Critic's Corner

Discuss a review. Provide constructive feedback. Talk to the industry.

Return to Critic's Corner


Message Sort: Post Order or Asylum Reverse Threaded

Reviewers with LP (or digital) -final

32.215.21.199

Posted on March 16, 2017 at 04:44:06
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
Chronicling the reviewers who use LP (as a primary source) was not an exact science. LP held the torch through the dark days of digital, in the 1980s and 90s. That said, it now appears the vast majority of U.S. reviewers prefer digital-CD.

These reviewers, in my opinion, got it right. With a format that always had numerous advantages, except the big one, sound. But this has changed - digital (most of it Red Book) came of age more than a decade ago, and reviewers followed accordingly.

Digital is sweeping the audio world, as predicted when the first numeric-tape recordings were made in the 1970s. I say 'sweeping' not 'swept' because this process has taken much longer than many thought. Most electronics today -inc. car audio, are analog, as are loudspeaker crossovers.

This is not unlike home cinema, which is experiencing a 30-year switch from standard-definition to HD and now, UHD. A whole new recording and playback system was needed. Audiophiles got (both) of these, but they had numerous distractions and potholes along the way.

A wobbling transport, lots of radiated noise, a poorly-designed output stage, then converters dropping from 16 bits to 1. Not all dropped this acutely, some were chopped to 5-6 bits. Now, improved 6-bit converters (like ESS 9018) or 16-20 bit R2Rs are the rage.

Then, D to A. Wait a minute, D to what ? Yup, analog, and early in the chain no less (through DAC, preamp and power amp). A solution arrived, however, with full-digital amplifiers. Here, digital signals drive a switching output stage. This type of product, out since the late 1990s, is finally getting attention - Lyngdorf TDAI, NAD M2, Technics R1 system.

DSP crossovers are catching on as well...

I remember J. Gordon Holt always breaking a story (he thought) would move us closer to live music. Embracing digital recording then later, playback, he held to his mission. Doug Sax said digital-CD "should sound better than LP", in a 1989 Stereophile interview.

Let's embrace the future -and go beyond DACs, as good as they are. If we're converting digital to analog, we're not hearing digital. How would vinyl lovers feel if we digitized LP and kept it that way through the amp ?

UHD For Audio - that's what this should be called...

 

Hide full thread outline!
    ...
Corrections, posted on March 16, 2017 at 09:05:20
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
A solution arrived, however, with full-digital amplifiers. Here, digital signals drive a loudspeaker, directly. This type of product, out since the late 1990s, is finally getting attention - Lyngdorf TDAI, NAD M2, Technics R1 system.

From the Lyngdorf site:

a digital input is processed only once in a pulse width modulator (PWM) based on the patented Equibitâ„¢ technology originally developed for the Millennium amplifier (as opposed to pulse code modulation).

From the Technics site:

This works with a newly-developed and original high-precision PWM (Pulse Width Modulation) conversion circuit,


Both quotes suggest a class D amplifier driven by a digital source. Its a bit misleading to call that a digital amplifier. Class D is not digital, but does lend itself conveniently to direct conversion.

Digital is sweeping the audio world

'Swept' is the better term, but oddly digital failed to stamp out the LP. You need not know anything about either technology to thus know that digital so far has been a failure in terms of state of the art. This is because the LP is still around, driven by market forces. Usually when a succeeding and superior technology supplants the prior art, the prior art is relegated to collectors and museums (the side valve in internal combustion gave way long ago to the overhead valve and there was no looking back).

The period of the least amount of LP reproduction was 1992-1993- IOW, a quarter of a century ago. Its been on the rise ever since.

Late last year the LP outsold digital downloads in the UK.

You are entitled to your opinion of course, but it flies in the face of the market forces which are somehow keeping the LP alive, and FWIW its not audiophiles that are doing that! Its kids- and kids have kept the LP alive for over 25 years now- its not a 'trend'. Its a simple fact that digital failed to do what audiophiles were told it would do- replace the LP.

 

RE: Corrections, posted on March 16, 2017 at 09:42:48
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
Turntables are not dead, as I found a small group of writers who still use one.

They're just hard to find (with reviewers or even readers, for that matter). With servers, streaming and DAC-integrateds exploding in popularity, it's not even close.

The amps I mentioned have no analog stages. They are fundamentally different than analog-switching amps.

 

RE: Corrections, posted on March 16, 2017 at 10:03:58
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
They are fundamentally different than analog-switching amps.

I suggest you try to build one someday and see if you still say that.

The process is the same- all that's happening is that a digital input is used instead of analog, but the process of that becoming something that drives the speaker is the same. That is why I placed the quotes from the manufacturer's websites, in an apparently vain attempt to preempt this part of the discussion.

Technics re-introduced the SL1200 in a much updated guise- the new machine is similar to the old one in appearance only- its a ground-up new and much superior design.

That really was not that hard to find.

For more easy to find turntables go to Best Buy- I saw some there last weekend.

 

RE: Corrections, posted on March 16, 2017 at 10:31:22
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
These products re-format a digital input, then send it directly to the output stage (of the amp).

We're not driving a voice-coil with digits -no, but digits are controlling the output stage of an amp. And by doing this, a huge amount of electronics are removed from the signal path.

 

RE: Corrections, posted on March 16, 2017 at 13:52:04
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
These products re-format a digital input, then send it directly to the output stage (of the amp).

We're not driving a voice-coil with digits -no, but digits are controlling the output stage of an amp. And by doing this, a huge amount of electronics are removed from the signal path.


Do you understand that the 're-format' is an analog process as well as the operation of the output section itself? If not, well: it is. This is why I suggested you try to build one sometime.

Digits are not controlling the output section of the amp! An analog process (PWM) is. This is why I quoted from the manufacturer's websites!

Pulse Width Modulation is entirely an analog process. It was first proposed in the 1940s. Once a signal has arrived in that state it is not digital. Digital is a bunch of numbers.

Class D is an analog process from start to finish. The correct term, if not class D, is 'switching'. The companies that purport to have a 'Digital amplifier' are engaging in a form of shorthand. Its marketing.

This type of amplifier and digital both have distortions that are uniquely their own. For example, digital audio has a distortion that can be called 'inharmonic distortion' and is a form of intermodulation where the intermodulation is between the signal and the scan frequency. The digital world does not like to admit this so they call it 'aliasing' but it is distortion nonetheless.

Its also very audible to the human ear. This is because aliasing artifacts tend to be high frequency in nature and so occur in the range at which our ears are most sensitive. They can't be easily detected using digital sources, but are easily heard if you record and playback using an analog sweep tone). Try it some time.

The distortions of a class D amplifier have to do with the clock frequency and the accuracy of the PCM circuitry. Switching amplifiers have some limitations not unlike digital (bandwidth being one of them); if you really want the amplifier to be low distortion, a higher scan frequency is paramount. This gets to be tricky as high speed power switching is easy enough, but the higher you go the more expensive it gets. For this reason most current class D circuits switch at a frequency that is too low (500KHz is a good minimum but 5MHz is better). The problem is avoiding phase shift in the audio passband; to do that you usually have to have bandwidth to 10x the maximum frequency to be reproduced. That puts the switching frequency higher than nearly all the class D (or so-called 'Digital Amplifiers') made.

Now the switching devices like to stay on for a while after they are turned off, so to prevent a phenomena called 'shoot-through current' which heats up the power transistors pretty fast, a circuit is installed that introduces 'dead time'; a period of time that gives the output devices of one side of the amp time to shut off before the other side turns on. The more dead time the more distortion; dead time is not needed at lower scan frequencies. So there is a bit of catch-22 situation going on there.

This is not to say that I don't see hope for the technology- Class D is clearly the rising star in amplifier technology (we've been working on it for several years now).

I have less hope for the digital audio recording industry as an attitude that its 'good enough' prevails. Your own post OP is an example. As long as that attitude is out there, analog will continue to outperform digital as the incentive to improve simply does not exist.

 

RE: Corrections, posted on March 16, 2017 at 14:25:41
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
The manufacturers don't say 'analog' - you do.

You don't make switching amps, never have.

There's nothing wrong with switching amps. Only in your head. And they are discrete output (not continuous), hence digital by definition. In the units I mention, the pulse-widths are digital, unlike all other (analog) switchers.

My intent was to give those (who don't know) an option -without raising too much attention. Now that you *caused* attention, more people are probably going to look into this, as they should.

In his review of the NAD M2, Jim Merod of PFO called it a "ridiculously happy event" and a "must". More recently, Alan Taffel of TAS said the Technics R1 went beyond his reference CH Precision gear (for digital). CH was -and still is, world class, being designed by former Goldmund engineers.

 

RE: Corrections, posted on March 16, 2017 at 15:37:51
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
Clearly you did not read my last post, please go back and re-read.

Here are the problem areas in your post:

The manufacturers don't say 'analog' - you do.

Right- that's called 'marketing'. Class D is analog. The giveaway in the quotes I lifted from their websites (again, in an apparently vain attempt to preempt this missive) is the acronym 'PWM', which I already previously explained. Google is your friend- look it up.

You don't make switching amps, never have.

Yup- but I did say we've been researching it for several years and to elucidate, that means we've built prototypes.

There's nothing wrong with switching amps. Only in your head. And they are discrete output (not continuous), hence digital by definition. In the units I mention, the pulse-widths are digital, unlike all other (analog) switchers.

There is a lot wrong with your understanding of how this all works. Again I recommend you try and build a class D amp- its not that hard and apparently will be educational. See the link below.

I outlined the technical difficulties that switching amps face. Please go back and re-read. Its in a nutshell for sure, but that does not change the fact that switchers have their own set of problems- every technology does.

As to attracting attention to this- that's a good thing so we both agree on that.

 

Please., posted on March 16, 2017 at 15:54:09
Kal Rubinson
Reviewer

Posts: 10593
Location: New York
Joined: June 5, 2002
The manufacturers don't say 'analog' - you do.
They leave out what they do not want to emphasize. Every example you have given is an amp with an analog output to feed an analog speaker.


There's nothing wrong with switching amps. Only in your head.
Not me. I like some of the new ones.

And they are discrete output (not continuous), hence digital by definition. In the units I mention, the pulse-widths are digital, unlike all other (analog) switchers.
However, when you add the output filter, the output is analog.

My intent was to give those (who don't know) an option -without raising too much attention. Now that you *caused* attention, more people are probably going to look into this, as they should.
I am afraid to say that you deserve this attention because your understanding of the technology is simplistic and misleading. It does not help your cause.

 

RE: Corrections, posted on March 16, 2017 at 15:55:11
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
These units don't work with analog signals, so your forced statement IT'S ANALOG doesn't apply.

For those who don't think this is different, I invite them to read TAS review of Technics R1. Here, Robert Harley gives a good explanation of this approach.

 

RE: Corrections, posted on March 16, 2017 at 17:52:45
RGA
Reviewer

Posts: 10192
Location: Hong Kong
Joined: August 8, 2001
It depends on the age of the reviewers to a large degree. Younger reviewers tend to not have the money for a good vinyl rig nor did they grow up with it. So it stands to reason they would be using digital.

Sound isn't the only thing at play here anyway. Turntables as stated earlier are a big pain in the arse compared to CD. Computer audio is a pain in the arse for other reasons but once set-up is convenient.

But vinyl hasn't gone anywhere - looking at HMV's Vinyl section in Hong Kong - they dedicated almost an entire floor to it. It's not just the American market.

And just look at the top end of the turntable market and see how many $50k+ vinyl rigs are out there.

Opinions as to what sounds better are just opinions. The best "sound" I have heard has been in order R2R Tape, Vinyl, CD, Bluray, SACD, and in last place Computer Audio.

I will head to the California Audio Show in July and perhaps someone will be able to convince me to change the order. But here in Hong Kong in a Nottingham turntable demonstration against a fairly pricey computer audio DAC the turntable was very enjoyable - I had to shut Eva Cassidy off on the CA player it was so appalling.

And yes I have a Computer Audio Player - the Line Magnetic 502CA which uses a Sabre chip. In tube mode it is nice. SS it is virtually unlistenable which mirrors other SS computer audio.

 

Link? (nt), posted on March 16, 2017 at 21:39:37
mkuller
Audiophile

Posts: 35174
Location: SF Bay Area
Joined: April 22, 2003
Contributor
  Since:
December 28, 2003
(nt)

 

RE: Link? (nt), posted on March 17, 2017 at 06:29:15
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
These type of products amplify in the digital domain, not analog. "Digital amp" would be the correct term.

And the output filter is one part, not a stage.

Under 'digital amplifiers':

 

Most likely you still won't get it, but..., posted on March 17, 2017 at 06:53:31
E-Stat
Audiophile

Posts: 24521
Joined: May 12, 2000
Contributor
  Since:
April 5, 2002
This from your linked review:

"however, they accept digital rather than analog input signals. These "digital" amplifiers take in the pulse-code modulation (PCM) signal from a music server or other source and convert those audio data to a pulse-width modulated signal. This PWM signal then drives the output transistors, just as in a Class D amplifier. "

While its input may be digital, its output is necessarily the same as an analog switcher.

 

RE: Most likely you still won't get it, but..., posted on March 17, 2017 at 07:17:49
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
It might be -but the point is that the amp removes all analog stages. Inc. D to A converter, current to voltage, DAC output-ramp, etc.

 

I was correct, posted on March 17, 2017 at 07:22:06
E-Stat
Audiophile

Posts: 24521
Joined: May 12, 2000
Contributor
  Since:
April 5, 2002
t might be -but the point is that the amp removes all analog stages.

Except of course for the output stage driving the speakers with an analog signal. :)

 

RE: you still won't get it..., posted on March 17, 2017 at 08:41:07
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
-but the point is that the amp removes all analog stages.

This statement is false.

PWM (pulse width modulation) and PCM (pulse code modulation) are both analog processes. There is no such thing as a true digital amplifier.

 

RE: Corrections, posted on March 17, 2017 at 08:53:21
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
These units don't work with analog signals, so your forced statement IT'S ANALOG doesn't apply.

This statement is outright false.

In order for a digital bit-stream to drive an amplifier, it gets converted into a series of pulses, which works out nicely for a class D amp, since that's what the converters in a normal class D amp do as well. So its a simple matter to marry a DAC and a class D amp together.

But that process is entirely analog. If it were not, there would not be a DAC in the circuit. There is no such thing as a pure digital amplifier.

Any hardware technician can tell you that the process that allows a computer or any digital product to work is also an analog process. The analog signals are merely interpreted as being digital ('on' or 'off'). But anyone that works with digital chips knows that they have a margin, for example a 5Volt digital chip is designed to interpret anything from about 4.2 volts to 5 volts and an 'on' signal. So its even worse than you imagined!

The reason there are things like 'errors' and the need for parity bits and the like is the simple fact that a digital signal can be eroded by the analog process in which it resides; degradation of magnetic or optial media, noise on transmission lines between ICs and so on. Its **all** analog. That's the world in which we live.

The situation here is that you like your gear and I'm not attacking it. What I am attacking is your argument which is heavily flawed, as others here are confirming.

 

RE: you still won't get it..., posted on March 17, 2017 at 10:57:40
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
I've never heard anyone say PCM is analog.

As for the unit, even Robert Harley says it: *digital* amp.

 

RE: Corrections, posted on March 17, 2017 at 10:59:39
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
You don't work with digital circuits, so your comments are ignored.

As to the unit in question, there is NO DAC in the circuit.

 

RE: you still won't get it..., posted on March 17, 2017 at 11:27:44
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
PCM is for the encoding of analog signals to digital.

 

That's really funny, posted on March 17, 2017 at 11:28:42
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
No DAC- no conversion. Therefore does not drive speakers either.

 

RE: you still won't get it..., posted on March 17, 2017 at 11:34:25
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
But we're not encoding. We're only dealing with digital signals.

 

Which means:, posted on March 17, 2017 at 11:48:52
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
You won't be doing PCM. Instead, you'll be using PWM, which is an analog process. It can be adapted very nicely for use with digital systems.

The specific forms of PWM used in the amps to which you referred is either Delta or Delta Sigma.

Read the Wiki article at the link.

Notice things like 'waveform', 'integration' and so on- all analog thingys.

The fact is the world is analog and true digital does not exist in it. That is why IBM developed the parity bit.

 

RE: Which means:, posted on March 17, 2017 at 13:54:00
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
Your links don't prove anything, at least in this discussion.

Harley said digital amp and the signals are amplified in the digital domain.

Digital is everywhere inc cable-TV systems and satellites. For audio, DSP crossovers could be placed before a digital amp. (1) part in the output stage sends the signal to the speakers.

This technically is analog, but it's far different than the slow-speed circuits and gain stages we're all accustomed to.

 

Wow., posted on March 17, 2017 at 14:19:49
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
So, faced with the rather obvious facts, you prefer to go with one person, who, if you were to ask him, would confirm everything I said?

Point him at this thread and see what he says!

 

RE: Wow., posted on March 17, 2017 at 17:08:53
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
Don't know what 'point him' means.

And it's more than one person -it's any co. making this type of product -inc. Classe. Plus AES papers explaining all this (which can't be linked).

 

:), posted on March 17, 2017 at 18:37:04
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
That's because said papers don't exist :)

 

RE: :), posted on March 17, 2017 at 19:19:11
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
They do, but the products are what really count. Growing by the year.

 

Start with the dictionary definition of "digital", posted on March 18, 2017 at 09:59:54
Dave_K
Audiophile

Posts: 1057
Joined: September 30, 2014
Contributor
  Since:
December 0, 0000
I looked it up in a few different dictionaries. The consensus is that in the context of signals and data, "digital" means representing a quantity as a series of numbers, presumably finite, usually but not necessarily binary numbers.

So in the case of pulse width modulation, if the pulse width is constrained to be one of a finite number of possible values, then it would be fair to call it a digital signal.

Once you low pass filter it after amplification by a high power switching output stage, the output at the binding posts is analog. Kind of like a R2R ladder DAC, which is why some people call this type of Class D amp a "power DAC".

J.Phelan has a point in that the amplifiers he mentioned are different from other Class D amplifiers having digital inputs (e.g. Tripath) which have a more conventional DAC followed by PWM formed in the analog domain.

 

RE: Start with the dictionary definition of "digital", posted on March 18, 2017 at 12:58:04
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
And they're not easy to make. Noise-shaping is required, but I wonder if the Technics R1 system has a clock frequency high enough to avoid it.

The output stage has 1-part -analog. But this too looks different -it's now high-speed. Compared to the typical slow, losing-its-shape analog waveform.


 

RE: Reviewers with LP (or digital) -final, posted on March 18, 2017 at 15:37:13
morricab
Reviewer

Posts: 8450
Location: switzerland
Joined: April 1, 2005
I would not agree that digital was in th dark days in the 90s. In fact there were some dacs and chips in use(multibit) that go toe to toe with the best today and ARE used in the best today (think AD1865, for example). BB PCM63PK are still revered today as well because they sound good. Couple a good multibit with a good team be output stage and best of will have a more analog sounding digital

 

RE: Reviewers with LP (or digital) -final, posted on March 18, 2017 at 16:24:04
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
I believe this, but most audiophiles were complaining quite vociferously in the 1990s.

And we have seen considerable drop in clock/phase noise and much improved output stage. But it's hard to isolate how much better (one area) of design is.

The return of R2Rs proves your point -it's what DACs used back then.

 

RE: Start with the dictionary definition of "digital", posted on March 20, 2017 at 09:37:31
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
The Technics is one of the few that has a clock speed approaching what is needed and so far looks like one of the better class D amps out there.

 

RE: Start with the dictionary definition of "digital", posted on March 20, 2017 at 09:49:51
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
Clearly the line between what is an analog process is what is considered 'not' is a bit dubious. Your point is well taken, and not germane to where this thread started, although once that got debunked it drifted pretty wildly afterwards...

I look at things from an engineering standpoint as that is my training. And having built class D amps, know that they are an entirely analog process. As I mentioned earlier on in this train wreck, class D lends itself nicely to hybridization with a DAC for a more direct-conversion process, but its wholly inaccurate to say that such an amplifier it truly digital when an obviously analog process is employed. The guy that started this was insisting that class D was digital all the way to the output, which really isn't true at all- otherwise dead time circuits and other aspects of class D operation simply would not be needed.

 

RE: Start with the dictionary definition of "digital", posted on March 20, 2017 at 10:01:15
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
You never built a class D amp, therefore your comments (should be) ignored.

Look at the Harley piece. A sample-rate converter is used -that is NOT analog. These are digital all-the-way, as far as the amp is concerned.

 

you would be incorrect about that, posted on March 20, 2017 at 10:47:25
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
Clearly you've not read my prior posts...

I have in fact built class D amps. We've been developing our own for some time and have a patent in the works. I also linked a simple class D amp for you to look at, easy to build, and had you read the simple article (with lots of photos) at that link, you would also know that all class D amps are an analog process.

From the Wikipedia page on Class D amps:

Terminology
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.

emphasis added; after that follows why class D is in fact not digital.

 

RE: you would be incorrect about that, posted on March 20, 2017 at 11:38:52
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
Your company never sold a class D amp.

And you keep linking *outdated* information.

Besides Harley, here's another. Note the statements "digital input fed directly to the output stage", "keeps everything in the digital domain".

 

Wow. Just wow., posted on March 20, 2017 at 12:46:29
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
So how it works for you is that facts go out of date. Would it help if that Wiki page got refreshed recently??

So Norman Crowhurst (was writing 60 years ago) can be ignored? How about Shannon- I suppose he's pretty out of date too huh? and that Nyquist dude- he's so old he's dead? Sheesh!

The Wiki page is factual. If class D had somehow become true digital in the meantime, it would have been an article worth the front cover of every audio magazine in the world.

But apparently you only believe people who listen to stuff for magazines as the only possible experts in the world.

How about people that actually have an engineering degree or work on class D amps or anything like that?

Do you think that because we've only sold tube amps so far, that tube amps are somehow the only thing I know??

Is there any possibility that you simply don't me as a person? Any rational person would know the answer right away- you don't know me, don't know my qualifications, don't know what my job entails, etc. You just have made-up stories.

You've been taken in by advertising; hype, hook, line and sinker.

 

RE: Wow. Just wow., posted on March 20, 2017 at 14:23:18
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
You have no proof you built a class D amp. I could say *I* built one !!

Now, it's not "marketing", it's "magazines". John Atkinson and Robert Harley were "taken" by advertising. I don't think so.

Digital amps are the future !!

 

RE: Wow. Just wow., posted on March 20, 2017 at 14:56:16
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
I see.

Don't confuse the situation with facts huh?

I'm sure it does not matter how many awards I've gotten (about 35 or so) or how long I've been in business (over 40 years) or anything like that. You'll go with someone that writes instead of someone in the industry that actually makes amps for a living. Because you have to be right.

It'll be interesting when someone actually makes a digital amp.

From the link below:
Footnote 1: The D in class-D does not stand for digital, as some commentators have suggested. Rather, D was just the next available letter in the alphabet when amplifier circuit topologies were being classified. A class-D amplifier can be either digital or analog in operating principle.

The author, John Aitkinson, happens to be misleading in this comment, as there is no such thing as a digital amplifier. If you change the last sentence above to read " A Class-D amplifier is analog in operating principle" then the entire paragraph would be correct. How about I see if we can get JA to weigh in on this?

 

RE: Wow. Just wow., posted on March 20, 2017 at 17:24:37
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
Mmmm...John Atkinson 'misleading', I hope he sees this.

You're the only person who says "no such thing as a digital amp". There is.

Now a schematic, which eschews analog stages. No wait, this is phony too !!

 

That's a good link, posted on March 21, 2017 at 08:38:29
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
I've spent some time on that site in the past as it often comes up in Google searches. I would direct you to other portions of the site which refute your claims but since you've not read a lot of that sort of thing in the past there is no expectation that you would do so now.

JA would be welcome in the discussion. I'm sure he can clarify.

 

RE: That's a good link, posted on March 21, 2017 at 15:58:53
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
Can't refute the page I linked.

Atkinson and Harley have enough credibility, they don't have to 'clarify'.

By causing this thread to 'spiral', you pulled more attention to it. Thanks to you, they'll now be a buzz on (true) digital amps...


 

RE: That's a good link, posted on March 22, 2017 at 10:06:59
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
If you're claiming that the amp at that thread is a digital amp, well it uses analog process to do its job. Quite literally there is no way it can't.

This is true of any amplifier that can drive a loudspeaker.

If a reviewer that has never built an amplifier before wants to contest that, all that happens is he's wrong. In JA's case, I'm pretty sure he was using shorthand with his use of 'digital amplifier' and I'm also sure he would be happy to clarify that for you.



 

A pretty good description of class D and why its not actually digital., posted on March 22, 2017 at 10:56:17
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
From the link below (some images are missing- see the link):

Class D

Often erroneously referred to as "digital amplification", Class D amplifiers represent the zenith of amplifier efficiency, with rates in excess of 90% being achieved in the real world. First things first: why is it referred to Class D if "digital amplification" is a misnomer? It was simply the next letter in the alphabet, with Class C being utilized in non-audio applications. More importantly, how is 90%+ efficiency possible? While all the amplifier classes previously mentioned have one or more output devices active all the time, even when the amplifier is effectively idle, Class D amplifiers rapidly switch the output devices between the off and on state; as an example, Class T designs, which are an implementation of Class D designed by Tripath as opposed to a formal class, utilize switching rates on the order of 50MHz. The output devices are typically controlled by pulse width modulation: square waves of varying widths are produced by a modulator, which represents the analog signal to be reproduced. By tightly controlling the output devices in this way, efficiency of 100% is theoretically possible (although obviously not achievable in the real world).

Class D TopologyIQ M300 Amplifier

Example of a full bridge Class D circuit (left; sourced from sound.westhost.com), and the IQ M300 Class D amplifier, a pint sized 300W wonder (right).

Delving deeper into the world of Class D you'll also find mention of analog and digital controlled amplifiers. Analog-controlled Class D amplifiers have an analog input signal and an analog control system, usually with some degree of feedback error correction present. On the other hand, digitally controlled Class D amplifiers utilize digitally generated control that switches a power stage with no error control (those that do have an error control can be shown to be topologically equivalent to an analog-controlled class D with a DAC in front). Overall, it's worth noting that analog controlled Class D tends to have a performance advantage over its digital counterpart, as they generally offer lower output impedance and an improved distortion profile.

Next, there is the (not so) small matter of the output filter: this is generally an L-C circuit (inductor & capacitor) placed between the amplifier and the speakers in order to mitigate the noise associated with Class D operation. The filter is of considerable importance: shoddy design can compromise efficiency, reliability, and audio quality. In addition, feedback after the output filter has benefits. While designs that do not utilize feedback at this stage can have their response tuned to a particular impedance, when such amplifiers are presented with a complex load (i.e. a real world loudspeaker as opposed to a resistor), frequency response can vary considerably depending on the loudspeaker load it sees. Feedback stabilizes this issue, ensuring a smooth response into complex loads.

Ultimately, the complexity of Class D has its rewards: efficiency, and as a good consequence, less weight. As relatively little energy is wasted as heat, much less heat sinking is required. Ratcheting that up a notch, many Class D amplifiers are used in conjunction with switch mode power supplies (SMPS). Like the output stage, the power supply itself can be rapidly switched on and off to regulate voltage, leading to further gains in efficiency and the ability to shed weight relatively to traditional analog / linear power supplies. Taken together, it's possible for even high powered Class D amplifiers to weigh only a few pounds. The disadvantage of SMPS power supplies over traditional linear supplies is the former typically don't have much dynamic headroom. Our limited testing of Class D amps with linear supplies vs SMPS supplies have shown this to be true where two comparably rated power amps both delivered rated power, but the one with the linear supply was able to produce higher dynamic power levels. Still SMPS designs are becoming more commonplace now, and you can expect to see more high powered, next generation Class D amplifiers employing them.

 

RE: A pretty good description of class D and why its not actually digital., posted on March 22, 2017 at 14:29:38
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
This piece offers more proof that there are 'digitally-controlled amplifiers', which the link states.

 

RE: That's a good link, posted on March 22, 2017 at 14:31:34
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
Did John tell you he would clarify ? These are digital amps, as the schematic shows...

 

Ah. So we're in agreement here., posted on March 22, 2017 at 15:15:40
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
IOW, not a digital amp, but a digitally controlled amp. No worries there.

 

RE: That's a good link, posted on March 22, 2017 at 15:16:38
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
The schematic shows nothing of the sort. I have to assume something like that is not in your wheelhouse.

 

RE: Ah. So we're in agreement here., posted on March 22, 2017 at 15:29:42
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
But when referring to digital-controlled, it doesn't say 'analog'.

 

That's right!, posted on March 23, 2017 at 09:32:39
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
But as any technician can tell you, there's a huge difference between being 'all digital' and 'digitally-controlled'!

I play in a band and have a variety of synthesizers. Most are entirely analog but a few are digitally-controlled. However despite the digital control they are still considered analog synths because the oscillators and filters and such are still analog despite the digital control.

Much the same is going on with class D amps. As I've mentioned several times, the switching means that class D uses lends itself quite well to use with a digital input (with no analog input). But to get the output transistors to switch properly from the bit stream of the digital source there is an analog conversion system employed. Further, the usual considerations of power supply voltage, the risetime of the output devices and how long it takes for them to shut off, plus the stripping of the switching frequency from the signal at the output of the amp are all concerns in the analog domain.

Its easy to understand how a person might think that such an amplifier is a 'digital amp' but that moniker is erroneous as that is not how the amp works.

I think your confusion here comes from the fact that analog processes cover a lot more ground than just a simple audio signal! For example if there is a reflection on a transmission line you have to use analog techniques to tame it- if you don't, the digital system in which the transmission line (an analog device in itself BTW) resides will generate errors.

 

RE: That's right!, posted on March 23, 2017 at 14:26:06
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
There is no analog stage - as John Atkinson, Robert Harley and the schematics show.

 

You don't know what 'analog' means, apparently, posted on March 24, 2017 at 09:24:57
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
Its a lot more than just an audio signal...

Are you aware that the process of extracting data from a CD or magnetic disk drive is also an analog process?

 

RE: You don't know what 'analog' means, apparently, posted on March 24, 2017 at 13:31:56
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
We're not talking about those things. This is all-new technology, invented by the Danish (TacT Millennium -1998). Robert Greene of TAS reviewed it -twice.

 

That's pretty funny., posted on March 24, 2017 at 14:04:53
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
You really don't have any idea do you!

 

RE: That's pretty funny., posted on March 24, 2017 at 15:20:30
J. Phelan
Audiophile

Posts: 579
Joined: May 12, 2009
I don't need an idea. These products are real-world, accept or not...

 

RE: That's pretty funny., posted on March 27, 2017 at 09:40:22
Ralph
Manufacturer

Posts: 3307
Location: Minnesota
Joined: April 24, 2002
Contributor
  Since:
April 1, 2002
You don't to be confused with the facts huh?

Alright- I'm not going to argue with you. You don't want to know and apparently that can't be helped by your own admission.

 

Page processed in 0.034 seconds.