how would you use an oscilloscope to measure a sine wave?

[Jeff Liebermann]

On Tue, 22 Dec 2015 21:26:20 -0000, MJC <gravity@mjcoon.plus.com>
wrote:

In article <i1cj7bhpur6bafo0i83h6eba1muf81bt2p@4ax.com>,
jeffl@cruzio.com says...
So, it might also have been possible to inspect the horns harmonic
content, if the player could hold a steady note.

Which reminds me that in a holiday job between school and college I
spent some time chatting up the test engineers who were checking an
audio amplifier. They just used a sine wave signal and listened on
speakers. So I leant on the speaker and whistled a beating note. The
technician spent a minute or two hunting for the source of the beats
until I ran out of breath and got chased out of the test bay...

Mike.

You're evil. I like that.

In roughly 1968, I worked in a shop that did warranty repairs on
various consumer audio equipment, mostly tape recorders. The owner
was rather cheap and decided we could do without much test equipment.
We had one ancient DuMont scope, which was only rarely used.
<http://www.radiomuseum.org/r/dumont_la_oscilloscope_304_a304.html>
When it came time to check for distortion or other audio anomalies,
instead of test equipment, we had Mario.

Mario had zero mechanical ability. Give him a soldering iron and he
was as likely to burn himself as solder the connection. If there was
a cable on the floor, he would find it and trip over it. If he tried
to fix anything, it was usually cosmetically ruined. Most of the
vehicles in the parking lot had dents from his futile attempts to park
his car. By all reason and logic, Mario was not suitable for working
in a repair shop.

However, Mario had amazing hearing. Not only could he detect and
identify many forms of audio distortion, but he could identify which
components were likely to be the cause. At one point, we hired a
clueless student, who knew little about electronics except how to
solder, to just replace the components that Mario identified. The
batting average was amazingly high. I even tried to trick Mario by
creating problems. He did quite well with up to four simultaneously
failed components. More was considered not worth repairing. When
Mario caught a cold or flu, we all took a short vacation, as nothing
was getting fixed using what little test equipment we had.




--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[isw]

In article <56799ed2$0$26104$e4fe514c@textnews.kpn.nl>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:

On 22.12.15 19:48, Tim R wrote:
On Tuesday, December 22, 2015 at 12:53:50 PM UTC-5, amdx wrote:
To do that you need to know the shape of a sine wave... perfectly.
You could use a dual trace and compare a sine wave to your trumpet note.

Or use your computer sound card and see what you really have.

Yes, in 2015 I can do this, and have.

My suspicion was that it was not really possible in 1956 to have done what
he claimed to have done. I figured in the time domain the most you would
see is a tiny ripple on a scope trace, maybe not detectable. But I asked
the question here because you all actually know how to use scopes (and some
of you may be old enough to remember 1950s scopes).

Just use a signal generator on the second scope channel,
switch to x/y mode, and produce an ellipse/circle slowly
rotating.
Distortions will show up quite well.
Even in 1950.

Hoe many trumpeters do you know who can hold a pitch that accurately
(essentially zero error for a slow rotation) for that long?

Isaac

 

[Sjouke Burry]

On 23.12.15 5:43, isw wrote:

In article <56799ed2$0$26104$e4fe514c@textnews.kpn.nl>,
Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> wrote:

On 22.12.15 19:48, Tim R wrote:
On Tuesday, December 22, 2015 at 12:53:50 PM UTC-5, amdx wrote:
To do that you need to know the shape of a sine wave... perfectly.
You could use a dual trace and compare a sine wave to your trumpet note.

Or use your computer sound card and see what you really have.

Yes, in 2015 I can do this, and have.

My suspicion was that it was not really possible in 1956 to have done what
he claimed to have done. I figured in the time domain the most you would
see is a tiny ripple on a scope trace, maybe not detectable. But I asked
the question here because you all actually know how to use scopes (and some
of you may be old enough to remember 1950s scopes).

Just use a signal generator on the second scope channel,
switch to x/y mode, and produce an ellipse/circle slowly
rotating.
Distortions will show up quite well.
Even in 1950.

Hoe many trumpeters do you know who can hold a pitch that accurately
(essentially zero error for a slow rotation) for that long?

Isaac

Long enough to see how distorted the circle/ellipse is.
You control the signal generator, to keep the
frequency almost tracking.
Your eyes and your brain can judge a picture very fast.

 

[isw]

In article <fZWdnbkiXZYUH-TLnZ2dnUU7-XGdnZ2d@supernews.com>,
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 12/22/2015 11:53 AM, Tim R wrote:
On Tuesday, December 22, 2015 at 11:39:49 AM UTC-5, Phil Hobbs
wrote:
On 12/22/2015 11:02 AM, c4urs11 wrote:
On Tue, 22 Dec 2015 05:59:52 -0800, Tim R wrote:

However, my question is about how you would use a 1950s era
scope to determine a sine wave or the degree of harmonics
present.

Scopes from that era easily reached several MHz of bandwidth.
That should be considered adequate to inspect audio signals.

Cheers!


The eyeball is a really lousy detector of harmonics, though,
especially odd harmonics.

Plus he had to use a 1950s-era microphone, so the scope bandwidth
is irrelevant.


I've used an RTA, but those hadn't been invented yet. Before my
time, but wasn't there something called octave filters?

The experimenter wasn't real detailed but supposedly he could tell
from looking at the scope that it was a pure sine without harmonics.

Well, he was wrong about that. Even 10% third harmonic isn't easy to
spot unless you have a comparison sine wave on the screen at the same
time. (I'm thinking about zero degrees relative phase, so the peaks are
symmetrical. It's a bit easier to see at other phases.)

I was very skeptical that 1950s technology allowed that.

Unless he had a really expensive ribbon mic, his 1950s microphone had a
heavy diaphragm and rolled off really badly above about 5 kHz. (One of
the audio guys will correct this, but it's roughly right.)

Condenser mics were not common at that time, but certainly were not
rare, either. The Altec 21B went to 15 kHz, which would handle the
overtones of any real-world musical instrument easily.

Isaac

 

[John Heath]

On Wednesday, December 23, 2015 at 1:58:11 AM UTC-5, isw wrote:

In article <fZWdnbkiXZYUH-TLnZ2dnUU7-XGdnZ2d@supernews.com>,
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

On 12/22/2015 11:53 AM, Tim R wrote:
On Tuesday, December 22, 2015 at 11:39:49 AM UTC-5, Phil Hobbs
wrote:
On 12/22/2015 11:02 AM, c4urs11 wrote:
On Tue, 22 Dec 2015 05:59:52 -0800, Tim R wrote:

However, my question is about how you would use a 1950s era
scope to determine a sine wave or the degree of harmonics
present.

Scopes from that era easily reached several MHz of bandwidth.
That should be considered adequate to inspect audio signals.

Cheers!


The eyeball is a really lousy detector of harmonics, though,
especially odd harmonics.

Plus he had to use a 1950s-era microphone, so the scope bandwidth
is irrelevant.


I've used an RTA, but those hadn't been invented yet. Before my
time, but wasn't there something called octave filters?

The experimenter wasn't real detailed but supposedly he could tell
from looking at the scope that it was a pure sine without harmonics.

Well, he was wrong about that. Even 10% third harmonic isn't easy to
spot unless you have a comparison sine wave on the screen at the same
time. (I'm thinking about zero degrees relative phase, so the peaks are
symmetrical. It's a bit easier to see at other phases.)

I was very skeptical that 1950s technology allowed that.

Unless he had a really expensive ribbon mic, his 1950s microphone had a
heavy diaphragm and rolled off really badly above about 5 kHz. (One of
the audio guys will correct this, but it's roughly right.)

Condenser mics were not common at that time, but certainly were not
rare, either. The Altec 21B went to 15 kHz, which would handle the
overtones of any real-world musical instrument easily.

Isaac

Interesting foot note. A condenser microphone has a small plastic disk inside that is always + on one side and - on the other. It is a charged condenser that can never be discharged no matter how you try to short it out. The molecules inside the plastic disk are frozen that way somewhat like a permanent magnet.

Anyways to the subject at hand. If a guitar string is plucked in the middle of the guitar it makes a sound. If the string is plucked close to the bridge it makes a different sound rich in higher harmonics. The difference between middle and bridge is the difference between sine wave and sine wave plus higher harmonics. In short your ear can detect a sine wave without the need of a oscilloscope. The same is true when repairing a graphic equalizer. The first time we bring out the guns with oscilloscopes , spectrum analyzers and sweep generators. By about the tenth time doing this you just use a Beatles song and let your ear tell you if the graphic EQ is okay or needs sliders cleaned or what not.

 

"Well, he was wrong about that. Even 10% third harmonic isn't easy >to
spot unless you have a comparison sine wave on the screen at the same
time. "

And that's if you know what you're looking for. Personally, I think I could detect lower, but I am not the norm. Second order harmonics should be easier to detect with the aid of the "invert" button.

I have come to the conclusion that an invert on at least one channel is essential.

Anyway, I think the trumpet might be near sine wave at its upper ranges. Just from my ears a can guarantee it is not at the lower ones. Listen to, shit, wait a minit...

https://www.youtube.com/watch?v=HX1t9yy-vmo

Most of the aggregation (is that the right word ?) of the sound is the attack and decay of course, but there is a wah wha part of it. Later, he gets up to the higher notes, and then some of those could be sine waves. That horn is a certain size and all that and the response does roll off at a certain frequency just like a speaker.

At that whole system's highest possible resonant frequencies, the output must approach a sine wave.

I would go get you Pink Floyd - Dogs Of War for the super high notes on the saxophone. Unfortunately I can't find the right version in good enough time, it is late. But I suspect alot of wind instruments approach a sine wave at the upper end of their range.

 

[Tim R]

On Tuesday, December 22, 2015 at 6:21:31 PM UTC-5, Bennett Price wrote:

Could you give a citation, reference (or even a URL) to the article.
I'd love to read it.
Thanks

Sure. At the risk of veering off topic, so with apologies.

Background: For centuries musicians have ascribed tone properties to the materials instruments are made of, while physicists shake their heads because the math seems to say that given sufficient wall thickness the material should make no difference. Physicists who play an instrument are of course caught in the middle.

When the argument gets rehashed, which happens frequently, the skeptics point to the Smith review:
http://la.trompette.free.fr/Smith/IOA/material.htm
There are of course many more papers than that that didn't find a difference but that's the easiest to find and understand. It reviews 13 of the better studies. It isn't that easy to make two identical instruments of different materials, or in fact two identical ones of the same material.

There are only two "studies" that get quoted by the true believers: the Schilke study, quoted here:
http://www.dallasmusic.org/schilke/Brass%20Clinic.html
which is the one under discussion currently. You can see there is no date, no description, no publication, it's just a handout from a sales convention.
The other one is the famous Conn study which suffers from the same absence of the actual original report so it gets quoted by both sides.

 

[Bennett]

On 12/23/2015 5:09 AM, Tim R wrote:

On Tuesday, December 22, 2015 at 6:21:31 PM UTC-5, Bennett Price wrote:

Could you give a citation, reference (or even a URL) to the article.
I'd love to read it.
Thanks

Sure. At the risk of veering off topic, so with apologies.

Background: For centuries musicians have ascribed tone properties to the materials instruments are made of, while physicists shake their heads because the math seems to say that given sufficient wall thickness the material should make no difference. Physicists who play an instrument are of course caught in the middle.

When the argument gets rehashed, which happens frequently, the skeptics point to the Smith review:
http://la.trompette.free.fr/Smith/IOA/material.htm
There are of course many more papers than that that didn't find a difference but that's the easiest to find and understand. It reviews 13 of the better studies. It isn't that easy to make two identical instruments of different materials, or in fact two identical ones of the same material.

There are only two "studies" that get quoted by the true believers: the Schilke study, quoted here:
http://www.dallasmusic.org/schilke/Brass%20Clinic.html
which is the one under discussion currently. You can see there is no date, no description, no publication, it's just a handout from a sales convention.
The other one is the famous Conn study which suffers from the same absence of the actual original report so it gets quoted by both sides.

Warning Off topic:

Thanks for the references. (I found the 'effect of lacquer' portion of
Schilke's article really interesting and perhaps even convincing as my
girl friend is considering de-lacquering her french horn) I play
clarinet and the same sort of controversy exists for woodwinds -
grenadilla vs. rosewood vs. delrin vs. ebonite vs. rubber, etc. In
clarinets, it is clear that the performers are much more important than
the composition of the instrument on which they're playing. But it's
almost next to impossible to compare apples to apples since, as with
brass instruments, the clarinets made of different materials also have
different bore dimensions, undercutting, and other dimensional
variations. And of course even with 2 instruments made of identical
materials, one may cost $300, the other ten times as much.
And 2 'identical' instruments, same make/model/vintage, may have subtle
differences, particularly in intonation.

 

[Michael A. Terrell]

John Heath wrote:

Interesting foot note. A condenser microphone has a small plastic disk inside that is always + on one side and - on the other. It is a charged condenser that can never be discharged no matter how you try to short it out. The molecules inside the plastic disk are frozen that way somewhat like a permanent magnet.

You are describing an Electret Microphone. It is a subset of
Condenser Microphones. The others require a very well filtered high
voltage source to keep the condenser charged.

 

>"differences, particularly in intonation"

By intonation do you mean the same thing as when you set up the neck of a guitar ? On a guitar you basically set the twelfth fret to be exactly one octave up. I do not know about other instruments much. Fretless stringed instruments I guess you can set however you want, but that is not going to be true of brass, wood or wind.

Or are you talking about the harmonics ? The word intonation could be taken as that, and rightly by certain people who are talking about the tonal quality rather than the tone itself. Which is it ?

What's more, is there a way to set intonation, like on a guitar, on saxes, clarinets, and all that ?

I am a bit curious about all this.

 

I took your use of the word intonation in the wrong context because not alot of people know about the musical instrument aspect of it.

I have made myself and a few guitarists happy by setting the neck so they play nice and easy. Usually on electric guitars, very few acoustics are adjustable, at least that I have seen. Also, recently (to me that is like five years) I learned how to set up and tune a violin. Of course without frets you can make it how you want it. With frets it has to be right.

Hmm, OK trumpets and whatever need to be tuned, but what about a trombone ?

 

[Bennett Price]

On 12/24/2015 10:00 PM, jurb6006@gmail.com wrote:

"differences, particularly in intonation"

By intonation do you mean the same thing as when you set up the neck of a guitar ? On a guitar you basically set the twelfth fret to be exactly one octave up. I do not know about other instruments much. Fretless stringed instruments I guess you can set however you want, but that is not going to be true of brass, wood or wind.

Or are you talking about the harmonics ? The word intonation could be taken as that, and rightly by certain people who are talking about the tonal quality rather than the tone itself. Which is it ?

What's more, is there a way to set intonation, like on a guitar, on saxes, clarinets, and all that ?

I am a bit curious about all this.

I'm using 'intonation' to mean proper well-tempered tuning, e.g., C mid-
staff should be precisely an octave (2x the frequency) of middle-C below
the staff. On clarinets each note should be in well-tempered tuning
with every other; that doesn't happen. As well, there's a 'register
key' when opened that is supposed to raise the pitch a perfect 12th -
this doesn't work out as it ideally should. A middle-C (right below the
staff) goes up to a top-line G when the register key is opened - it
should be a perfect 12th but it rarely is. Instrument designers do the
best can to make their instruments completely in tune with themselves
but it is impossible due to the '12th key'. All the holes that
determine pitch (along with the bore dimensions, barrel, bell,
mouthpiece, reed and players oral cavity) have an effect on the pitch.

I should add, as well, that the clarinet, within reason, can be tuned to
other instruments by pulling out the barrel and/or middle joint. This
is routinely necessary as the instrument warms up and thus goes up in pitch.

Intonation in the other sense you're using it, harmonics, are peculiar
to the clarinet, as they are primarily odd, not even harmonics of the
fundamental.

All of this oddness is due to the fact that the clarinet is basically
cylindrical (not conical like a sax or oboe) and closed at one end
(where the mouthpiece is) unlike a flute.

 

[Phil Allison]

Bennett Price wrote:

Intonation in the other sense you're using it, harmonics, are peculiar
to the clarinet, as they are primarily odd, not even harmonics of the
fundamental.

All of this oddness is due to the fact that the clarinet is basically
cylindrical (not conical like a sax or oboe) and closed at one end
(where the mouthpiece is) unlike a flute.

** Ah, this explains the clarinet producing acoustic square waves.

A combination of fundamental tone, third, fifth and seventh harmonics.



..... Phil

 

[Tim R]

On Friday, December 25, 2015 at 6:16:13 PM UTC-5, jurb...@gmail.com wrote:



> Hmm, OK trumpets and whatever need to be tuned, but what about a trombone ?

Like most brass instruments a trombone comes with a main tuning slide. It is a U shaped piece of tubing right on the top (behind your head when you're playing). You set that for the group you're playing with.

But you also make fine adjustments with the slide that moves. Trombone is "fretless" just like a violin. The slide has an approximately correct position but it always has to be slightly fine tuned for every note, because there are many notes in each position but all have tendencies to be sharp or flat, and notes sometimes have to be adjusted sharp or flat because of the musical context.

I've been playing in various groups for most of the past 50 years, and I've observed a recent tendency to standardize pitch much more. In the 60s a Stroboconn tuning machine cost $2600, which was more than a car back then. Now everybody has a $20 electronic tuner that is just as accurate. While not everybody uses them correctly, the overall effect is that groups have a central pitch much closer to 440 than in the old days.

 

[John Heath]

On Friday, December 25, 2015 at 9:58:08 PM UTC-5, Tim R wrote:

On Friday, December 25, 2015 at 6:16:13 PM UTC-5, jurb...@gmail.com wrote:



Hmm, OK trumpets and whatever need to be tuned, but what about a trombone ?

Like most brass instruments a trombone comes with a main tuning slide. It is a U shaped piece of tubing right on the top (behind your head when you're playing). You set that for the group you're playing with.

But you also make fine adjustments with the slide that moves. Trombone is "fretless" just like a violin. The slide has an approximately correct position but it always has to be slightly fine tuned for every note, because there are many notes in each position but all have tendencies to be sharp or flat, and notes sometimes have to be adjusted sharp or flat because of the musical context.

I've been playing in various groups for most of the past 50 years, and I've observed a recent tendency to standardize pitch much more. In the 60s a Stroboconn tuning machine cost $2600, which was more than a car back then. Now everybody has a $20 electronic tuner that is just as accurate. While not everybody uses them correctly, the overall effect is that groups have a central pitch much closer to 440 than in the old days.

One more step off subject. Apologies in advance. I remember being in a band in my 20s. Those were great years playing local bars. Unfortunately I did not have the magic so I stayed with electronics. What is that magic? I have played with some greats and it always surprises myself how they can hear a song one time and just run with it while I have to work for it. Ask Sammy Davis Jr what key to play in and he will say whiskey. What is that magic?

 

[Bennett Price]

On 12/25/2015 8:33 PM, Ralph Mowery wrote:

"Tim R" <timothy42b@aol.com> wrote in message
news:b2ec33a3-0d5a-459b-b67a-a83f95d81ec8@googlegroups.com...
On Friday, December 25, 2015 at 6:16:13 PM UTC-5, jurb...@gmail.com wrote:


Like most brass instruments a trombone comes with a main tuning slide. It
is a U shaped piece of tubing right on the top (behind your head when
you're >playing). You set that for the group you're playing with.

But you also make fine adjustments with the slide that moves. Trombone is
"fretless" just like a violin. The slide has an approximately correct
position but it always has to be slightly fine tuned for every note,
because there are many notes in each position but all have tendencies to be
sharp or flat, and notes >sometimes have to be adjusted sharp or flat
because of the musical context.

I've been playing in various groups for most of the past 50 years, and I've
observed a recent tendency to standardize pitch much more. In the 60s a
Stroboconn tuning machine cost $2600, which was more than a car back then.
Now everybody has a $20 electronic tuner that is just as accurate. While
not everybody uses them correctly, the overall effect is that groups have a
central >pitch much closer to 440 than in the old days.

Around 1964 our Jr High had a band program and had one of the Stroboconn
machine. I thought it was called a Stroboscope, but hard to remember what
it was from over 40 years ago. Maybe the band director called it wrong
then.

I do remember the trombones being adjusted like you said. P:iece on the
back was moved in or out. I never did know how they could move the slide in
and out for the different notes and get them right. I think the band
directors favorite note was a B to set everyone to.

The strobe tuner of yore is still available:
https://www.petersontuners.com/shop/Mechanical-Strobe-Tuners

 

[Tim R]

On Saturday, December 26, 2015 at 1:23:15 PM UTC-5, Bennett Price wrote:

On 12/25/2015 8:33 PM, Ralph Mowery wrote:
"Tim R" <timothy42b@aol.com> wrote in message
news:b2ec33a3-0d5a-459b-b67a-a83f95d81ec8@googlegroups.com...
On Friday, December 25, 2015 at 6:16:13 PM UTC-5, jurb...@gmail.com wrote:


Like most brass instruments a trombone comes with a main tuning slide. It
is a U shaped piece of tubing right on the top (behind your head when
you're >playing). You set that for the group you're playing with.

But you also make fine adjustments with the slide that moves. Trombone is
"fretless" just like a violin. The slide has an approximately correct
position but it always has to be slightly fine tuned for every note,
because there are many notes in each position but all have tendencies to be
sharp or flat, and notes >sometimes have to be adjusted sharp or flat
because of the musical context.

I've been playing in various groups for most of the past 50 years, and I've
observed a recent tendency to standardize pitch much more. In the 60s a
Stroboconn tuning machine cost $2600, which was more than a car back then.
Now everybody has a $20 electronic tuner that is just as accurate. While
not everybody uses them correctly, the overall effect is that groups have a
central >pitch much closer to 440 than in the old days.

Around 1964 our Jr High had a band program and had one of the Stroboconn
machine. I thought it was called a Stroboscope, but hard to remember what
it was from over 40 years ago. Maybe the band director called it wrong
then.

I do remember the trombones being adjusted like you said. P:iece on the
back was moved in or out. I never did know how they could move the slide in
and out for the different notes and get them right. I think the band
directors favorite note was a B to set everyone to.




The strobe tuner of yore is still available:
https://www.petersontuners.com/shop/Mechanical-Strobe-Tuners

check this out, it explains the circuit (back on topic for the forum)

http://home.grandecom.net/~garybrookshire/files/conn%20st-1%20manual.pdf