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Old 6th July 2012, 03:45 PM   #24231
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Quote:
Originally Posted by DF96 View Post
If DA really can be heard, then that means that we are sensitive to very tiny deviations in frequency response. If DA apparently produces second harmonic from any waveform then there is a problem with either the measurements or their interpretation as DA cannot do this. Far more likely that DA is a marker for some other dielectric problem. Can we look for that, and stop all this nonsense about DA itself?
Absolutely correct.
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Old 6th July 2012, 04:18 PM   #24232
FrankWW is offline FrankWW  Canada
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If the output is not the same as the input in some fashion, what adjective do we use?

An exxample:
Badly built speakers produce refractive components that sound bad above, say, 80 - 85 dB and sound progressively worse as SPL's increase. On the speaker side it's a linear phenomenon; on the hearing side it's non-linear.

There was a bust up on a speaker thread when a participant (an extremely well qualified engineer/physicist) referred to this as 'linear distortion'. No such thing said another engineer and in so many words accused the first of being incompetent. So what do I call it? said the first guy, there are components in the sound that weren't in the original signal. Yada yada.....
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Old 6th July 2012, 04:33 PM   #24233
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Originally Posted by scott wurcer View Post
Yes, the issue is that the best AC voltage across a cap is no AC voltage. But the true distortion at the -3dB point is due to dielectric properties other than just DA even though they might be related. As for -120dB artifacts being audible please read Dick Burwen's editorial in Linear Audio. Finishing half your beer is more audible in more ways than one.

EDIT - Probably more audible if it was a glass of beer.
Scott,

Using common professional values of 10 microfarads and 600 ohms for a source/load impedance, then the attack wavefront from a drum strike would approach 20% distortion!

You are welcome to try your own measurements or simulations, I would quite legitimately like to see others try it.

ES
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Old 6th July 2012, 05:17 PM   #24234
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Quote:
Originally Posted by simon7000 View Post
Scott,

Using common professional values of 10 microfarads and 600 ohms for a source/load impedance, then the attack wavefront from a drum strike would approach 20% distortion!

You are welcome to try your own measurements or simulations, I would quite legitimately like to see others try it.

ES
ED, I'm sure when we get down to it, it's semantics. Rearranging the phase and amplitude of the frequency components could "dull" a transient 20%, no problem. This is not distortion.

26Hz really? Even Peavy specs -.5dB @ 10Hz which is well below 5Hz corner.
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Old 6th July 2012, 05:45 PM   #24235
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Quote:
Originally Posted by scott wurcer View Post
ED, I'm sure when we get down to it, it's semantics. Rearranging the phase and amplitude of the frequency components could "dull" a transient 20%, no problem. This is not distortion.

26Hz really? Even Peavy specs -.5dB @ 10Hz which is well below 5Hz corner.
10 microfarads at 600 ohm source and load is 13 Hz. That actually happens in pro gear, but that is just a typical value. If you go lower the distortion does drop. We I think can agree on those issues.

But let me ask the question:

If you pass the same compound signal (ADSR x Carrier) through two different high pass RC filters R & C vs R & 100C and compare the waveforms is there a difference in the first cycle of the carrier? (You can use a carrier frequency of 3,000 Hz and an attack of 10db/msec. for 60 db.)

That to me is the issue.
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Old 6th July 2012, 06:21 PM   #24236
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Quote:
Originally Posted by FrankWW View Post
If the output is not the same as the input in some fashion, what adjective do we use?

An exxample:
Badly built speakers produce refractive components that sound bad above, say, 80 - 85 dB and sound progressively worse as SPL's increase. On the speaker side it's a linear phenomenon; on the hearing side it's non-linear.

There was a bust up on a speaker thread when a participant (an extremely well qualified engineer/physicist) referred to this as 'linear distortion'. No such thing said another engineer and in so many words accused the first of being incompetent. So what do I call it? said the first guy, there are components in the sound that weren't in the original signal. Yada yada.....

Interesting point in and by itself. I wouldn't call this distortion however, since refraction leads to local dips and peaks in the FR at different angles from the loudspeaker.

Last edited by vacuphile; 6th July 2012 at 06:31 PM.
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Old 6th July 2012, 06:23 PM   #24237
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Again and again, distinguish between linear (change in amplitude, phase, time response) and non-linear (=distortion, i.e. creation of frequencies not present in the original signal).
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Old 6th July 2012, 06:30 PM   #24238
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Originally Posted by Bonsai View Post
avoid using ceramics (other than NPO/COG) in audio, steer clear of polyester and mylar and one or two others (from Dick Marsh and Walt Jung's article) you should be ok.

Hell, I just realized that doesn't leave much choice ;-)
Thanks, you answered my question about the NPO/COG capacitors.

By the way, what choices are left ?

Last edited by fireworks; 6th July 2012 at 06:34 PM.
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Old 6th July 2012, 06:35 PM   #24239
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Servos look like a good idea. ;-)
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Old 6th July 2012, 06:51 PM   #24240
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Originally Posted by PMA View Post
Again and again, distinguish between linear (change in amplitude, phase, time response) and non-linear (=distortion, i.e. creation of frequencies not present in the original signal).
Yes.

A reference I've found very helpful: Blinchikoff and Zverev, Filtering in the Time and Frequency Domains. It was out of print for a long time, then reissued; not sure what the status is now.

If it were to be revised, today we'd likely have a CD ROM or a website with lots more examples, maybe some animations and even acoustical examples.

Brad
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