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Andre Jute
Guest
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 Posted:
Sat Sep 24, 2005 4:43 am Post subject:
What is digital audio? The Neddy Report. |
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In the current thread Report - 2005 London HiFi Show, Andy Evans talks
about digital audio as the wave of the future, and Patrick too
mentioned it twice already.
Can someone please explain to me what digital audio is? I haven't read
the trade magazines in a decade, so I am right out of it; please start
from scratch and don't deprive me of any riches. Is it audio made by
noughts and ones; does the entire chain to and including the speaker
become digital? I thought part of even the most rabid tubie's audio
chain was digital already, in that a CD player is a digital on-off
device as far as the laser that reads it is concerned.
TIA.
Andre Jute
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Phil Allison
Guest
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| Posted:
Sat Sep 24, 2005 10:00 am Post subject:
Re: What is digital audio? The Neddy Report. |
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"Andre Jute"
| Quote: |
In the current thread Report - 2005 London HiFi Show, Andy Evans talks
about digital audio as the wave of the future,
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** I do not see the phrase "digital audio" in his report at all.
| Quote: | Can someone please explain to me what digital audio is?
|
** PCM or similar (eg MP3 ) coded data that represents an audio signal.
| Quote: | I haven't read
the trade magazines in a decade, so I am right out of it; please start
from scratch and don't deprive me of any riches. Is it audio made by
noughts and ones; does the entire chain to and including the speaker
become digital? I thought part of even the most rabid tubie's audio
chain was digital already, in that a CD player is a digital on-off
device as far as the laser that reads it is concerned.
|
** Andy did use the phrase "digital amp" - which is a popular misnomer for
class D or PWM.
Some makers call an amp "digital" if it will accept a PCM data stream for
its input - while others us the title to describe PWM amps that take PCM
as input.
.......... Phil |
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Andre Jute
Guest
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| Posted:
Sat Sep 24, 2005 11:07 am Post subject:
Re: What is digital audio? The Neddy Report. |
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Phil Allison wrote:
| Quote: | "Andre Jute"
In the current thread Report - 2005 London HiFi Show, Andy Evans talks
about digital audio as the wave of the future,
** I do not see the phrase "digital audio" in his report at all.
Can someone please explain to me what digital audio is?
** PCM or similar (eg MP3 ) coded data that represents an audio signal.
I haven't read
the trade magazines in a decade, so I am right out of it; please start
from scratch and don't deprive me of any riches. Is it audio made by
noughts and ones; does the entire chain to and including the speaker
become digital? I thought part of even the most rabid tubie's audio
chain was digital already, in that a CD player is a digital on-off
device as far as the laser that reads it is concerned.
** Andy did use the phrase "digital amp" - which is a popular misnomer for
class D or PWM.
Some makers call an amp "digital" if it will accept a PCM data stream for
its input - while others us the title to describe PWM amps that take PCM
as input.
......... Phil
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Now I am even more confused, Phil. How can a Class D amp be a hi-fi
amp? The bloody thing would need so much error correction and
equalization, it would become monstrous to design. What could possibly
be the advantage?
Andre Jute |
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Phil Allison
Guest
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| Posted:
Sat Sep 24, 2005 11:52 am Post subject:
Re: What is digital audio? The Neddy Report. |
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"Andre Jute"
Phil Allison = replying to a completely new question:
| Quote: |
Now I am even more confused, Phil. How can a Class D amp be a hi-fi
amp?
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** Examples already exist.
Look up the Crown K series power amps - been on the market for 10 years at
least.
THD is around 0.03 % at full power.
| Quote: | The bloody thing would need so much error correction and
equalization, it would become monstrous to design. What could possibly
be the advantage?
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** Up to 95% conversion efficiency.
Virtually no heat generation.
Ideal for powerful, 6 channel HT amps.
........... Phil |
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Andre Jute
Guest
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| Posted:
Sat Sep 24, 2005 12:00 pm Post subject:
Re: What is digital audio? The Neddy Report. |
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Thanks for your patience, Phil. I got it now. Home theatre... -- Andre
Jute
Andre Jute wrote:
| Quote: | Phil Allison wrote:
"Andre Jute"
In the current thread Report - 2005 London HiFi Show, Andy Evans talks
about digital audio as the wave of the future,
** I do not see the phrase "digital audio" in his report at all.
Can someone please explain to me what digital audio is?
** PCM or similar (eg MP3 ) coded data that represents an audio signal.
I haven't read
the trade magazines in a decade, so I am right out of it; please start
from scratch and don't deprive me of any riches. Is it audio made by
noughts and ones; does the entire chain to and including the speaker
become digital? I thought part of even the most rabid tubie's audio
chain was digital already, in that a CD player is a digital on-off
device as far as the laser that reads it is concerned.
** Andy did use the phrase "digital amp" - which is a popular misnomer for
class D or PWM.
Some makers call an amp "digital" if it will accept a PCM data stream for
its input - while others us the title to describe PWM amps that take PCM
as input.
......... Phil
Now I am even more confused, Phil. How can a Class D amp be a hi-fi
amp? The bloody thing would need so much error correction and
equalization, it would become monstrous to design. What could possibly
be the advantage?
Andre Jute |
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Ian Iveson
Guest
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| Posted:
Sat Sep 24, 2005 12:11 pm Post subject:
Re: What is digital audio? The Neddy Report. |
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Andre Jute wrote
| Quote: | Can someone please explain to me what digital audio is? I haven't
read
the trade magazines in a decade, so I am right out of it; please
start
from scratch and don't deprive me of any riches. Is it audio made
by
noughts and ones; does the entire chain to and including the
speaker
become digital? I thought part of even the most rabid tubie's
audio
chain was digital already, in that a CD player is a digital on-off
device as far as the laser that reads it is concerned.
|
"Digital" became confused with "binary". Originally I assume it had
something to do with digits, like with a digital watch. It is useful
in this context to use the wider definition of "encoded in discrete
steps". Binary is then just the most simple form of digital. Most
digital audio is not binary.
However, by this definition, the output of a DAC is digital.
These days in audio, "digital" seems to mean "switched". The link
with binary is that "switched" means "on or off" which is associated
with "1 and 0". But it isn't binary in the computing sense, as in
"binary number", because the code is carried not by sequence, but by
timing. For example, PWM uses the width of switched pulses to encode
the information. That information can be analogue, in which the
pulses can be of any width, or digital, in which the pulse width
varies in discrete steps.
Crudely, you can see a "digital amplifier" as a switch-mode power
supply controlled by a coded audio signal. It may accept an audio
signal and encode it, or it may accept one code and convert to
another. In any event, its output is switched, so it must be coded.
There are looser definitions. The shops are full of "digital"
speakers and headphones that have nothing digital about them.
However, the boundaries between traditional boxes are shifting. I
reckon if a speaker is loaded with digital amplifiers, filters,
noise-cancellation and room-optimising processors et al, it gets to
be called a digital speaker.
cheers, Ian |
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Andre Jute
Guest
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| Posted:
Sat Sep 24, 2005 12:30 pm Post subject:
Re: What is digital audio? The Neddy Report. |
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Thanks, Ian. Looks like I confused myself by a careless reading of
Andy's show report, as Phil has already hinted.
| Quote: | Crudely, you can see a "digital amplifier" as a switch-mode power
supply controlled by a coded audio signal.
That's pretty bloody crude, not your explanation but the device. The |
Germans have a word for this sort of thinking: schlimmbesserung. It
means an improvement that makes things worse.
Andre Jute
Ian Iveson wrote:
| Quote: | Andre Jute wrote
Can someone please explain to me what digital audio is? I haven't
read
the trade magazines in a decade, so I am right out of it; please
start
from scratch and don't deprive me of any riches. Is it audio made
by
noughts and ones; does the entire chain to and including the
speaker
become digital? I thought part of even the most rabid tubie's
audio
chain was digital already, in that a CD player is a digital on-off
device as far as the laser that reads it is concerned.
"Digital" became confused with "binary". Originally I assume it had
something to do with digits, like with a digital watch. It is useful
in this context to use the wider definition of "encoded in discrete
steps". Binary is then just the most simple form of digital. Most
digital audio is not binary.
However, by this definition, the output of a DAC is digital.
These days in audio, "digital" seems to mean "switched". The link
with binary is that "switched" means "on or off" which is associated
with "1 and 0". But it isn't binary in the computing sense, as in
"binary number", because the code is carried not by sequence, but by
timing. For example, PWM uses the width of switched pulses to encode
the information. That information can be analogue, in which the
pulses can be of any width, or digital, in which the pulse width
varies in discrete steps.
Crudely, you can see a "digital amplifier" as a switch-mode power
supply controlled by a coded audio signal. It may accept an audio
signal and encode it, or it may accept one code and convert to
another. In any event, its output is switched, so it must be coded.
There are looser definitions. The shops are full of "digital"
speakers and headphones that have nothing digital about them.
However, the boundaries between traditional boxes are shifting. I
reckon if a speaker is loaded with digital amplifiers, filters,
noise-cancellation and room-optimising processors et al, it gets to
be called a digital speaker.
cheers, Ian |
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Patrick Turner
Guest
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| Posted:
Sat Sep 24, 2005 10:31 pm Post subject:
Re: What is digital audio? The Neddy Report. |
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Andre Jute wrote:
| Quote: | Thanks for your patience, Phil. I got it now. Home theatre... -- Andre
Jute
|
Perhaps you could go to
http://www.ciaudio.com/
Click on the D.100 monoblocks.
These are cubic in shape with a side dimension of 150mm.
The main weight is the toroidal power tranny.
When you first look inside these you have to ask where the
heatsinks are and where is all the circuitry.
The case is all it needs for the HS and the circuitry is a
a tiny 50mm square board of fearsomely complex
stuff but in a tiny package, which is routine for all electronics now
which are assembled by robots, since all the parts are too small
for clumsy dangerous dirty humans to be trusted with.
Once they set up the production lines for such items the cost
of a board for such amps might be 50c.
They just churn them out, at thousands a day.....
I had to service a pair one of which was supposed to have noise problems but
which i found to be faultless when i tried it in my system, so it must have been a
source
or cable problem.
The output mosfets or transistors were two TO220 packages on a T section bolted to
the
rear AL case plate.
I didn't take a good look at the output wave form but if you have
a wave that wave consists of a HF wave of say 500kHz which is a square wave,
and you have an appropriate output filter, and you vary the width
of duration of each square wave, ie, you have a varying pulse width
vs the signal level, then the output voltage into the load is linear with
pulse width.
Its been known for about 60 years, and pulse with FM demodulation
was attempted using tubes, to give low thd signal detection.
But doing anything digital or with PWM using tubes is totally
impractical because of the cost of the complexity.
But using chips with perhaps thousands of components and
hundreds of integrated functions is no trouble nowdays,
hence the rather simple looking boards of mobile phones,
TV sets, and PCs, ( until you look with a magnifying glass,
or you see the schematic, which will fill a whole table with
almost incomprehensible complexity..).
But I digress.
Maybe you sould look at the principles of the various means by which class D is
implemented.
I am not sure which sites there are which explain this, but surely a search will
inform you more than i can.
Basically, the output devices are either turned on fully, or not at all,
to the voltage x current figure is always a low product, so the devices
don't dissipate the power like in a class B, AB or A SS amp.
95% of the power input to the amp at full power is dissipated in the load.
I had a good listen to the CiAudio amps and
I thought them to be quite equal to many good class B SS amps which have
dominated amp design to this time for the last 40 years.
So since the class D amp can be even "sweet" sounding to at least some ppl,
including the owner of these two amps i saw myself, it would seem that
all other amps could only be like dinosoars waiting around to die out
now that the class D asteroid has hit their planet.
That process was not an overnight event, but I just cannot
see the existing ediface of class B SS amps escaping the
demolition by the lighter, and cheaper to make D amps.
So I expect loyalty to brands of large class B amps to rapidly fade
and marketing will hasten all this as existing amp makers switch to D
over the next 10 years.
Then the quality will slide due to economy considerations,
and the status quo will hover around a lowest common denominator.
But the cost in $$$ per watt should plummet to maybe 50% or less than what it is
now.
Maybe the chinese will lead the charge before Krell and Mark Levinson wake up.
But while we see amp building going all lean, mean, and digital,
there will be those of us who will remain oblivious to all this
"progress", and we will stick with our tubes and mainly class A sound amps.
Digital amps make sense for HT because the cost of a 5.1 amp
ca be quite cheap to make.
Usually such amps, or HT receivers are a nightmare of complexity
inside because of the disease of "featuritis" that engineers and consumers both
seem to suffer from.
HT sound is often pretty damn awful since so much processing of movie tracks occurs,
and so its a complete waste of glassware to use tubes for a HT set up.
People stop objecting to awful sound if there is a good picture to watch.
( Except me of course; I walk out of movies at my film club if the audio
is stuffed; I take no shite. ).
But at my film club its a rather good system they have there, a full surround system
for a proper theatre, and a 12 metre wide screen.
The venue is a university lecture theatre though, without drapes, but still its not
too reverberant.
Class D amps would surely sound as good as the all analog
amp system they have in their now.
If I ever find that a HT screen will be cheap and affordable enough,
and i get tired of the 8 minute drive down to the uni film club
or my city's commercial theatres, then all i will need
is a decent stereo 2 channel sound system.
Movies do not need to have surround imho.
Its the story, the acting, the emotional connection to
characters that make movies my main entertainment,
and something is seriously wrong if the effect has to depend on the sound system
complexities of multi channel sound.
So I will probably settle for a humble 20 watt per channel tube amp
for any future audio system for home movies.
Patrick Turner.
| Quote: |
Andre Jute wrote:
Phil Allison wrote:
"Andre Jute"
In the current thread Report - 2005 London HiFi Show, Andy Evans talks
about digital audio as the wave of the future,
** I do not see the phrase "digital audio" in his report at all.
Can someone please explain to me what digital audio is?
** PCM or similar (eg MP3 ) coded data that represents an audio signal.
I haven't read
the trade magazines in a decade, so I am right out of it; please start
from scratch and don't deprive me of any riches. Is it audio made by
noughts and ones; does the entire chain to and including the speaker
become digital? I thought part of even the most rabid tubie's audio
chain was digital already, in that a CD player is a digital on-off
device as far as the laser that reads it is concerned.
** Andy did use the phrase "digital amp" - which is a popular misnomer for
class D or PWM.
Some makers call an amp "digital" if it will accept a PCM data stream for
its input - while others us the title to describe PWM amps that take PCM
as input.
......... Phil
Now I am even more confused, Phil. How can a Class D amp be a hi-fi
amp? The bloody thing would need so much error correction and
equalization, it would become monstrous to design. What could possibly
be the advantage?
Andre Jute |
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Phil Allison
Guest
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| Posted:
Sun Sep 25, 2005 4:43 am Post subject:
Re: What is digital audio? The Neddy Report. |
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** Verrrrry suspicious.
They spec everything EXCEPT the THD figures.
........... Phil |
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Patrick Turner
Guest
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| Posted:
Sun Sep 25, 2005 7:29 pm Post subject:
Re: What is digital audio? The Neddy Report. |
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Phil Allison wrote:
| Quote: |
Perhaps you could go to
http://www.ciaudio.com/
Click on the D.100 monoblocks.
** Verrrrry suspicious.
They spec everything EXCEPT the THD figures.
.......... Phil
|
Perhaps they don't want to frighten the horses.
Probably they are no worse than many other
fairly high thd amps, but then much is said about
the significance of the spectral content of IMD and THD produced by any
amp.
An SET class A amp sounds ok with 1% of 2H with everything else
down 25dB below that, but would sound not so good
with a mix of 3,4,5,6,7,8,9 h in significant quantities which would then
result
in a more complex set of IMD products.
I am no technical expert about CiAudio, but to my ears they sounded very
much like any other reasonable SS amp.
Patrick Turner. |
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