[LINK] How can analogue be better?

stephen at melbpc.org.au stephen at melbpc.org.au
Wed Jun 3 03:03:22 EST 2009


Kim, Stephen, and Link write:

'.. the reason digital (music) sounds funny is that sampling at 40-odd
 kilohertz ruins any phase differences between the two stereo channels
 smaller than 25 microseconds..'


Sounds right, ta Stephen .. imho as well as sample-time issues there's
also frequency issues with yr stepped-wave at either CD or the new DVD
sample-rates. For example http://www.howstuffworks.com/question487.htm


But, for mine, would agree with you completely Stephen regarding vinyl 
(analogue) audio-quality over the CD (digital) for enjoyable listening


And, gasp, maybe even better than silence :) a les paul quietly played
well through an old tube-marshall, with the tone of warm creamy coffee


But whatever, we really need to go back to tubes!  Why? valves amplify
the lower and EVEN harmonics, transistors amplify higher ODD harmonics


So with a valve amplifier, you will hear the second & fourth harmonics
which fill out the sound, and, make it warm .. but with transisters :(


  http://www.vac-amps.com/sciam.html

Back in the 1930s and 1940s, tota1 harmonic distortion became a widely 
accepted parameter for describing amplifier imperfections. All amplifiers 
create spurious, ostensibly unwanted signals at frequencies that are some 
whole-number multiple of the signal being amplified. 

Thus, any second-order harmonic distortion consists of stray signals at 
exactly twice the frequency of the amplified signal. 

Because all amplifiers of that era were based on tubes with similar kinds 
of nonlinearities, they all tended to generate harmonic distortion of the 
same kind, and a single number representing the total harmonic distortion 
was a valid tool for comparing them. 

It correlated well with the subjective listening experience.

Those tube amplifiers generated mainly second-order harmonics plus small 
amounts of other, low-order EVEN harmonics (fourth, sixth and so on). 

A Second-order harmonic distortion, for that matter, is difficult for a 
human being to detect. 

Moreover, what can be heard, tends to sound pleasant.

Transistor amplifiers, in contrast, generate higher-order harmonics 
(ninth, tenth, eleventh and so on), which are much easier to hear. 

Worse, the odd-order harmonics sound bad. 

So it is possible to have a transistor amplifier whose total harmonic 
distortion - as measured by laboratory instruments - is significantly 
lower than that of a comparable tube amplifier but that nonetheless 
sounds worse. 

The debate can get quite heated - and not a little confusing - because 
the performance of an amplifier depends as much on the details of its 
circuit design as on its principal active devices (tubes or transistors). 

For example, using the feedback configuration in an amplifier circuit can 
reduce total distortion levels, but, at a price: an increased percentage 
of those easily perceived, higher-order harmonics. 

According to Hayes, transistor amplifiers need more feedback than 
amplifiers based on vacuum triodes, which he believes to be the most 
optimal audio-amplifying devices. (Hayes's favorite triode is the 300B, 
developed at Western Electric in 1935.)

Then there are the cultists, who not only prefer tube-based audio 
equipment, but, also insist that single-ended amplifiers are superior to 
push-pull units. In the latter, pairs of output tubes are arranged in a 
circuit that tends to cancel even-order distortion. 

Single-ended outputs, lacking that cancellation, can have as much as 15 
percent total harmonic distortion, mostly second order. Though readily 
detectable, the effect is not unpleasant, tending to add richness and 
fullness to the reproduced sound.


>
> Jan Whitaker wrote:
>> Ivan Trundle wrote:
>>> Mock me for being an 'audiophile' if you wish ...
>> I had a professor friend back in the 70s who would only listen to  
>> vinyl, never tape. Think cravat, pipe, and a fine port.
> Or ... think phase response.  I think the reason digital sounds  
> funny is
> that sampling at 40-odd kilohertz ruins any phase differences between
> the two stereo channels smaller than 25 microseconds.  But the human
> hearing system is sensitive to phase differences of as little as one
> microsecond, when constructing the stereo image.
>
> You can tell just by looking at a vinyl record that it contains  
> signals
> of at least 100kHz (while a CD is limited by anti-aliasing filtering  
> to
> 20kHz; MP3 may in effect be lower still).  The coloured rainbow  
> patterns
> seen on an LP's surface are caused by optical interference, indicating
> physical structures in the grooves about the same size as the  
> wavelength
> of visible light - say 500nm (I think these structures are caused by a
> high frequency bias signal applied to the master record cutting
> stylus).  My back of the envelope is that this corresponds to a
> frequency of 100kHz.

Yeah, I remember the high frequencies on vinyl albums.  We used to  
call it dust.  I had a little thing for cleaning them but it never got  
all the dust off.

A Song of Reproduction (Flanders and Swann: At the Drop of a Hat)

May we ask, could you hear that more or less all right at the top  
there? All right for quantity? Nothing we can do about the quality.  
Not until Swann's voice breaks, anyway. People make an awful lot of  
fuss, anyway about the quality of the sound they listen to. Have you  
noticed; they spend all that time trying to get the exact effect of an  
orchestra actually playing in their sitting room. Personally, I can't  
think of anything I should hate more than an orchestra actually  
playing in my sitting room. They seem to like it, and it's about these  
people who we've written this next song. I mention this in case any of  
you think the title a little close to the bone; This is a Song of  
Reproduction.

I had a little gramophone;
I'd wind it round and round,
And with a sharpish needle
It made a cheerful sound.

And then they amplified it;
It was much louder then,
And you sharpened fibre needles
To make it soft again.

Today for reproduction
I'm as eager as can be;
Count me among the faithful fans
Of High Fidelity.

High Fidelity! Hi Fi's the thing for me
With an L.P. disc and an F.M. set
And a comer reflex cabinet,
High Frequency range
And down with Auto-change!
All the highest notes, neither sharp nor flat:
The ear can't hear as high as that,
Still I ought to please any passing bat
With my High Fidelity.

Who made this circuit up for you anyway? Bought it in a shop? What a  
horrible, shoddy job they fobbed you off with. I'm surprised they let  
you have it in here! The acoustics are all wrong. Raise the ceiling  
four feet, put the fireplace from that wall to that wall, and you'll  
still only get the stereophonic effect if you sit in the bottom of  
that cupboard. What a horrible shoddy job they've fobbed you off  
with ... ! You've got your negative feedback coupled in with your push- 
pull input-output; take that across your red-head pickup to your  
tweeter, and if you're modding more than eight you're going to get wow  
on your top-try to bring that down through your rumble filter to your  
woofer. And what'll you get? Flutter on your bottom!

High Fidelity! F.F.R.R. for me!
I've an opera here that you shan't escape
On miles and miles of recording tape;
High decibel gain
Is easy to obtain;
With the tone control at a single touch
Bel Canto sounds like Double Dutch.
Then I never did care for music much
It's the High Fidelity!

MF: This is a good moment to explain that we don't normally have these  
things standing around here, but tonight they are recording this,  
stereophonically in fact, for posterity. So, wherever you're sitting  
now, it'll be where you'll be on the record. Sit up nice and straight,  
if any of you feel like rolling in the aisles or being carried out  
helpless with mirth, this is a jolly good night to do it. Do you want  
to say hello to posterity?
DS: Hello!
MF: Hello, Posterity. If we move around a bit, they'll use it for  
demonstration purposes.

>
>
> I'm not saying there are 100kHz sound waves in the LP that can get
> through the amplifier and speakers and our ears into the brain.  But
> there can be phase information at the 1 to 10 microsecond range that
> does get through -- but only in an analogue system.
>
> Cheers,
>
> Stephen Wilson.
>
>
>
>


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