Feedback in audio esp wrt op-amps.

[Eeyore]

Most instruments produce overtones as well as -- or instead of --
harmonics. They don't fall directly on multiples of the fundamental no
matter what tuning is used.

The technical definition of an overtone is no different from a harmonic other than
its number.

1st overtone = 2nd harmonic etc.

That itself has no relation to the production of 'harmonics' that are not integer
multiples of the fundamental. I'd like to see some more evidence of this alleged
behaviour too.

Graham

 

[Paul Stamler]

In an "Electronics World" article about the new JBL solid-state amp with a
"T" output stage. The author explicitly stated the principle -- get the
circuit as linear and wideband as possible before applying feedback.

The principle wasn't new, though; Norman Crowhurst was talking about it in
the 1950s.

That was an interesting design; I remember it as sounding good, but it's
been a really long time since I heard one.

Peace,
Paul

 

[Peter Larsen]

Masking is not *that* frequency-sensitive.

This is not about masking, it is about pitch, and pitch is acutely
heard.


Kind regards

Peter Larsen

 

[Peter Larsen]

But who's still using those old tunings ?

There are people here knowing vastly more about music than I do, but all
instruments that allow intonation are in my understanding likely to use
or at least approximate those scales unless playing with a tempered
instrument. After all, that is what the intonation advantage is about.

I've heard the difference it makes to how the music sounds btw (at college 30
yrs ago) and it's quite remarkable.

Listen to a good string quartet Graham, the purity of tone they offer
can be astounding. Or a solo violin playing solo, add a piano and the
player will intonate differently, and the very same violin now sound
grungy because it has to follow the piano.

Graham

Kind regards

Peter Larsen

 

[Mr.T]

I understand what you said, but it isn't really relevant except in the
case of the equalizer mentioned by another person in this thread, or if
you want to handwave about the number of individual op-amps in all the
channel strips on that SSL.

Not me, but isn't that what you are doing?

Pop the cover on an SSL 4000 and count the number of individual gain stages
from the front to the back, then into the tape mchine and back again. There
are lots.

Sure, BUT it is still very unusual to have more than 100 in series with the
audio chain, just as I originally stated.
I guess you could possibly achieve it, *IF* that was your aim. And it would
probably still measure fairly blameless in any case.

While you're staring at all the chips next time, why not actually shove a
test signal in and measure the result at the output. I think you will not
find any significant problems unless it is broken.

MrT.

 

[Peter Larsen]

Peter Larsen wrote:

That's not what we're talking about.

True, this is about audibiity of distortion and the subtopic whether
audibility is increased due to musical dissonance between distortion
components and actual tones and overtones.

The example that makes me prone to aassume that William has a point is
the experience of overall improvement of tonal purity in recorded music
once 50 Hz hum and its overtones have been filtered out.

IF this tonal purity issue applies also for distortion components, then
out of tune distortion could be a cause of general grungyness to a
larger extent than in tune distortion, out of tune nad in tune
constituting references to the tempered scale.

You can tune most instruments to these scales.

Unless they have to play with tempered instruments.

So as to not spread this over multiple follow ups I will toss in a
comment to Dick here: the point made, I think it was by William, is
about disharmonic harmonic distortion possibly being more audible than
harmonic distortion, harmonic distortion will occur on frequencies that
are disharmonic compared to a tempered tuning as I have understood this,
consequently it is not about masking of the distortion components per
se. But I probably have a lot to learn about also this.

Graham

Kind regards

Peter Larsen

 

[Arny Krueger]

This is not about masking, it is about pitch, and pitch is acutely
heard.

True, but...

You've got to reliably perceive a sound before you can tell what pitch it
is. Masking can keep you from totally perceiving a certain sound in any
way.

As I said before, many musical instruments have overtones that are not
exactly harmonically related to the fundamental. The usual rules of masking
apply to those overtones, as well.

Bottom line, the audibility of nonlinear distortion is not contingent on
different types of musical scales or whether you use A=440 or some other
base pitch.

 

[Arny Krueger]

The technical definition of an overtone is no different from a harmonic
other than
its number.

1st overtone = 2nd harmonic etc.

Overtones are a superset of the set of harmonics:

Wikipedia:

"

Overtone:

An overtone is a sinusoidal component of a waveform, of greater frequency
(usually an integer number multiple) than its fundamental frequency. The
term is usually used in music, rather than wave physics. (see standing wave)

Harmonic:
In acoustics and telecommunication, the harmonic of a wave is a component
frequency of the signal that is an integer multiple of the fundamental
frequency. For example, if the frequency is f, the harmonics have frequency
2f, 3f, 4f, etc. The harmonics have the property that they are all periodic
at the signal frequency, and due to the properties of Fourier series, the
sum of the signal and its harmonics is also periodic at that frequency.

Many oscillators, including the human voice, a bowed violin string, or a
Cepheid variable star, are more or less periodic, and thus can be decomposed
into harmonics.

Most passive oscillators, such as a plucked guitar string or a struck drum
head or struck bell, naturally oscillate at several frequencies known as
overtones. When the oscillator is long and thin, such as a guitar string, a
trumpet, or a chime, the overtones are still integer multiples of the
fundamental frequency. Hence, these devices can mimic the sound of singing
and are often incorporated into music. Overtones whose frequency is not an
integer multiple of the fundamental are called inharmonic and are often
perceived as unpleasant.

The untrained human ear typically does not perceive harmonics as separate
notes. Instead, they are perceived as the timbre of the tone. In a musical
context, overtones which are not exactly integer multiples of the
fundamental are known as inharmonics. Inharmonics which are not close to
harmonics are known as partials. Bells have more clearly perceptible
partials than most instruments. Antique singing bowls are well known for
their unique quality of producing multiple harmonic overtones or
multiphonics.

The tight relation between overtones and harmonics in music often leads to
their being used synonymously in a strictly musical context, but they are
counted differently leading to some possible confusion.

"

That itself has no relation to the production of 'harmonics' that are not
integer
multiples of the fundamental. I'd like to see some more evidence of this
alleged
behaviour too.

See the Wikipedia article about harmonics, above.

In general, percussion instruments (including stringed instruments that use
struck or plucked strings) have equations of motion that are nonlinear
enough that there are inharmonic overtones.

 

[[email protected]]

But who's still using those old tunings ?

Almost every performer of music written in those times when
these tunings prevailed. Almost all modern performances
of Baroque music and some early classical music pays
attention to this detail. Many modern pipe organs that are
based on historical models use variations of these
temperements.

That being said, the point that the harmonics may be "on"
or "off" is somewhat silly, because it assumes masking
ONLY occurs for exact frequency matches. In fact, masking
is quite broad.

 

[Eeyore]

There are people here knowing vastly more about music than I do, but all
instruments that allow intonation are in my understanding likely to use
or at least approximate those scales unless playing with a tempered
instrument. After all, that is what the intonation advantage is about.

That's not what we're talking about.

You can tune most instruments to these scales.

Graham

 

[Arny Krueger]

That being said, the point that the harmonics may be "on"
or "off" is somewhat silly, because it assumes masking
ONLY occurs for exact frequency matches.

I suspect that some might believe that masking might be less for
non-harmonic overtones because they sound dissonant to some ears. This is
the obvious inverse of what you said.

In fact, masking is quite broad.

Agreed. When a sound is masked it is not perceived, so whether its harmonic
or not is irrelevant.

 

[William Sommerwerck]

Agreed. When a sound is masked it is not perceived, so whether

its harmonic or not is irrelevant.

Arny, this is "proof by assumption".

The issue is whether harmonic distortion is less audible in a tuning system
using whole-number ratios.

Given the claimed "broadness" of masking effects, I'm willing to accept the
idea that tuning has little or no effect on the audibility of harmonic
distortion. What I originally posted was speculation.

 

[Arny Krueger]

Arny, this is "proof by assumption".

No, it is proof by construction.

The issue is whether harmonic distortion is less audible in a tuning
system
using whole-number ratios.

Right, and the answer is generally known in informed circles. That knowlege
is based on both logic and observation.

Given the claimed "broadness" of masking effects, I'm willing to accept
the
idea that tuning has little or no effect on the audibility of harmonic
distortion. What I originally posted was speculation.

I'm happy to accept it as speculation. No harm, no foul if speculation turns
out to fail logical and practical tests. That one reason we call it
speculation and not fact. ;-)

 

[Scott Dorsey]

Not me, but isn't that what you are doing?
No.


Sure, BUT it is still very unusual to have more than 100 in series with the
audio chain, just as I originally stated.
I guess you could possibly achieve it, *IF* that was your aim. And it would
probably still measure fairly blameless in any case.

Pull the cover on an SSL 4000 and look inside. Or just look at the
schematic.

While you're staring at all the chips next time, why not actually shove a
test signal in and measure the result at the output. I think you will not
find any significant problems unless it is broken.

Well, what comes out sure sounds a whole lot different than what went in,
so I would suspect a measurement would indicate that too.

Bob Pease has a wonderful classroom demo in which he shows a 1 KC square
wave through a fairly clean op-amp stage, then through a hundred, and
then through a huge board with a thousand op-amps on it. A small error
gets exaggerated substantially.
--scott

 

[Scott Dorsey]

That's not what we're talking about.

You can tune most instruments to these scales.

Except the piano, which you can't really tune to _any_ scale...
--scott

 

[John Larkin]

["Followup-To:" header set to sci.electronics.design.]

The idea that you can 'get away' with sloppy circuitry for replay because the
source was in some way 'impaired' is totally false.

I don't think anybody proposed "sloppy" circuitry for replay. The point is
that studio audio gear is just solid, reliable, conventional good audio
stuff (none of that high-end low-oxygen power cord crap). Plenty of opamps,
plenty of NFB, plenty of digital processing, plenty of all the things that
high-enders loathe.

Since the recording studio already did 90% of the work of completely
destroying the audio signal beyond repair, it doesn't matter how much your
home audio gear adds to that.

Sometimes when I hear the golden earers talk I'm surprised that I can make
out any music at all when listening with my Cantons fed from an old Sony amp
through particularly oxygen-rich cables.

robert

Designing audio playback gear that has PPM distortion levels, and
noise so low it's dominated by the source material and room
background, is now so easy it's not worth discussing. Just grab some
National appnotes and opamp datasheets. Because it's so easy to make
measurable noise and distortion vanishingly small, the audiophools
have had to move on to debating the unmeasurable, in long threads with
no content.

John

 

[Mogens V.]

Except the piano, which you can't really tune to _any_ scale...
--scott

About the same with a guitar, which can be tuned open string or using
some tuning strategy, but even with a fretjob based on i.e. the
Buzz-Feiten system (or other semilar systems), it'll be a Bit out of
tune most everywhere on the scale.

I find this whole discussion very interesting for understanding sound
quality both for recording and replaying, and most cirtainly also the
other way around, for _creating_ a tone/sound.
As always, I learn a lot in here..


The discussion on intonation struck me. Most western music is pretty
simple in terms of intonation. But try listening to ethnic culture
music, like an African choir or Indian music; can be quite defferent..
As a progressive metal guitar player, I often create dissonant chords,
and lately started experimenting with out of scale string bending, kinda
like using a micro-scale fretted instrument.

Given the 'right' gear, such chords and scales can sound 'good' (surely
a matter of subjective taste), with other gear such becomes extremely
dissonantly unpleasing.
It's an example of understanding electronics WRT tone creation, though
AFAICS is equally related to being able to record and reproduse such.

 

[Peter Larsen]

The discussion on intonation struck me. Most western music
is pretty simple in terms of intonation.

You need to listen more to classical string quartets performing live.

In your own genre you need to listen to early Velvet Underground and
Mothers of Invention, neither were very adept at tuning their
instruments initially ... O;-) ... Velvet Underground especially had
their very own tonal landscape.

Mogens V.

Kind regards

Peter Larsen

 

[Kevin Aylward]

Overtones are a superset of the set of harmonics:

Wikipedia:

"

Overtone:

An overtone is a sinusoidal component of a waveform, of greater
frequency (usually an integer number multiple) than its fundamental
frequency. The term is usually used in music, rather than wave
physics. (see standing wave)

I disagree with this.

An overtone is the natural resonances of a sound source. That is, the
natural modes of vibration. I disagree that the definition has anything to
do with integral multiples of a fundamental. It just so happens that
overtones are often quite close to harmonics. For example, the 2nd overtone
of a drum is 2.4 times its fundamental (given by the roots of Jo, the Bessel
function).

For example, even guitar "harmonics" are not harmonics. The string does not
vibrate exactly at a length set by the nut and bridge. The string does not
move until it is a little away from its fulcrums. This is aproximinatly a
fixed length, that depends on the string thichness/mass density/stiffness. A
first order correction to this is to angle the bridge so that the thinner
strings are shorter than the thicker strings. The net effect is that string
overtones are not integral multiples of a fundamental as halving the string
length, does not half the actual vibration length.

This effect is even more pronounced in brass instruments. This why they have
a bell at the end. Not as a horn to make it louder, but as end correction to
make the thing play nearer to regular harmonics.

When one does the standard physics of blown tubes etc, in 101 whatever, it
is easier to forget that these treatments are just approximations for
drunken students who would rather have their bell end sucked than blowed.

 

[Terry Given]

I disagree with this.

An overtone is the natural resonances of a sound source. That is, the
natural modes of vibration. I disagree that the definition has anything to
do with integral multiples of a fundamental. It just so happens that
overtones are often quite close to harmonics. For example, the 2nd overtone
of a drum is 2.4 times its fundamental (given by the roots of Jo, the Bessel
function).

For example, even guitar "harmonics" are not harmonics. The string does not
vibrate exactly at a length set by the nut and bridge. The string does not
move until it is a little away from its fulcrums. This is aproximinatly a
fixed length, that depends on the string thichness/mass density/stiffness. A
first order correction to this is to angle the bridge so that the thinner
strings are shorter than the thicker strings. The net effect is that string
overtones are not integral multiples of a fundamental as halving the string
length, does not half the actual vibration length.

This effect is even more pronounced in brass instruments. This why they have
a bell at the end. Not as a horn to make it louder, but as end correction to
make the thing play nearer to regular harmonics.

When one does the standard physics of blown tubes etc, in 101 whatever, it
is easier to forget that these treatments are just approximations for
drunken students who would rather have their bell end sucked than blowed.

best post yet, Kevin

Cheers
Terry