** My colleague, Rod Elliot of ESP has come across a little publicised
phenomenon regarding IM distortion.

The fact is easily demonstrated that if two sine (or near sine) tones are
fed into a symmetrical ( ie diode) clipper, NO sum and NO difference
frequency are generated.

Many other frequency products are created, but NOT the simple sum and
difference ones that are so often assumed to exist.

I have independently verified Rod's findings using FFT analysis and
listening tests.

A new article on the matter is now on the ESP site:

http://sound.westhost.com/articles/intermodulation.htm

The phenomenon has intriguing implications for " two tone " IM testing of
audio gear and also may go a long way towards explaining why it has long
been considered important to have a well balanced, push pull output stage in
a valve/tube guitar amplifier.

The production of strong difference tones when playing simple chords into
distortion would not be liked by many musicians.



.... Phil

On Tue, 25 Sep 2012 16:36:32 +1000, "Phil Allison"
wrote:


** My colleague, Rod Elliot of ESP has come across a little publicised
phenomenon regarding IM distortion.

The fact is easily demonstrated that if two sine (or near sine) tones are
fed into a symmetrical ( ie diode) clipper, NO sum and NO difference
frequency are generated.

Many other frequency products are created, but NOT the simple sum and
difference ones that are so often assumed to exist.

I have independently verified Rod's findings using FFT analysis and
listening tests.

A new article on the matter is now on the ESP site:

http://sound.westhost.com/articles/intermodulation.htm

The phenomenon has intriguing implications for " two tone " IM testing of
audio gear and also may go a long way towards explaining why it has long
been considered important to have a well balanced, push pull output stage in
a valve/tube guitar amplifier.

The production of strong difference tones when playing simple chords into
distortion would not be liked by many musicians.



... Phil



Sum and difference are not the tones you look for in an intermod test.
If I am testing for intermod, I will inject 1000 and 1100 Hz. The
intermod products are then 900 and 1200 Hz. They are present whatever
kind of distortion the amplifier has.

Sum and difference tones are s quasi-linear mixing (f1 x f2) product.

d

"Don Pearce = Lying Pig "

Sum and difference are not the tones you look for in an intermod test.


** Absolute ********.

IMD in audio is tested by the SMPTE/DIN method or the newer ITU-R standard.

The ITU-R method tests purely for the difference frequency.

http://www.rane.com/par-i.html


If I am testing for intermod, I will inject 1000 and 1100 Hz.


** Nobody gives a flying **** what one puffed up, pommy **** like Don does.


..... Phil

On Tue, 25 Sep 2012 17:14:57 +1000, "Phil Allison"
wrote:


"Don Pearce = Lying Pig "

Sum and difference are not the tones you look for in an intermod test.


** Absolute ********.

IMD in audio is tested by the SMPTE/DIN method or the newer ITU-R standard.

The ITU-R method tests purely for the difference frequency.

http://www.rane.com/par-i.html


If I am testing for intermod, I will inject 1000 and 1100 Hz.


** Nobody gives a flying **** what one puffed up, pommy **** like Don does.


.... Phil



Sum and difference products can be produced with no intermod whatever.
The mixer circuit in any radio is an example. A good one is highly
linear, has no intermod, and produces only the sum and difference
frequencies - the originals are suppressed. I say again, sum and
difference are not a measure of intermod performance. The clue is in
the "mod" part of the name. It is a modulation process that produces
sidebands spaced away from the incoming tones by the difference
frequency.

d

On 25/09/2012 08:14, Phil Allison wrote:
"Don Pearce = Lying Pig"

Sum and difference are not the tones you look for in an intermod test.


** Absolute ********.

IMD in audio is tested by the SMPTE/DIN method or the newer ITU-R standard.

The ITU-R method tests purely for the difference frequency.

http://www.rane.com/par-i.html


If I am testing for intermod, I will inject 1000 and 1100 Hz.


** Nobody gives a flying **** what one puffed up, pommy **** like Don does.


.... Phil



Question-
What's the difference between yoghurt and Australia?
There's real live culture in yoghurt.
--

"Don Pearce = Lying Pig "


Sum and difference are not the tones you look for in an intermod test.


** Absolute ********.

IMD in audio is tested by the SMPTE/DIN method or the newer ITU-R standard.

The ITU-R method tests purely for the difference frequency.

http://www.rane.com/par-i.html


If I am testing for intermod, I will inject 1000 and 1100 Hz.


** Nobody gives a flying **** what one puffed up, pommy **** like Don does.

FOAD you stupid ****.



..... Phil

On Tue, 25 Sep 2012 22:17:39 +1000, "Phil Allison"
wrote:


"Don Pearce = Lying Pig "


Sum and difference are not the tones you look for in an intermod test.


** Absolute ********.

IMD in audio is tested by the SMPTE/DIN method or the newer ITU-R standard.

The ITU-R method tests purely for the difference frequency.

http://www.rane.com/par-i.html


If I am testing for intermod, I will inject 1000 and 1100 Hz.


** Nobody gives a flying **** what one puffed up, pommy **** like Don does.

FOAD you stupid ****.



.... Phil


You can go on repeating that til you are blue in the face. It is
wrong.

d

"Don Pearce = Lying Pig "


Sum and difference are not the tones you look for in an intermod test.


** Absolute ********.

IMD in audio is tested by the SMPTE/DIN method or the newer ITU-R
standard.

The ITU-R method tests purely for the difference frequency.

http://www.rane.com/par-i.html


If I am testing for intermod, I will inject 1000 and 1100 Hz.


** Nobody gives a flying **** what one puffed up, pommy **** like Don
does.

FOAD you stupid ****.


You can go on repeating that til you are blue in the face. It is
wrong.



** That Don Pearce is a bull****ting, colossally pedantic **** is 100%
correct.

What the ASD ****ed fool imagines is right or wrong is merely another
symptom his insanity.

FFS - the cretinous ****wit even believes in " Cramolin" scam.





.... Phil