Thanks, Doug. A couple of clarifications to my previous post, which are relevant to your "quibbles" :)
By "square wave" I did not mean to refer to something that is truly square, with edges that are nearly vertical, or that even approach being nearly vertical. My reference to "risetime and falltime corresponding to spectral components extending some distance into the ultrasonic region" means that the edges of the waveform would rise and fall in a controlled, somewhat gradual manner. Since risetime and falltime have an inverse relationship to bandwidth, if those parameters were set so as to correspond to a bandwidth of say 30 or 40kHz, and if the amplitude of the signal were small, I would not expect tracking to be much more difficult than for a high frequency low level sine wave.
The point to riaa pre-emphasis would be to make the waveform that is monitored on the scope, at the output of the phono stage or preamp, more readily interpretable by the user, given that the user would be monitoring at a point downstream from riaa de-emphasis. Monitoring the signal at the phono stage input, prior to riaa de-emphasis, may be problematic due to the low signal level, and possibly also due to the effect of probe capacitance on the signal being put out by the SUT.
I vaguely recall that such test records were available way back when, from Shure among others, but I have no knowledge of any that may be available now.
Scopes are very easy to use, btw, following some brief familiarization, and, as you are probably aware, are potentially useful for optimizing some tonearm settings as well.
Basically, as I see it, the process of optimizing SUT/cartridge loading is attempting to accomplish two things:
1)Minimizing resonant peaks in frequency response, and/or shifting the frequencies at which they occur so as to make them inaudible; and minimizing overshoot, ringing, time dispersive phase shifts, etc.
2)To the extent that those kinds of effects cannot be eliminated, making them as synergistic as possible with the sonic characteristics of the rest of the system.
It seems to me that all of the effects that come into play in item 1 would be reflected in the response of the system to a "square wave" with suitably chosen rise and fall times. And a methodology like that could conceivably facilitate item 2 as well, with the waveform characteristics providing clues as to what to listen for and what type of material to listen with.
Best regards,
-- Al
By "square wave" I did not mean to refer to something that is truly square, with edges that are nearly vertical, or that even approach being nearly vertical. My reference to "risetime and falltime corresponding to spectral components extending some distance into the ultrasonic region" means that the edges of the waveform would rise and fall in a controlled, somewhat gradual manner. Since risetime and falltime have an inverse relationship to bandwidth, if those parameters were set so as to correspond to a bandwidth of say 30 or 40kHz, and if the amplitude of the signal were small, I would not expect tracking to be much more difficult than for a high frequency low level sine wave.
The point to riaa pre-emphasis would be to make the waveform that is monitored on the scope, at the output of the phono stage or preamp, more readily interpretable by the user, given that the user would be monitoring at a point downstream from riaa de-emphasis. Monitoring the signal at the phono stage input, prior to riaa de-emphasis, may be problematic due to the low signal level, and possibly also due to the effect of probe capacitance on the signal being put out by the SUT.
I vaguely recall that such test records were available way back when, from Shure among others, but I have no knowledge of any that may be available now.
Scopes are very easy to use, btw, following some brief familiarization, and, as you are probably aware, are potentially useful for optimizing some tonearm settings as well.
Basically, as I see it, the process of optimizing SUT/cartridge loading is attempting to accomplish two things:
1)Minimizing resonant peaks in frequency response, and/or shifting the frequencies at which they occur so as to make them inaudible; and minimizing overshoot, ringing, time dispersive phase shifts, etc.
2)To the extent that those kinds of effects cannot be eliminated, making them as synergistic as possible with the sonic characteristics of the rest of the system.
It seems to me that all of the effects that come into play in item 1 would be reflected in the response of the system to a "square wave" with suitably chosen rise and fall times. And a methodology like that could conceivably facilitate item 2 as well, with the waveform characteristics providing clues as to what to listen for and what type of material to listen with.
Further developments are up to you!I'll keep it in mind. But if my Grace F9E Ruby performs as expected when I get it back from Soundsmith, I may not venture into mc's for a considerable number of years. :-)
Best regards,
-- Al