It can be shown that IM products related to 2'd or even 3'rd harmonic are musically related to the original material, and like low order harmonic distortion, are not easily detected because they just change the music only slightly. It is the higher order odd harmonics and their IM byproducts that are important in general.
In fact, many studios can 'sweeten' tracks by adding 2'nd harmonic using an overdriven vacuum tube on purpose.
However, 3% of anything is too much, except on occasional peaks.
In fact, many studios can 'sweeten' tracks by adding 2'nd harmonic using an overdriven vacuum tube on purpose.
However, 3% of anything is too much, except on occasional peaks.
I don't think that's fair. We all make inconsistent choices one way or another. Sometimes I like a beer, sometimes I like a glass of wine. Does that make my beer choice 'inconsistent' when I take one?
The 'enjoy' word is appropriate here.
There is a difference between claiming that one choice is in some way 'better' than another or simply enjoying what you fancy at a specific moment.
Jan
Of course not, but the example seems miles from what we see here.
We've got people here obsessing over what appears to be good fairly modern resistors in the face of a medium with relatively horrific amounts of noise and distortion, and repeatedly and aggressively verbally abusing people who disagree with them, whether overtly or by innuendo.
This isn't just personal preference, like choosing beer over wine. Its preferring really skunky beer over wine and then belittling everybody who does not share their preference for skunky beer.
But that is not Bill's problem - his problem appears to me to be laziness, ignorance, and pent up anger. Interestingly enough the topic was discussed pretty civilly once before on this thread around post #76650. I see a lot of questionable engineering and deflections obfuscating it there.
Sorry Jan, Have to break ranks..
there is no post #76650 in this thread. So what are you on about?
Laziness: Meh I've been called worse
Ignorance: Are you confusing me with someone else, or do you have a cite for my lack of knowledge?
Pent up anger: Nope I'm chill. Life is good.
I've seen a number of related analysis, but I've never seen anything like that as a general rule. Got a cite?
Obviously, there are specific cases where it can be true, but if its not more general than that, its irrelevant to discussion of whether IM is a problem in audio systems.
Of course not my bad, its in the thread about the blowtorch preamp, which was being discussed at the time.
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what's the second or thrid harmonic of a two signal IMD test?
say we have 19kHz and 20kHz in equal measure, then where are the 2nd & 3rd?
or 7kHz and 15kHz ?
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Good tip, but not much help when someone is trying to use the post's existence for some purpose other than enlightenment. In this case over 110 pages were misrepresented as:
http://www.diyaudio.com/forums/lounge/146693-john-curls-blowtorch-preamplifier-part-ii-7677.html#post4550737
"a few pages".
That's SOP in most cases.
Any thread longer than a few pages has lost it's direction and is useless for getting 'enlightnment' on the original subject; but may still be fun. As is this one ;-)
Jan
Same here 
For enlightment or technical knowledge or, more to the point, Hi Fi state of the Art advancement, this thread is as believable or useful as the annual convention of tribal witch doctors held in some backwards jungle hamlet, with a few distinguished exceptions, but no doubt it's fun.
And besides that I am learning a lot, just it's on Trolling 101, Bad/Twisted Logic II and in general the Sociological or Psychological aspect.
For enlightment or technical knowledge or, more to the point, Hi Fi state of the Art advancement, this thread is as believable or useful as the annual convention of tribal witch doctors held in some backwards jungle hamlet, with a few distinguished exceptions, but no doubt it's fun.
And besides that I am learning a lot, just it's on Trolling 101, Bad/Twisted Logic II and in general the Sociological or Psychological aspect.
To clarify - I believe he's referring to the IM products related to second or third order nonlinear distortion.
Per a quick simulation @ 192 KHz sampling, Second order IM of 19 and 20 KHz creates spurious responses at 1, 38, 39, and 40 KHz
Third order IM of 19 and 20 KHz produces spurious responses at 18, 19, 20, and 21 KHz as well as 57, 58, 59 and 60 KHz.
In the context of music, the signal is far more complex and already composed of both harmonic and aharmonic components.
For example due to the often highly nonlinear mechanics of many musical instruments, many signal components that you might expect to be harmonics are not at exact integer multiples of the fundamental.
As Curl points out, harmonic distortion products created by equipment can possibly fall on top of harmonics or near those that are already in the music and come under the relatively noncritical umbrellas of masking and detection of level shifts. However, these will all be at integer multiples.
As the 19 and 20 KHz above examples show, IM products, even those due to low order nonlinearities are often at frequencies that are widely separated from the audio signals that caused them to be generated.
Thus the the relatively noncritical umbrellas of masking and detection of level shifts may not apply and the spurious responses can become audibly obvious and even disturbing .The worst cases produce spurious responses from less audible frequencies (the extremes of the audible range or beyond) that are at highly audible frequencies (the midband, working up to 4-7 KHz).
The logical approaches to this are either to build equipment that is linear over a very wide range even beyond the audio band, or build equipment that limits response to the audible band. In modern times both approaches are used even concurrently.
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Crazing of glass or other sealant wicking in moisture is a well known problem. The leads on our TO99 electrometers can not be dressed to fit another form factor. We had a customer that was welding TO99's into a standard octal tube lead frame to make their universal plug-in vacuum gauges.
Careful there non-harmonics are not easily generated i.e. NOT related to F1, F2, etc. BTW the pictures of vinyl flaws are posted and discussed here on a cyclical basis.
EDIT - We generally don't consider IM products as being non-harmonic (aharmonic?) whereas an amplifier that oscillates a little on signal peaks can generate true non-harmonic signals
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