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In Reply to: RE: Some test records comparisons posted by Thomas_A on July 09, 2017 at 00:50:39
Interesting results. I have the original Ortofon Test Disc TC002 as well as the latest release and the other discs you mentioned (although the re-released version of HFNRR) along with the CBS test discs. I was disappointed that the re-release version of the Ortofon lacked the white noise test for the channel phasing test - very useful for frequency response tests in vertical and horizontal modulation.
With respect to the variability in the channel separation results, some of that has to do with the pressing uniformity of the disc. If you did a slice through the spindle, you may find that the disc actually gets slightly thicker towards the spindle so there is an inherent "azimuth error" due to the variation in the record thickness. Also, errors in antiskate, HTA and SRA can also induce some variability in the tracking ability tests and vertical modulation channel balance.
Incidentally, with your loading experiment for the V15Vx, that's a pretty extreme change to Shure's original loading!
This is the M97/SAS loaded at 47k and 130pF using white noise. With the stock stylus, it is ruler flat from 10kHz to 23kHz, but the gentle tilt from 1kHz to 10kHz is an inherent part of the Shure "audiophile curve". I actually prefer the stock stylus tonal balance to the SAS (although the SAS is superior in every other way!) with classical and jazz.
How did you convert the pink noise back to a flat characteristic to determine the frequency response?
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Follow Ups:
"How did you convert the pink noise back to a flat characteristic to determine the frequency response?"Voxengo's latest "SPAN" VST3 free plugin has a control for changing the slope of the displayed output. It would be very easy, using this plugin, to add a +3dB per octave slope compensation to a pink noise capture.
I've been very impressed with the latest release. Nitpicks are: I'd love if had options for using bigger bins, say 2^20 samples, so there could be more confidence in the results down around cart/arm resonant frequency. Also still seems lacking options for different windowing. I've been using it more lately and it seems pretty good.
Edits: 07/11/17 07/11/17
Thanks for that! I didn't know about Voxengo and was interested in some of their modules which would be a useful addition to what I currently have with RX Advanced and SoundForge.
Have you gone for the "Premium Membership" option?
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
I don't know if I could justify the Premium Membership but they sure do have some interesting looking toys.
I almost went for CurveEQ just because I thought it was cool. I don't really know what I'd use it for.
I was ready to pay for bigger FFT block size if the plus version of SPAN offered that. It also maxes at 2^16 blocks.
I'm trying to figure out how to give them money....They made their free SPAN too nice.
Thanks, interesting as well. What is the slope in dB from 1 to 10 kHz? The unusual load that was tested to get a target response of ca +/- 0.5 dB between 1-10 kHz, and the drawback is the sloping response above 13-14 kHz.
To use the pink noise, I export the values from a FFT and then convert to "linear" by adding 3 dB per octave. Formula from 1000 Hz: dBcorrected=dBmeasured+3*ln(fmeasured/1000)/ln2
This is the response with the stock stylus, but with a reduced FFT size compared to the other one and you can see how flat the response is above 10kHz. However, it suggests nearly a 4dB difference between 1kHz and 10kHz. I am away from my workstation, so can't zoom in for the detail. Shure were obviously trying to achieve something like a "pink" response characteristic. I still prefer the V15TypeV balance although the story goes that it was criticised for sounding too much like CD so they modified the response (Audiophile Curve) to satisfy those who wanted a warmer sound. With the right material I think it is successful, but can sound a little ponderous and bass heavy with some recordings.
Although for my transcriptions I demand a cartridge with the flattest characteristic for the entire passband, for general listening I actually keep the default loading and accept the "flavour" that the manufacturer was aiming for. As you demonstrated, there is always a tradeoff with bandwidth vs uniformity and I like to think the manufacturer/designers knew what they were doing! These days, MM cartridges (and some MCs) appear to be specifically voiced and the manufacturers don't seem to pay so much attention to uniformity of the response. I have a V15TypeV with a SAS and the response is considerably flatter and very extended with a very subtle dip centred around 10.2kHz. This is nicely flattened out with a +1.5dB gain (Q=1.2) at 10.2kHz. I wasn't enamoured with the 12kHz "lump" that JICO introduced for the "audiophile curve" styli and think that the stock stylus was a better balance in comparison!
"To use the pink noise, I export the values from a FFT and then convert to "linear" by adding 3 dB per octave. Formula from 1000 Hz: dBcorrected=dBmeasured+3*ln(fmeasured/1000)/ln2"
Ah, that would have been rather tedious! I thought you were using a plugin! Personally I don't understand why they put Pink noise tests on the test discs in the first place. Most people would be using it to test frequency response uniformity of the cartridge itself and broadband channel separation, I would have thought, rather testing for subjective balance.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
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