O.k, let it be switching even with no input signal. Still, this does not devaluate my proof, that an important characteristicum of Class-D is switching range.
O.k, Mister Semantic: Without input signal, only carrier is switched. Since carrier is filtered away before load, no current flows. But Class-D means to switch the signal, the load.
Where did I wrote you denied that? Nowhere.
In #82 you wrote: "Anything using PWM is by definition analogue. " I was quoting your statement directly above my question, very hard to not understand the relation.
With exactly the same logic you could also tell J1850 is analog. It is used to transfer originally analog operation parameters (temperature, speed, etc...) to OBD displays in cars. So do you think J1850 was analog?
That's arguably an accident of cost effective implementation. Consider these cases, a Raspberry Pi used as a convenient stand-in for any generic computing platform:
- A Raspberry Pi uses internal software to generate the IR codes controlling a TV and feeds a PWM modulator
- That software is closed and software generating a calculated sequence of numbers representing the amplitude of a sine wave feeds the PWM modulator
- The sine wave software is closed and replaced by software reading a sequence of numbers representing the amplitude of an audio file from the internal drive, feeding the same PWM modulator
The only change is the 'data' presented to the modulator. Is the overall system digital, analogue or is it determined by the signal feeding the PWM modulator? As stated earlier I honestly consider it one of those intriguing edge cases and don't expect this thread will ever settled on an agreement.
Standard disclaimer, I agree all Class D amps are (likely) analogue devices.
In post 82 I saidPafi said:
I subsequently clarified in post 97:DF96 said:
PWM is an analogue technique, but it can be used for digital purposes - just as a voltage is an analogue quantity but can be used for digital purposes.DF96 said:
I know nothing of J1850, so I am not in a position to comment. In any case, what relevance does it have?Pafi said:
Class D takes a voltage (analogue quantity), forms a pulse width (analogue quantity), then passes it through a low pass filter to get a voltage again (analogue quantity). No numbers. No coding or decoding. No arithmetic. No algorithms. No logic gates. No FIFOs. No shift registers. No ALU. In what sense is this digital?
I am not saying that anything which uses an analogue technique (such as PWM) is necessarily analogue, but I am saying that something which uses only analogue techniques and no digital techniques must be analogue. Unless, of course, you believe that a system containing no digital techniques or functions can somehow be digital?
What you told is true for SOME MEMBERS of ClassD. BUT when we say digital amplifier WE ARE TALKING NOT ABOUT THIS KIND OF MEMBERS of ClassD, but such members that use digital signal processing like registers, DIGITAL comparator (one flag of an ALU in connection with subtraction is sign bit), and for good resolution txpically a noise shaper (also with only digital circuits, registers, adders, multipliers). Input is digital also. Not a single element is required to be analog, except output filter, but it is also can be omitted. So in this sense this KIND OF AMPlifiers are called digital, NOT a Class containing them.
The original claim, as I recall it, is that Class D is digital. I am glad you accept that this is, in general, not true. A digital front end producing a PWM signal which then goes to a Class D output stage is in my view a mixed-type of amplifier, as the output stage is still analogue. I realise that for marketing purposes this will be called digital.Pafi said:
Having cleared that up, can we get back to the main topic of this thread?
Again, TAS5001.
Class-T is a marketing trick. It is a member of Class D.
https://en.m.wikipedia.org/wiki/Class-T_amplifier
Class-T is a marketing trick. It is a member of Class D.
https://en.m.wikipedia.org/wiki/Class-T_amplifier
No it's not. Tri-Path ("class T") may be called a digital amplifier as it contains an ADC and and power DAC (output stage topology, not stereo system component!). As such it has a completely different approach to amplification and would/could be seen as a different class of amps however it is not officially classed.
According to Wiki... "A "Class D" amplifier uses some form of pulse-width modulation to control the output devices".
There is no PWM in "Class" T.
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According to Wiki... "A "Class D" amplifier uses some form of pulse-width modulation to control the output devices".
There is no PWM in "Class" T.
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This component has a digital interface. It is not a digital PWM amplifier which was what I was asking about.
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As I already recognized we don't speak the same language. You wrote "one that is digital". I named one. And now you pretend that you asked something different.
Your ask is irrelevant. Your example of Tripath is already an exception from the imagined rule of "all ClassD is analog". I don't have to list all of the exceptions. Your condition of being PWM is irrelevant. PWM is NOT a neccessary operation mode for ClassD devices, it is only an example, absolutely not required for being ClassD. Only one condition is needed for an amp to be ClassD: switch mode.
Your ask is irrelevant. Your example of Tripath is already an exception from the imagined rule of "all ClassD is analog". I don't have to list all of the exceptions. Your condition of being PWM is irrelevant. PWM is NOT a neccessary operation mode for ClassD devices, it is only an example, absolutely not required for being ClassD. Only one condition is needed for an amp to be ClassD: switch mode.
http://www.ti.com/lit/ds/symlink/tas5001.pdf
It's in the headline:
"TRUE DIGITAL AUDIO AMPLIFIER
TAS5001 DIGITAL AUDIO PWM PROCESSOR."
Can you tell me what is your problem exactly?
No, never. Jan said "nothing digital in Class D". I denied this. (=there is something digital in ClassD).
I'm glad that after several pages you maybe realized what the debate you participated is about. Now you may be able to re-read, and correct your mistakes.
Output stage is as analog as a logic gate. You can call a logic gate analog, this is your choice. If I was forced to tell if it's digital or not, I prefer telling it based on the signals. When the signal carrier quantity (here pulse width) is quantized, then no reason to tell it's analog.
Good morning, Sir! You are at an opinion already discussed by Charles and me. I won't repeat it, you may be able to read it from last paragraph of post #27. Have a nice reading time!
Do you really wait for my permission? If you want to answer again an already answered question, you can, nobody stops you. I will not repeat myself. BTW: nobody forced you to make false generalizations about an offtopic question. It was your (and Jan's) choice.
Even the TI pdf "confess" that PWM is analog - when the marketeers has written page 1 and the technicians step in to do the rest:
Page 12: Analog supply voltage range,AVDD1,AVDD2 ................−0.3V to 4.2V
The TAS5001 is not an amplifier - some parts missing to make it play.
Lyngdorf Millenium is as a true digital amp as one can get (no PWM, digital in).
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Page 4:
AVDD1 is for oscillator
AVDD2 is for PLL
DVDD2,3 is for PWM.
Perfect job in avoiding relevance.
Tas5001+some of the many power stages form a recommended amplifier system, however a headphone attached to PWM output gives a nice sound also.
AVDD1 is for oscillator
AVDD2 is for PLL
DVDD2,3 is for PWM.
Perfect job in avoiding relevance.
Tas5001+some of the many power stages form a recommended amplifier system, however a headphone attached to PWM output gives a nice sound also.
This one does work with PWM. The TI solutions with digital modulator and the TacT amplifier use the same working principles. TI bougt this company and developed an integrated and mass-marked capable solution.
Mr. Lyngdorf is now with Steinway Lyngdorf.
Regards
Charles
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