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Topic: Digital Simulation of Phonograph Tracking Distortion (Read 6190 times) previous topic - next topic
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Digital Simulation of Phonograph Tracking Distortion

Quote
Phonograph tracking distortion results from the misalignment of a playback cartridge with respect to the cutting head. While it has been researched for decades, it remains a source of mystery: it cannot be isolated, it has not been accurately simulated, and its importance remains undecided. Here, a PCM simulation of horizontal and vertical tracking distortion of extremely high quality is presented, operating on the principle of phase modulation, allowing tracking distortion to be evaluated in isolation with real musical content. In this context, tracking distortion is equivalent to digital audio sampling jitter, with the jitter spectrum equal to the signal spectrum. Implications of this connection, as well as simulation accuracy, preliminary listening test results, and potential applications are discussed.


This is a paper I published at the AES convention this past October because I felt it was important enough to get on the record alongside the literature already available on the subject. You can download the poster I presented on the paper here. The preprint is available here for purchase.

I have some more information up on my blog, including some details on the simulator itself (which I plan to release source and executable for), and on a larger listening test I plan on performing.

(cross-posted from a couple other forums)

Digital Simulation of Phonograph Tracking Distortion

Reply #1 –
Nice one Axon! If I buy the preprint, do you get any sort of kickback?

Digital Simulation of Phonograph Tracking Distortion

Reply #2 –
I don't really understand how you have verified the accuracy of your model vs. reality, i. e. wether the type and amount of analog distortion resulting from tracking error really equates that of your PCM modulation.

When you compare simulated vs. predicted harmonics, both seem to be model values, and not a comparison of model vs. measured values. Or am I missing something?

Digital Simulation of Phonograph Tracking Distortion

Reply #3 –
Quote from: Canar on
Nice one Axon! If I buy the preprint, do you get any sort of kickback?
Nope. It's more or less a small monetary contribution to the AES.

Quote from: rpp3po on
I don't really understand how you have verified the accuracy of your model vs. reality, i. e. wether the type and amount of analog distortion resulting from tracking error really equates that of your PCM modulation.

When you compare simulated vs. predicted harmonics, both seem to be model values, and not a comparison of model vs. measured values. Or am I missing something?
Tracking distortion can be solved analytically for sinusoids, and my simulation matches the analytical solution to a pretty ridiculous degree. (I did a null test and everything nulled out to -120db.) You're correct in saying that this puts a significant asterisk on the applicability of this simulator to real-world decisions, but as far as tracking distortion specifically is concerned, real-world measurements are unnecessary.

Digital Simulation of Phonograph Tracking Distortion

Reply #4 –
Just to understand this better: I give you a tonearm's (or needle's) angle to a groove and from that you can simulate the signature and amount of tracking distortion at that position?

Digital Simulation of Phonograph Tracking Distortion

Reply #5 –
Well, the tonearm angle, plus the groove radius, the rotational velocity and the modulation level are enough for the simulation. Yes.

Digital Simulation of Phonograph Tracking Distortion

Reply #6 –
I had subsumed the plus under position, except for the modulation level. I thought there might be at least basic facilities to approximate that from this input. You'd probably also need force and mass. Nevertheless, good work!