The questioner is confused. The “D” in Class D does not stand for “Digital”. The “D” just happens to be the next letter in sequence for amplifier types.
@@AccuphaseMan Many people are confused by the Class D name. A digital electronic device processes Binary Digits or Bits, usually 0’s and 1’s. A Class D amplifier does not process Bits. It is a Pulse Width Modulation device so a better name would have been Class P for PWM.
This is a nice explanation, it actually allows us to imagine what a digital amplifier looks like. A class D amp takes an analog input signal and converts the signal strength in a duty cycle i.e. pulse width modulation, as Paul says. A Digital amplifier takes the digital signal, what ever it is, and converts that directly in a pulse width modulation. At the output transistors, it is different from a class D becasue that time domain is pure analog. With a digital amplifier the time domain will be divided by a clock signal to give a fixed integer number of the sum of on and off states per cycle. I think that will be coming our way in the future. BTW, the "filter" at the output of a class D is acting as integrator. By integrating the duty cycle of one cycle, that PWM signal is converted back in to an amplitude level.
Correct but one little nit ... _"With a digital amplifier the time domain will be divided by a clock signal to give a fixed integer number of the sum of on and off states per cycle. "_ It should actually say "number of cycles per on and off state." In the digital input version the PCM sample is used to count down to 0 before switching the output state.
At my live blues music venue, I use QSC K12.2s, KS118, and CP12s. All Class D powered speakers. My lights are all LEDs too. My venue is in a very old building in Japan. In three years I've never had the power cut out. Not once. Musically speaking, we have a great speaker setup and very good room treatment. Our mixer is an analog Midas Venice 240 and everything else in the chain is all analog too. Man, I'm telling you that the sound is amazing! Even when I play CDs through my 1989 Yamaha CD player, the sound is tight in the room. I would seriously compare my music playback to that of a high end home audio setup. No joke! We've maximized the sound quality of the QSC speakers because of our overall setup. I own a Yamaha B-2 (Class A) at home. So I can definitely tell a difference in tone albeit its apples to oranges between the purpose of both rooms. While I'm definitely loving both Class A and D amps, I've mostly experienced that room setup makes the biggest difference. That's the ONLY way to get one's moneys worth from expensive gear. As Paul says, spend most of your money on speakers, then amp, then...etc. And I say spend most of your time and effort on room setup. Homemade sound absorbers made with rolled fiberglass and thin black cotton material stapled to a light wood frame changed my life and and the sound of my venue. I can't wait to make some for my listening room at home. For live music, Class D QSC speakers are the creme of the crop! Setup setup setup!
One of my quick and dirty tests to see if the sound system isn't crap and the acoustics are okay is to have a conversation with someone while music plays loudly. With a well setup system you can still crank it loud and talk to people a lot more easily than a system with poor acoustics and amps/speakers. I'm sure other people here have experienced the same phenomenon!
@@bf0189 Yes! Visit a concert in a stadium (not designed for music) and it's hard to have a conversation. Visit a concert at a music hall designed for the best possible acoustics, it's not as hard to speak to people as at the stadium. The same at party's or at a bar where they're playing loud music. You will notice the difference in your ability to have a conversation or not depending on the quality of their PA system.
@@hugoromeyn4582 I noticed that at the age 16 when my dad switched from a Marantz surround sound receiver to a Emotiva one. The amps in the Emotiva blew away the Marants and allowed my Dad's Axiom speakers to sing. It sounded so clear loud yet I could talk to my dad unlike the Marantz. From there on I became obsessed with audio,. The apple doesn't fall far from the tree
in the 1970's we got a contract from Sylvania to build a 120v 60 Hz source that would supply 750w to drive some AC motors in a tape machine that was going to go into a tracking station for the air force. This would run off 48v DC and had some efficiency requirements so wo could not just build a class AB amp. One of the motors was a synchronous motor so that 60-Z had to be stable within 1% in amplitude and frequency. During design one test we had to pas was driving a heavy duty 3/8" drill with this $20,000 device. In talking to one of Sylvania's engineers during the acceptance tests I asked him why didn't they just specify 48v dc operation for their Ampex FR1100 tape decks? In any case we essentially made a class D amp using 555's, comparators, and op amps in a 1"" 3 unit rackmount form. The breadboard was on a 3x2-1/2 ft piece of plywood and built over a schematic. The hardest part was geting our home brew 60HX oscillator stable over the -55 to +55C operating range. I think we ran the clock at 20KHZ and filtered that out with an LC filter on the output. The test sheet had us record the output for no load full load, high and low DC input levels. We also had to start up that 3/*" drill and put a 3/8" hole in a 1/4" steel - things were very practical in those days. men were men and sheep were scared!
There are actual digital amplifiers that work on the principals of delta-sigma modulation and the bit-stream serves to provide pulse density modulation. It is then noise-shaped and filtered to produce the audio signal to drive the speakers. I don't know of that many examples offhand, but it has been around for at least ten years or more. However, pretty much all other class-D amplifiers are actually analog as there is usually some form of comparator, waveform generator, and other analog circuitry to derive the PWM or similar signal that is then filtered to get the audio signal to drive the speakers. The big difference is that they are not _linear_ as there is non-linear switching involved unlike class-AB which the transistors basically just act as variable resistors to regulate how much current can flow into the load.
@@kkrobertson1 His explanation was not quite correct. He tried to draw some parallels between the switching to drive a load and binary logic, and said that PWM class-D is not quite analog. Contrary to that, it is very much fully analog in nature. I originally tuned in since PS Audio does use the delta-sigma technique I mention above in one of their DACs, but he only brought it up in passing even though it would have been instructive to hear it contrasted with conventional class-D. It would have nicely explained both technologies. Edit: To be fair, he sort of did.
My NAD M2 is one of the few digital amplifiers that was produced. I describe it as a DAC on steroids. There is a white paper describing how it works somewhere on the web.
Paul is correct ... The "D" designation was merely the next letter in the alphabet when assigning amplifier classes. It's like "C" was the next compiler in the sequence of development. I've always found the easiest way to understand this is the "FM radio" analogy... The amplifier generates a high powered carrier signal, just like a radio transmitter does. The audio signal is then modulated onto this carrier signal, just like in a radio transmitter. In this case that is accomplished by varying the width of square waves, where in an FM transmitter it is done by varying the frequency of the carrier signal... but the result is the same; a much amplified audio signal riding on a carrier signal. Then, just like any FM receiver, filtering out the carrier wave gives us back the audio signal. The most important take-away here is that at no time is the audio signal "digitized"... Class D amplification is an analog process.
I have the Legacy Audio Wavelet digital pre-amplifier. It does input selection, ADC for analog inputs, tone controls, volume, active cross-over, room-correction, reverberant field recreation, all done in the digital domain. It has 4 output DACs (one for each channel) and sends the signals to power amps.
@@rudolfglaser9664 I use these with active speakers (Legacy Audio Valors) which takes 3 pairs of XLR cables for below 800Hz (with over 2000 watts of internal class-D modules) and a 20 watt tube integrated amp (acting as power amp) for above 800Hz.
@@rudolfglaser9664 Of course, if the post was specifically about power amplifiers, then that is a different matter. As a pre-amplifier, it does change gain (mainly reduction) but in the digital domain, and their is only so much increased gain that can be applied before it clips. This preamp does allow up to a maximum 3dB gain for each output channel (and reduction of 10dB) to level set the drivers (outside of volume control). This is a small level of gain compared to the 24 times gains from the power amplifier sections.
@@rudolfglaser9664 I guess that it also depends on what part of the power-amp is digital. eg. Is it the signal itself that is digital, or is it the microcontroller that controls the switching (in a class-D amp).
NAD made some great "Direct Digital" amps (before mentioned M2 and M32), before moving on to using the Purifi modules in M33. M32 was a Stereophile Class A component and sounds great.
If you wanted brevity, one can say conventional class-D amplifiers are not digital as they do not use a finite state-machine to derive the signals used to generate the PWM. It is done using conventional analog circuitry driven by an analog input, thus they are analog in nature. Just not linear.
While that's a true statement it's not a good explanation as most people without a computer science degree have no idea what a finite state-machine is.
@@G3rain1 While I appreciate Paul “breaking it down” sort of speak, he was not quite correct in his explanation of class-D amps. In his description they are quasi-analog as they are driven by switching circuitry. That is not the case. They are fully analog, and not digital at all. There are, however, actual true digital amplifiers that use delta-sigma to perform pulse density modulation. PS Audio used this same technique in one of their DACs, with the delta-sigma driving an output transformer. It would have been nice to have heard him bring it up in more detail since it uses the same principals.
Hey, can't find the "why does Octave Radio sound so good?" video, but about MP3's, I think they are seriously underrated. Think about it, they allocate more data to the part of the music that needs it, so, in a sense they a kinda have a dynamic digital "swing" - in terms of what the ear/brain, or file type, deems to be more dynamic, say.
Digital is a mathematical concept that we can _map_ onto reality, which is a fundamentally analogue realm. Even a CPU is not really digital, we're just leveraging particular behaviour of transistors that maps well to the concept of digital.
"When an electric charge from the clock’s battery or another power source passes through a crystal it vibrates back and forth, or oscillates, at a set frequency of 32,768 times per second. For every 32,768 oscillations of the crystal, a circuit in the clock, called a counter circuit, counts one second." All digital circuitry begins with pulses from a vibrating crystal. No digital circuit design begins with perfect digital pulses. These pulses are derived from either an AC or DC (Battery) power source.
six decades ago, my physics prof told us, "digital is just a means to efficiently transfer & manipulate the analog world for a variety of functions". he was on Oppenheimer's Manhattan Project team... who was I to argue?
I never liked class D sound, but my last class D amp was more than 10 yrs ago. I hear there has been a lot if improvement since. Might give PSaudio or NAD class D amp a try.
I have had the NAD C388 and it sounded phenomenal, unfortunately it broke down three times so i got my money back and invested in a Rotel pre-power setup.
Indeed there has been significant improvement. These days you could level match an AB and a D amplifier and switch back and forth between them and it's likely you would have to look to see which one is playing.
There are class d amps (Peachtree, Lyngdorf) which have no analog input stage, which can only be connected by SPDIF. That is a bit closer to being “digital”.
@@G3rain1 I agree it isn't in substance "digital". But, since there is no preamp, the volume being controlled in the digital domain, could there be an incremental difference?
That use to be true back in the early days of Class D amplification with switching noise at the the lowest and highest frequencies being the biggest issue but that’s been pretty much tamed now. I would argue that analog amps don’t necessarily sound better than Class D amps - just different. While you can make some very high-powered D amps, they would probably sound the best in low-to-moderate power applications, at least in my experience. I tend to think Class D amps sound “cleaner” (some would say sterile) as compared to the more “warming” presentation of an analog amp. I just don’t think one is better than another - just different. And preferential.
Maybe the real question isn't "which is a digital amp, but does it sound like early digital". When compacts discs first came out, the ones smart enough to hear problems with the sound, pointed out harshness in the highs and a lack of warmth. That is exactly the two main things many people hear and complain of when listening to many Class D amps. If some reviewer's words can be taken for gospel, there are now a few very expensive Class D amps that don't have the above affliction. Which means those things aren't innate with Class D. If many Class D amps sound digital (especially early digital), then you would think they would tonally mate better with analog and it's warmth. Early cd players played through tube amps were listenable. Warmth is very important; make sure you have it in the right amount.
Briefly, Class D amp. is not a Digital amplifier period. Digital amp. or "Power DAC" works that you have a digital signal (PCM) goes to internal DSP chip inside amp who convert PCM signal direct to PWM. Digital part is till PWM section, after PWM is analog. You can't drive speakers with an amplified digital PCM signal. Hence the name Power DAC because it behaves like a DAC, only the output section is a Class D amplifier.
Class D = pulse width modulation. D is next letter in the alphabet after the class C amplifier. Now how many will say no such thing as class C. Dead time in D is also something very important or you get a short circuit.
Described as PWM and either on or OFF, isn't true, somehow you need to get from the ON to OFF, and that is the "dead-band" where we are true analogue. Class D was designed with one aim. Cheap. Uncomplicated output stage, small heatsink. At 6.20 Paul discussed the output filter to "get rid of all the HF noise", however a simple filter won't achieve this, it's on the output stage so needs to take high current which means compromise. IMD distortion is poor there is a list of where Class D goes off the rails. There has been a _lot_ of work to fix the issues inherent in class D, but this is the issue, a design where you need to fix the problems, just go with a design where you are not fighting the topology, but honing what was great to start off with. Industry likes Class D, it's now quite passable, miles from where it was say 15 years ago, it's cheap to make. However for me, it's a dead end technology. Why do you think technical reviews are missing when Class D is reviewed. Because the people who pay for advertising won’t support their products being trashed. This said, who can say that purity is right, maybe a little IMD, compression and distortion sound great to you, and thats OK too.
Lots of people don’t like Digital hardware for their personal stereo system. Tubes will be available for a long time. A/B amplifier’s is another story. I personally prefer A/B amps over Digital. A/B have a different sound signature, tube amps have a different sound signature.
Take a look around ... there are all kinds of detailed technical reviews of Class D amplifiers. A simple search will get you a couple of dozen to look at...
_"somehow you need to get from the ON to OFF, and that is the "dead-band" where we are true analogue"_ Nope. The "dead time" in PWM is both transistors off. If it were otherwise we'd have a dead short across the power supply.
i am puzzled by the SMSL VMV A2 digital amp. it has bluetooth usb optical and coaxial digital inputs but no dac inside?? no need to convert.. it just amplifies that digital signal. all digital. but then it power the speakers.. where is the conversion? there has to be a dac somewhere. but they say no. it also has an analog rca input but it must be digitalized to amplify so they say it has a adc ..but no dac. anyone please??? thanks very much
The conversion is at the output filters ... a simple coil and capacitor circuit much like the low pass on a woofer crossover. The sequence is simple ... accept PCM directly, sample analog inputs up to PCM, manipulate sound in the digital domain, then feed the resulting PCM signals to a PWM (class D) amplifier then finally put it through a low pass filter to remove the PWM carrier.
@@Douglas_Blake_579 This is wrong. It's the same mechanism as a ClassD amp, PWM. But is using a digital logic chip to control the width of the pulses instead of an analog comparator. You can't just feed PCM into an amp chip, it will just sound like static, it's data and needs to be converted.
I am familiar with Class A, Class A/B, and Class D amps. Not that I really understand the underlying theory behind them. I know that they exist and some general Truths about them. Well, I think they're Truths. The other day I ran across a manufacturer touting their Class G amps. I have absolutely no idea what that is.
Class G employ a multiple DC supply rails to give a boost to higher level signals by increasing the supply voltage momentarily. en.wikipedia.org/wiki/Power_amplifier_classes
There is a major crap-ton of information about Class D on the web. Do some searches and you will find information from beginner to super-expert very easly. I've also offered a slightly different explanation in my other comments here, so you may find some help reading them as well.
It took me an entire year of research before I finally chose my system to buy. It was not just the research , I would think about it for a long time between research with my time. Impulse buying is not a good idea with reviews from others. Take your time.
The D in Class D is for Dirty. I'll stick with my Class A monoblocks. The A stands for Astronomical as in my light bill when I run all five of them in the Summer. Wasn't so bad prior to the 30% increase in rates. Most movies are just fine in stereo and Pink Floyd is worth running all five.
On and off are represented in binary by a 1 and a 0. thats why a 1 and 0 are on basically all power switches, and you perform calculations by carefully controlling how long an individual transistors in a cluster sits in one state or the other.. if its not binary it's not digital? Well by definition of the word digital it can't be, but in my lamens opinion, and because it better suits the way my brain works, im still going to considert them digital whether calculations are being represented by a numerical value or not. It's still an integrated circuit chip that is performing calculations with transistors that can only exist in one of two states. On or Off. This type of amplification is too much for my fried by highschool brain. I barely understand the principles of class A amplification.
They are ... all input signals are internally sampled up to very high sample rate PCM signals, then dealt with in the digital domain. At the power amps the Class D modulators accept PCM inputs and encode directly to PWM which, finally, goes through a filter and on to your speakers.
@@bikdav I suppose it could be seen as that ... but it can also do things a conventional system cannot, such as phase correction, programmable RIAA response curves, room correction, etc.
Well, Paul, any old geezer that spent their life being technical has no problem knowing or understanding what’s going on.. it’s the non-technical under informed old folks and the younger, generations of those that are resistant to theory knowledge or just plain lazy that create all this drama..😂
Indeed ... resistance to knowledge is at the very heart of this problem. I once suggested that a commenter look up "Ohm's Law" ( I = E / R) and got back a huge rant about him not needing to know all that "techy crap" (as he called it) and just wanting to know how power works ... Go figure.
@@Douglas_Blake_579 Yes, for sure, I’ve seen that kind of problem more times than I care to remember too, Doug, which is probably why I felt the inclination to include that in my comment. What really boggles my mind is when I make generalized statements like that one, and someone lashes out at me, as if I targeted them specifically. Strange days indeed that are most peculiar. 😉
@@shipsahoy1793 Yep ... and it's likely to get worse before it gets better. I just don't envy these guys the moment when the facts outweigh convenient fiction.
Calling it "digital", because it is designed with that switching operation, is misleading -- and was probably named "digital" for sales propaganda (people hear "digital" and get excited). I do not know what the name should be. But I know what the name should not be: Digital.
"Class D" got it's name because D was the next available letter of the alphabet in the list of class designations. The whole "digital" thing is one huge misunderstanding of how the device actually works.
Class D is purely digital in the output. It produces a signal that is jagged and stepped, which creates the edginess and harshness that class D is famous for. Either Paul is getting old or he's disingenuous because a digital output is still an electrical signal. Class D amplifiers are purely manufactured e-waste.
@@Paulmcgowanpsaudio I suggest you read an introductory book on electrical engineering and learn about what PWM signals look like on an oscilloscope. It will prevent you from looking misinformed in future.
They are variable length square waves running generally at about 100kHz. You can see the waveforms here: en.wikipedia.org/wiki/Pulse-width_modulation and then see how it works.@@AccuphaseMan
The questioner is confused. The “D” in Class D does not stand for “Digital”. The “D” just happens to be the next letter in sequence for amplifier types.
Class "G" amp would be for old Geezer types
Exactly. And it's a coincidence that has caused no end of confusion among people who think they know without investigating.
That's a load of hogwash
@@AccuphaseMan
Actually, Geoff is correct.
en.wikipedia.org/wiki/Power_amplifier_classes
@@AccuphaseMan Many people are confused by the Class D name. A digital electronic device processes Binary Digits or Bits, usually 0’s and 1’s. A Class D amplifier does not process Bits. It is a Pulse Width Modulation device so a better name would have been Class P for PWM.
Thank you for just being yourself before your audience ❤
This is a nice explanation, it actually allows us to imagine what a digital amplifier looks like. A class D amp takes an analog input signal and converts the signal strength in a duty cycle i.e. pulse width modulation, as Paul says. A Digital amplifier takes the digital signal, what ever it is, and converts that directly in a pulse width modulation. At the output transistors, it is different from a class D becasue that time domain is pure analog. With a digital amplifier the time domain will be divided by a clock signal to give a fixed integer number of the sum of on and off states per cycle. I think that will be coming our way in the future. BTW, the "filter" at the output of a class D is acting as integrator. By integrating the duty cycle of one cycle, that PWM signal is converted back in to an amplitude level.
Correct but one little nit ...
_"With a digital amplifier the time domain will be divided by a clock signal to give a fixed integer number of the sum of on and off states per cycle. "_
It should actually say "number of cycles per on and off state."
In the digital input version the PCM sample is used to count down to 0 before switching the output state.
At my live blues music venue, I use QSC K12.2s, KS118, and CP12s. All Class D powered speakers. My lights are all LEDs too. My venue is in a very old building in Japan. In three years I've never had the power cut out. Not once.
Musically speaking, we have a great speaker setup and very good room treatment. Our mixer is an analog Midas Venice 240 and everything else in the chain is all analog too.
Man, I'm telling you that the sound is amazing! Even when I play CDs through my 1989 Yamaha CD player, the sound is tight in the room. I would seriously compare my music playback to that of a high end home audio setup. No joke! We've maximized the sound quality of the QSC speakers because of our overall setup.
I own a Yamaha B-2 (Class A) at home. So I can definitely tell a difference in tone albeit its apples to oranges between the purpose of both rooms.
While I'm definitely loving both Class A and D amps, I've mostly experienced that room setup makes the biggest difference. That's the ONLY way to get one's moneys worth from expensive gear.
As Paul says, spend most of your money on speakers, then amp, then...etc. And I say spend most of your time and effort on room setup. Homemade sound absorbers made with rolled fiberglass and thin black cotton material stapled to a light wood frame changed my life and and the sound of my venue. I can't wait to make some for my listening room at home.
For live music, Class D QSC speakers are the creme of the crop! Setup setup setup!
One of my quick and dirty tests to see if the sound system isn't crap and the acoustics are okay is to have a conversation with someone while music plays loudly. With a well setup system you can still crank it loud and talk to people a lot more easily than a system with poor acoustics and amps/speakers.
I'm sure other people here have experienced the same phenomenon!
@@bf0189 Yes! Visit a concert in a stadium (not designed for music) and it's hard to have a conversation. Visit a concert at a music hall designed for the best possible acoustics, it's not as hard to speak to people as at the stadium. The same at party's or at a bar where they're playing loud music. You will notice the difference in your ability to have a conversation or not depending on the quality of their PA system.
@@hugoromeyn4582 I noticed that at the age 16 when my dad switched from a Marantz surround sound receiver to a Emotiva one. The amps in the Emotiva blew away the Marants and allowed my Dad's Axiom speakers to sing. It sounded so clear loud yet I could talk to my dad unlike the Marantz. From there on I became obsessed with audio,. The apple doesn't fall far from the tree
in the 1970's we got a contract from Sylvania to build a 120v 60 Hz source that would supply 750w to drive some AC motors in a tape machine that was going to go into a tracking station for the air force. This would run off 48v DC and had some efficiency requirements so wo could not just build a class AB amp. One of the motors was a synchronous motor so that 60-Z had to be stable within 1% in amplitude and frequency. During design one test we had to pas was driving a heavy duty 3/8" drill with this $20,000 device.
In talking to one of Sylvania's engineers during the acceptance tests I asked him why didn't they just specify 48v dc operation for their Ampex FR1100 tape decks?
In any case we essentially made a class D amp using 555's, comparators, and op amps in a 1"" 3 unit rackmount form. The breadboard was on a 3x2-1/2 ft piece of plywood and built over a schematic. The hardest part was geting our home brew 60HX oscillator stable over the -55 to +55C operating range. I think we ran the clock at 20KHZ and filtered that out with an LC filter on the output. The test sheet had us record the output for no load full load, high and low DC input levels. We also had to start up that 3/*" drill and put a 3/8" hole in a 1/4" steel - things were very practical in those days. men were men and sheep were scared!
very cool (or hot, as the case may've been).
that's what it took to win the previous cold war.
There are actual digital amplifiers that work on the principals of delta-sigma modulation and the bit-stream serves to provide pulse density modulation. It is then noise-shaped and filtered to produce the audio signal to drive the speakers. I don't know of that many examples offhand, but it has been around for at least ten years or more. However, pretty much all other class-D amplifiers are actually analog as there is usually some form of comparator, waveform generator, and other analog circuitry to derive the PWM or similar signal that is then filtered to get the audio signal to drive the speakers. The big difference is that they are not _linear_ as there is non-linear switching involved unlike class-AB which the transistors basically just act as variable resistors to regulate how much current can flow into the load.
I believe that what Paul just said in more layman terms.
@@kkrobertson1 His explanation was not quite correct. He tried to draw some parallels between the switching to drive a load and binary logic, and said that PWM class-D is not quite analog. Contrary to that, it is very much fully analog in nature. I originally tuned in since PS Audio does use the delta-sigma technique I mention above in one of their DACs, but he only brought it up in passing even though it would have been instructive to hear it contrasted with conventional class-D. It would have nicely explained both technologies. Edit: To be fair, he sort of did.
My NAD M2 is one of the few digital amplifiers that was produced. I describe it as a DAC on steroids. There is a white paper describing how it works somewhere on the web.
Paul is correct ... The "D" designation was merely the next letter in the alphabet when assigning amplifier classes. It's like "C" was the next compiler in the sequence of development.
I've always found the easiest way to understand this is the "FM radio" analogy...
The amplifier generates a high powered carrier signal, just like a radio transmitter does. The audio signal is then modulated onto this carrier signal, just like in a radio transmitter.
In this case that is accomplished by varying the width of square waves, where in an FM transmitter it is done by varying the frequency of the carrier signal... but the result is the same; a much amplified audio signal riding on a carrier signal.
Then, just like any FM receiver, filtering out the carrier wave gives us back the audio signal.
The most important take-away here is that at no time is the audio signal "digitized"... Class D amplification is an analog process.
Yes!
From one geezer to another, lol, I really love your videos and have learned so much. Thanks Paul.
I have the Legacy Audio Wavelet digital pre-amplifier. It does input selection, ADC for analog inputs, tone controls, volume, active cross-over, room-correction, reverberant field recreation, all done in the digital domain. It has 4 output DACs (one for each channel) and sends the signals to power amps.
Is this really an amplifier - or is it just diverting different inputs to one output and doing some facelifting to it?
@@rudolfglaser9664 I use these with active speakers (Legacy Audio Valors) which takes 3 pairs of XLR cables for below 800Hz (with over 2000 watts of internal class-D modules) and a 20 watt tube integrated amp (acting as power amp) for above 800Hz.
@@rudolfglaser9664 Of course, if the post was specifically about power amplifiers, then that is a different matter. As a pre-amplifier, it does change gain (mainly reduction) but in the digital domain, and their is only so much increased gain that can be applied before it clips. This preamp does allow up to a maximum 3dB gain for each output channel (and reduction of 10dB) to level set the drivers (outside of volume control). This is a small level of gain compared to the 24 times gains from the power amplifier sections.
@@rudolfglaser9664 I guess that it also depends on what part of the power-amp is digital. eg. Is it the signal itself that is digital, or is it the microcontroller that controls the switching (in a class-D amp).
My Technics SU-G700 is a digital amplifier and I love it.
Learn something form you almost every video. Your the Leo Laporte of stereo!
NAD made some great "Direct Digital" amps (before mentioned M2 and M32), before moving on to using the Purifi modules in M33. M32 was a Stereophile Class A component and sounds great.
"Makes" not just "made." I have the M28 5-channel amp with the Purifi magic modules. It sounds great.
@@1Uriahheep1it sounded great. You had to give it back. 😢
@1Uriahheep1 I have looked at the M28 and it's a 7 channel receiver not a 5 channel.
Brilliant explanation, thank you.
If you wanted brevity, one can say conventional class-D amplifiers are not digital as they do not use a finite state-machine to derive the signals used to generate the PWM. It is done using conventional analog circuitry driven by an analog input, thus they are analog in nature. Just not linear.
While that's a true statement it's not a good explanation as most people without a computer science degree have no idea what a finite state-machine is.
@@G3rain1 While I appreciate Paul “breaking it down” sort of speak, he was not quite correct in his explanation of class-D amps. In his description they are quasi-analog as they are driven by switching circuitry. That is not the case. They are fully analog, and not digital at all. There are, however, actual true digital amplifiers that use delta-sigma to perform pulse density modulation. PS Audio used this same technique in one of their DACs, with the delta-sigma driving an output transformer. It would have been nice to have heard him bring it up in more detail since it uses the same principals.
Hey, can't find the "why does Octave Radio sound so good?" video, but about MP3's, I think they are seriously underrated. Think about it, they allocate more data to the part of the music that needs it, so, in a sense they a kinda have a dynamic digital "swing" - in terms of what the ear/brain, or file type, deems to be more dynamic, say.
Digital is a mathematical concept that we can _map_ onto reality, which is a fundamentally analogue realm.
Even a CPU is not really digital, we're just leveraging particular behaviour of transistors that maps well to the concept of digital.
"When an electric charge from the clock’s battery or another power source passes through a crystal it vibrates back and forth, or oscillates, at a set frequency of 32,768 times per second. For every 32,768 oscillations of the crystal, a circuit in the clock, called a counter circuit, counts one second."
All digital circuitry begins with pulses from a vibrating crystal. No digital circuit design begins with perfect digital pulses. These pulses are derived from either an AC or DC (Battery) power source.
six decades ago, my physics prof told us, "digital is just a means to efficiently transfer & manipulate the analog world for a variety of functions". he was on Oppenheimer's Manhattan Project team... who was I to argue?
Great reply! It was around that time that I started out in engineering school but never heard a statement like that. Professors can be prophetic.
Most Class D amplifiers do not use a crystal oscillator.
I never liked class D sound, but my last class D amp was more than 10 yrs ago. I hear there has been a lot if improvement since. Might give PSaudio or NAD class D amp a try.
I have had the NAD C388 and it sounded phenomenal, unfortunately it broke down three times so i got my money back and invested in a Rotel pre-power setup.
Indeed there has been significant improvement. These days you could level match an AB and a D amplifier and switch back and forth between them and it's likely you would have to look to see which one is playing.
There are class d amps (Peachtree, Lyngdorf) which have no analog input stage, which can only be connected by SPDIF. That is a bit closer to being “digital”.
Not really, that's just a DAC and an AMP in one box. The class D amplifier IS receiving analog input. it's just coming from the paired internal dac.
@@G3rain1 I agree it isn't in substance "digital". But, since there is no preamp, the volume being controlled in the digital domain, could there be an incremental difference?
Cool to see an instrument in a video :) Anyone know what guitar that is? ❤
Analogue amplifiers are free from the complex signal processing of digital or the usual class D types which is why they sound better.
That use to be true back in the early days of Class D amplification with switching noise at the the lowest and highest frequencies being the biggest issue but that’s been pretty much tamed now. I would argue that analog amps don’t necessarily sound better than Class D amps - just different.
While you can make some very high-powered D amps, they would probably sound the best in low-to-moderate power applications, at least in my experience. I tend to think Class D amps sound “cleaner” (some would say sterile) as compared to the more “warming” presentation of an analog amp. I just don’t think one is better than another - just different. And preferential.
The little matter that Class D has reduced parts counts significantly, notwithstanding.
@@Douglas_Blake_579 indeed. And they're lighter and more efficient than your standard analog amps.
For low cost and power class d chip amps the speaker is driven directly (Analog devices/ Maxim ) come to mind. More for the mobile market.
Maybe the real question isn't "which is a digital amp, but does it sound like early digital". When compacts discs first came out, the ones smart enough to hear problems with the sound, pointed out harshness in the highs and a lack of warmth. That is exactly the two main things many people hear and complain of when listening to many Class D amps. If some reviewer's words can be taken for gospel, there are now a few very expensive Class D amps that don't have the above affliction. Which means those things aren't innate with Class D. If many Class D amps sound digital (especially early digital), then you would think they would tonally mate better with analog and it's warmth. Early cd players played through tube amps were listenable. Warmth is very important; make sure you have it in the right amount.
Briefly, Class D amp. is not a Digital amplifier period. Digital amp. or "Power DAC" works that you have a digital signal (PCM) goes to internal DSP chip inside amp who convert PCM signal direct to PWM. Digital part is till PWM section, after PWM is analog. You can't drive speakers with an amplified digital PCM signal. Hence the name Power DAC because it behaves like a DAC, only the output section is a Class D amplifier.
Thank You!
Class D = pulse width modulation.
D is next letter in the alphabet after the class C amplifier.
Now how many will say no such thing as class C.
Dead time in D is also something very important or you get a short circuit.
Class C is a switching amplifier commonly used for FM radio transmitters.
The output stages in a Class D amplifier actually operate in Class C.
Lyngdorf; Sony (S-Master Pro); Peachtree GAN-1
I love simple questions to
But the answer rarely is simpel 🙄
Lyngdorf?
Described as PWM and either on or OFF, isn't true, somehow you need to get from the ON to OFF, and that is the "dead-band" where we are true analogue. Class D was designed with one aim. Cheap. Uncomplicated output stage, small heatsink. At 6.20 Paul discussed the output filter to "get rid of all the HF noise", however a simple filter won't achieve this, it's on the output stage so needs to take high current which means compromise. IMD distortion is poor there is a list of where Class D goes off the rails. There has been a _lot_ of work to fix the issues inherent in class D, but this is the issue, a design where you need to fix the problems, just go with a design where you are not fighting the topology, but honing what was great to start off with. Industry likes Class D, it's now quite passable, miles from where it was say 15 years ago, it's cheap to make. However for me, it's a dead end technology. Why do you think technical reviews are missing when Class D is reviewed. Because the people who pay for advertising won’t support their products being trashed. This said, who can say that purity is right, maybe a little IMD, compression and distortion sound great to you, and thats OK too.
Lots of people don’t like Digital hardware for their personal stereo system.
Tubes will be available for a long time. A/B amplifier’s is another story.
I personally prefer A/B amps over Digital. A/B have a different sound signature, tube amps have a different sound signature.
Take a look around ... there are all kinds of detailed technical reviews of Class D amplifiers. A simple search will get you a couple of dozen to look at...
_"somehow you need to get from the ON to OFF, and that is the "dead-band" where we are true analogue"_
Nope. The "dead time" in PWM is both transistors off. If it were otherwise we'd have a dead short across the power supply.
My amplifier has an LCD display… so therefore it's a digital amplifier
i am puzzled by the SMSL VMV A2 digital amp. it has bluetooth usb optical and coaxial digital inputs but no dac inside?? no need to convert.. it just amplifies that digital signal. all digital. but then it power the speakers.. where is the conversion? there has to be a dac somewhere. but they say no.
it also has an analog rca input but it must be digitalized to amplify so they say it has a adc ..but no dac.
anyone please??? thanks very much
The conversion is at the output filters ... a simple coil and capacitor circuit much like the low pass on a woofer crossover.
The sequence is simple ... accept PCM directly, sample analog inputs up to PCM, manipulate sound in the digital domain, then feed the resulting PCM signals to a PWM (class D) amplifier then finally put it through a low pass filter to remove the PWM carrier.
@@Douglas_Blake_579 thanks very much
@@Douglas_Blake_579 This is wrong. It's the same mechanism as a ClassD amp, PWM. But is using a digital logic chip to control the width of the pulses instead of an analog comparator. You can't just feed PCM into an amp chip, it will just sound like static, it's data and needs to be converted.
@@G3rain1
There are PWM amplifier chips that accept PCM input directly. The conversion is done internally, usually by calculation of the pulse widths.
@@endrizo
You're welcome
I am familiar with Class A, Class A/B, and Class D amps. Not that I really understand the underlying theory behind them. I know that they exist and some general Truths about them.
Well, I think they're Truths.
The other day I ran across a manufacturer touting their Class G amps. I have absolutely no idea what that is.
Class G employ a multiple DC supply rails to give a boost to higher level signals by increasing the supply voltage momentarily.
en.wikipedia.org/wiki/Power_amplifier_classes
Digital amplifier = Relay
You cannot describe how a Class D amplifier works without using an animated diagram ...
The Audio hardware is like the Drug Dealer.
The end user is the Drug Addict.
Power DAC doesn't exist?
Sales ploy, didn't last long.
I’m gonna be honest with y’all. I didn’t understand a dang thing Paul said here. Pass the dunce cap, please.
There is a major crap-ton of information about Class D on the web. Do some searches and you will find information from beginner to super-expert very easly.
I've also offered a slightly different explanation in my other comments here, so you may find some help reading them as well.
It took me an entire year of research before I finally chose my system to buy.
It was not just the research , I would think about it for a long time between research with my time. Impulse buying is not a good idea with reviews from others. Take your time.
Sharp SM-SX100
The D in Class D is for Dirty. I'll stick with my Class A monoblocks. The A stands for Astronomical as in my light bill when I run all five of them in the Summer. Wasn't so bad prior to the 30% increase in rates. Most movies are just fine in stereo and Pink Floyd is worth running all five.
On and off are represented in binary by a 1 and a 0. thats why a 1 and 0 are on basically all power switches, and you perform calculations by carefully controlling how long an individual transistors in a cluster sits in one state or the other.. if its not binary it's not digital? Well by definition of the word digital it can't be, but in my lamens opinion, and because it better suits the way my brain works, im still going to considert them digital whether calculations are being represented by a numerical value or not. It's still an integrated circuit chip that is performing calculations with transistors that can only exist in one of two states. On or Off.
This type of amplification is too much for my fried by highschool brain. I barely understand the principles of class A amplification.
Then, what is TECHNICS doing? They claim that their new amps - such as the SU-R1000 - are ‘digital.’
They are ... all input signals are internally sampled up to very high sample rate PCM signals, then dealt with in the digital domain. At the power amps the Class D modulators accept PCM inputs and encode directly to PWM which, finally, goes through a filter and on to your speakers.
@@Douglas_Blake_579 All of that just to put out sound? It sounds more complicated than necessary.
@@bikdav
I suppose it could be seen as that ... but it can also do things a conventional system cannot, such as phase correction, programmable RIAA response curves, room correction, etc.
Well, Paul, any old geezer that spent their life being technical has no problem knowing or understanding what’s going on.. it’s the non-technical under informed old folks and the younger, generations of those that are resistant to theory knowledge or just plain lazy that create all this drama..😂
Indeed ... resistance to knowledge is at the very heart of this problem.
I once suggested that a commenter look up "Ohm's Law" ( I = E / R) and got back a huge rant about him not needing to know all that "techy crap" (as he called it) and just wanting to know how power works ... Go figure.
@@Douglas_Blake_579 Yes, for sure, I’ve seen that kind of problem more times than I care to remember too, Doug, which is probably why I felt the inclination to include that in my comment. What really boggles my mind is when I make generalized statements like that
one, and someone lashes out at me, as if I targeted them specifically. Strange days indeed that are most peculiar. 😉
@@shipsahoy1793
Yep ... and it's likely to get worse before it gets better.
I just don't envy these guys the moment when the facts outweigh convenient fiction.
Calling it "digital", because it is designed with that switching operation, is misleading -- and was probably named "digital" for sales propaganda (people hear "digital" and get excited).
I do not know what the name should be. But I know what the name should not be: Digital.
"Class D" got it's name because D was the next available letter of the alphabet in the list of class designations. The whole "digital" thing is one huge misunderstanding of how the device actually works.
Oxymoron
I don't understand any of this stuff it's like you're speaking an alien language
Class D is purely digital in the output. It produces a signal that is jagged and stepped, which creates the edginess and harshness that class D is famous for. Either Paul is getting old or he's disingenuous because a digital output is still an electrical signal. Class D amplifiers are purely manufactured e-waste.
Not ....... even ...... close.
@@Douglas_Blake_579 Cope, Seethe and Mald harder
I have no idea what you are talking about. Class D is Pulse Width Modulation. No jagged stairsteps.
@@Paulmcgowanpsaudio I suggest you read an introductory book on electrical engineering and learn about what PWM signals look like on an oscilloscope. It will prevent you from looking misinformed in future.
They are variable length square waves running generally at about 100kHz. You can see the waveforms here: en.wikipedia.org/wiki/Pulse-width_modulation and then see how it works.@@AccuphaseMan