinced that PWM amps had a bright future when I heard the TAD PWM amps driving their speakers at a show about 3 years ago. The speed, openness, fluidity and detail was breathtaking (helped of course by the TAD speakers).
Tony I had a look at your website for more details of your PWM implementation, such as form, specs, price and pictures, but did not see anything. Any chance please of putting something up (here, on your website or directly to me) please?
Cheers
Edward
montesquieu
29-01-2019, 23:36
Sounds interesting.
I was convinced that PWM amps had a bright future when I heard the TAD PWM amps driving their speakers at a show about 3 years ago. The speed, openness, fluidity and detail was breathtaking (helped of course by the TAD speakers).
Tony I had a look at your website for more details of your PWM implementation, such as form, specs, price and pictures, but did not see anything. Any chance please of putting something up (here, on your website or directly to me) please?
Cheers
Edward
I had a Lyngdorf PWM power amp a few years back and thought it was pretty good with a Tannoys. I’m sure the technology has come a long way since that amp which was already an older model. Be interesting to see where this goes.
Edward
It is a brand new design currently testing with some respected beta testers in different systems across the uk, there are three amplifier designs currently. We have been testing the water for six months but these amplifiers have taken twelve years to come to fruition.
These will be 100% UK manufactured and built, the amps are called liquid music the clue is in the title I firmly believe we have now got so close to 2A3 fluidity without the draw backs it is worth bring to the attention of people.
Those that have listened to them have demonstrated immediate interest and the majority have been high quality valve owners, hence why we are taking this further.
It is not a magic bullet or will appeal to everyone, however those are are really interested in truer reproduction of recorded sounds will seek out an audition, whether they wish to take further will be a personal choice nothing more as with everything in audio your ears and sysyem will tell you if it is right for you and you alone.
I take it you were referring to the Windsor show a few years back Edward?
Tad speakers are superb, however you get what you put in and some amplifiers just do not deliver the results you would expect, a few well know pwm models among them.
We have a demonstration which maybe available for those interested in trying out these amps, I would suggest a pm rather than clogging up this thread
Edward
That particular amp was residing in a system very close to you up until a few weeks it is a shame you could have dropped in on that system and listened for yourself
Thanks Tony for your most comprehensive response. Yes it was at the Windsor show about 3 years ago and since then in Munich the TAD experience confirmed the view.
Edward
Discopants
31-01-2019, 22:03
I had a Lyngdorf PWM power amp a few years back and thought it was pretty good with a Tannoys. I’m sure the technology has come a long way since that amp which was already an older model. Be interesting to see where this goes.
I splurged on a black Friday deal TDAI3400 , its bloody brilliant bit of kit, very musical and the DSP is incredible. I only stream spotify and listen to you tube and TV via an apple TV. So its almost a one box solution. I cant detect any noise in the TV or the apple TV or the subwoofer from the switched mode power supply either audibly or visually.
So I have had on test for about a week now Tony's LM1 version of his PWM amp. In a short sentence the experience has been stunning - and highly disruptive.
Stunning in the liquidity, detail, speed it is able to perform. Disruptive in the sense it has taken me so far down the road as to what I thought an amp is able to do.
The amp Tony lent me is his smallest amp being 85w, the next ones up are a 125w and then 220w monos.
I have thrown everything I can at the amp and without fail it just gets on with the job. Absolutely sublime sound. I simply can't fault it.
Massive grip as well as stunning shimmering highs. The detail and speed are the major magic of the amps. But also the overall coherence, things are 'just right'.
I've had the amp driving Tannoy Eatons and Kudos Cardeas - both are handled magnificently by the LM1. The music is delivered perfectly. I've been listening to albums I know very well and hearing them in a radically new light. The detail that is extracted is so refined that one can almost visualise the instruments being played. Soundstage is deep, wide and high. Pinpoint accuracy. Totally non fatiguing. Highly emotional.
Tried various preamps and again the LM1 faithfully and honestly delivers the sound.
Adam (westlower) has heard this amp in an extended listening session as well. He can report on his views separately, but I did see a wide smile from him when he was listening.
Tony says he has some further 'tuning' he can do which will deliver 20% more. I can't imagine how it is possible.
Sadly the loan will end sometime this week.
Firebottle
11-02-2019, 07:08
Maybe Mr. C should now be called Mr. D :D
Fantastic amp.
Maybe Mr. C should now be called Mr. D :D
Fantastic amp.
Indeed Alan. Just listening to some stuff right now whilst waiting for the young lady (aka the Finance Director) before we head out. Some Bach Cello stuff, what I failed to mention before is the texture this amp is able to convey. Not only the instrument itself (you can make out the differences between the notes produced by the wood and the drawing of the bow) but also the layered nature of the other instruments as well as the micro-detail coming through from the recording room. Realism rools ok! :)
bungalowbill
11-02-2019, 13:56
Interesting.
I've heard a fair few class d amps and while there was a wide range of presentations and excellence they all had a characteristic smoothing over of the finer details.
I guess the Coherent amps have overcome this?
You certainly have. Still using the Lyngdorf SDA2175 you sold me and the A1 FBP Pre. 😊
WESTLOWER
12-02-2019, 16:52
So I have had on test for about a week now Tony's LM1 version of his PWM amp. In a short sentence the experience has been stunning - and highly disruptive.
Stunning in the liquidity, detail, speed it is able to perform. Disruptive in the sense it has taken me so far down the road as to what I thought an amp is able to do.
The amp Tony lent me is his smallest amp being 85w, the next ones up are a 125w and then 220w monos.
I have thrown everything I can at the amp and without fail it just gets on with the job. Absolutely sublime sound. I simply can't fault it.
Massive grip as well as stunning shimmering highs. The detail and speed are the major magic of the amps. But also the overall coherence, things are 'just right'.
I've had the amp driving Tannoy Eatons and Kudos Cardeas - both are handled magnificently by the LM1. The music is delivered perfectly. I've been listening to albums I know very well and hearing them in a radically new light. The detail that is extracted is so refined that one can almost visualise the instruments being played. Soundstage is deep, wide and high. Pinpoint accuracy. Totally non fatiguing. Highly emotional.
Tried various preamps and again the LM1 faithfully and honestly delivers the sound.
Adam (westlower) has heard this amp in an extended listening session as well. He can report on his views separately, but I did see a wide smile from him when he was listening.
Tony says he has some further 'tuning' he can do which will deliver 20% more. I can't imagine how it is possible.
Sadly the loan will end sometime this week.
Well, I had this amp in my system for a few hours, firstly it really sounds superb, with great grip on the low end and dynamics and sparkle to hanker after. What you'd expect I suppose.
It was a relatively short listening time but it grew and opened up as the time passed.I had a preconcieved idea of what to expect and I was right in it's ability to effortlessly push
more from the system. But what i hadn't figured was it's ability to sound cultured and unctuous. So I was pretty impressed to say the least. It really finds detail and portrays
ambience well. I can see how this addictive sound could well be a game changer...
I personally wouldn't swap it now for my tubes as i require something else. But that's just me and my quest for capturing atmosphere of the era.
One thing we did find, in my system, was to be careful about material selection. Playing Tidal MQA Masters, the pianos became slightly jarring, we switched to rebook of the same Album and
that was far more palatable. But as i say this could well be synergy with other components in my set up.
I have previously experienced a Nord Acoustics Class D power amp on duty and was very impressed with that also. This PWM amp has a touch more of the nice stuff around the midrange.
Anyway I was impressed and was totally blind to the price point, or indeed the product really. Edward turned up with a non descript box and plugged it in.
I can see the future.....Class D is surely in that picture somewhere.
montesquieu
12-02-2019, 17:06
On reports from Edward and Adam, I'm very keen to hear this. Coherence ... cultured ... unctuous .. shimmering ...liquidity ... all hitting the right spot for me.
Interesting about the Tidal MQA content, MQA is an interesting topic at the minute - could be that whatever 'enhancements' are baked in with MQA, this amp is sensitive enough to pick up as overdone?
WESTLOWER
12-02-2019, 17:29
On reports from Edward and Adam, I'm very keen to hear this. Coherence ... cultured ... unctuous .. shimmering ...liquidity ... all hitting the right spot for me.
Interesting about the Tidal MQA content, MQA is an interesting topic at the minute - could be that whatever 'enhancements' are baked in with MQA, this amp is sensitive enough to pick up as overdone?
This was my thinking too. The MQA Masters thing is interesting, for me, modern recorded LPs such as those on the already wonderfully recorded, ECM label don't need extra enhancements.
It can easily go too far.
I don't think the aim of MQA is to 'enhance' stuff, simply to take music that is recorded at higher than Redbook standard and, by switching and 'folding' frequencies it is able to pack it in a standard Redbook PCM stream (as well as 'authenticating') the source. I think what Adam and I heard was the farting around with freqs that MQA employed such that the unfold was not faithful to the original. Tony's amp, with its resolving abilities, was able to clearly show this. The Redbook version was unquestioningly better for the 4 ears employed in the session.
WESTLOWER
12-02-2019, 17:57
IMHO The amp is certainly an achievement, i have to say.
I don't think the aim of MQA is to 'enhance' stuff, simply to take music that is recorded at higher than Redbook standard and, by switching and 'folding' frequencies it is able to pack it in a standard Redbook PCM stream (as well as 'authenticating') the source. I think what Adam and I heard was the farting around with freqs that MQA employed such that the unfold was not faithful to the original. Tony's amp, with its resolving abilities, was able to clearly show this. The Redbook version was unquestioningly better for the 4 ears employed in the session.
It could well be the imperfect unfold causing the issue, but an MQA file is still larger than a red book file I think. I also think they do eq it to make it sound slightly different, although with a proper unfold that should not sound 'bad'.
montesquieu
12-02-2019, 19:00
It could well be the imperfect unfold causing the issue, but an MQA file is still larger than a red book file I think. I also think they do eq it to make it sound slightly different, although with a proper unfold that should not sound 'bad'.
Yes but really any machine-instigated dicking around with the signal is unwanted, full stop.
It could well be the imperfect unfold causing the issue, but an MQA file is still larger than a red book file I think. I also think they do eq it to make it sound slightly different, although with a proper unfold that should not sound 'bad'.
It was not bad as such, just that the Redbook version was 'nicer'. There was a passage in particular that Adam and I concentrated on, the Redbook won the day. But of course, by definition, the two versions were different. The Redbook was either downsampled from the higher res version (that the MQA version was folded from) or they were different masters. Beyond that, even though I've tried to understand the maths behind MQA, it is all beyond me (thank gawd). :)
Yes but really any machine-instigated dicking around with the signal is unwanted, full stop.
Well purism of course is a honourable pursuit Tom and I for one would always try to stick to that road when I can (e.g. liking NOS Dacs). However recently I have been 'dicking' around with DSP room filters and the results so far are very encouraging.
Just to be provocative (and also friendly!) isn't implementing an RIAA curve on vinyl tantamount to 'dicking around with the signal'? :)
montesquieu
12-02-2019, 19:34
Just to be provocative (and also friendly!) isn't implementing an RIAA curve on vinyl tantamount to 'dicking around with the signal'? :)
The RIAA curve is a global standard (set in the US) which sets out the precise way a recording needs to be processed to get it to fit in a groove playable by a stylus.
Without encoding in this way (effectively, reducing the amplitude of bass frequencies by particular proportions around a particular frequency) then a standard groove width would be impossible (or at least a standard groove width that had a decent frequency range). Of course once encoded on the record, in order to be played back this encoding has to be decoded, or 'equalised' by boosting bass frequencies in an inverse curve to that applied when the master stamper was prepared.
Some kind of signal encoding was applied to 78s as early as the 1920s, and throughout the era of 78s and early LPs, every company - Columbia, HMV, Victor, Parlophone etc - had their own version in the form of different turnover and rolloff points. Some early preamps had controls that allowed these to be varied by record label.
The situation was standardised under RIAA (Recording Institute of America) auspices in 1956 and became a global standard (turnover point and rolloff amount). This in turn allowed phono preamps to be standardised too, so nearly all modern ones don't have options to vary the parameters of the curve.
Some specialised ones such as the Slee Jazz Club do, however, and these can be used for archiving or for direct playback of early cuts that use pre-RIAA encodiing/equalisation.
Anyway, it's not really dicking about, to answer your question as it's inherent in all vinyl replay and, in modern times, standardised.
Playing devils advocate here Tom, MQA are trying to establish a global standard as well, just as RIAA did all those years ago. But imo MQA is a solution to a non existent problem.
Thanks for details of RIAA.
Looking forward to having a listen to the Silvercores soon btw.
montesquieu
12-02-2019, 19:46
Playing devils advocate here Tom, MQA are trying to establish a global standard as well, just as RIAA did all those years ago. But imo MQA is a solution to a non existent problem.
Thanks for details of RIAA.
Looking forward to having a listen to the Silvercores soon btw.
It's not a non-existent problem if you are a giant copyright owner worried about the amount of digital content out there they don't have control over. Rights management - cui bono?
Just tell them to naff off!
Oops - I meant a non existent problem from the consumer's perspective.
jandl100
12-02-2019, 19:52
You certainly have. Still using the Lyngdorf SDA2175 you sold me and the A1 FBP Pre. ��
Ha!
Excellent.
Nice bits of kit, good that you are still enjoying them! :)
jandl100
12-02-2019, 19:53
Just to be provocative (and also friendly!) isn't implementing an RIAA curve on vinyl tantamount to 'dicking around with the signal'? :)
Yes.
But it would sound rubbish if you didn't dick around with it.
montesquieu
12-02-2019, 20:01
Yes.
But it would sound rubbish if you didn't dick around with it.
More concise than my version but just as accurate!
IWell purism of course is a honourable pursuit Tom and I for one would always try to stick to that road when I can (e.g. liking NOS Dacs). However recently I have been 'dicking' around with DSP room filters and the results so far are very encouraging.
Just to be provocative (and also friendly!) isn't implementing an RIAA curve on vinyl tantamount to 'dicking around with the signal'? :)
An NOS DAC is technically less accurate than one that oversamples, so less purist. DSP is correcting the frequency response anomalies caused by the room and/or loudspeakers. So arguably purist. :)
An NOS DAC is technically less accurate than one that oversamples, so less purist. DSP is correcting the frequency response anomalies caused by the room and/or loudspeakers. So arguably purist. :)
Good grief Martin, you are like my wife - telling me I've got everything the wrong way round. You are both correct of course! :lol::lolsign:
Must be my feminine side coming out...
MQA a solution to a problem that does not exist. Ex Meridian employee's attempting to pervert the course audiofoolery.
I have around fifty MQA files, many of them I also have in various sample rates and bit depth (more important), and they do sound different, just like DSD the upper frequencies have been manipulated to give a more 'pleasing' sound to the masses and give audiophiles some to discuss other than the hoppiness of Hook Norton ale.
Do the sound any better, not a chance in luke warm knitting circle. Different yes, better NO sirree Bob.
I've got this picture in my head Tony of old ladies in a circle doing some knitting and drinking from some barrels of Hook Norton ale. Hope the knitting patterns hold up. :lol:
MQA a solution to a problem that does not exist. Ex Meridian employee's attempting to pervert the course audiofoolery.
I have around fifty MQA files, many of them I also have in various sample rates and bit depth (more important), and they do sound different, just like DSD the upper frequencies have been manipulated to give a more 'pleasing' sound to the masses and give audiophiles some to discuss other than the hoppiness of Hook Norton ale.
Do the sound any better, not a chance in luke warm knitting circle. Different yes, better NO sirree Bob.
tis an opinion, and only that tho. for every one who dislikes it, 10 seem to like it; or they will go bust.(which of course they might) I like tidal and i like qoboz... i even quite liked spotify, although for differing reasons for all i guess. as for audiofoolery, well i will leave that
Hi Grant
You are correct, it is an opinion and one that divides the pro audio community, The streaming services are a different matter, MQA is purely a so called lossless format. More CAMERA appreciation ladies I feel :lol:
For general listening I use Spotify no problem at all.
realysm42
16-02-2019, 04:00
I paid a visit to Tony last year whilst on holiday in England, his setup then I believe was a WIP with the class D amps mentioned here. It's the best sounding set up I've heard, exceptionally impressive.
Hi Mark
Thank you for your comments, however no that was a previous version of said pwm amplifier, SQ has moved on quite markedly since then.
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