the science say that: better way for obtain a perfect stable rotation is perpetual ration mode.
The rotation should be disconnected fron any vibration induced from the motor drive.
The best way to approssimate this concept
we need have a heavy turntable low friction rotation and pulled from weak motor.
Is the exact opposite of light turntable with strong motor.
The rotation should be disconnected fron any vibration induced from the motor drive.
The best way to approssimate this concept
we need have a heavy turntable low friction rotation and pulled from weak motor.
Is the exact opposite of light turntable with strong motor.
Most possibly. I like the design, the approach and the performance of the old idler wheel Dual 1218, 1219 and 1229 turntables with their precisely gimballed arms, using two rings, a fixed outer one and an inner one that, in conjuction with the outer one, provides the horizontal movement and carries the ball bearings for the vertical movement as well. The WWW is full of drawings and pictures of these TT's and their arm gimbals.
Does someone by chance have plots like those in the previous posts of one or more of these three TT's?
Best regards!
Does someone by chance have plots like those in the previous posts of one or more of these three TT's?
Best regards!
Imo, yes. Slight amounts of vibrato and tremolo are euphonic.
A possible experiment: If you have a Bach WTC vinyl with Glenn Gould or Sviatoslav Richter. Listen through a very stable TT and through one with lesser rotational stability. If you do it, please post opinion on results
Thank you Lucky. We are waitingwill post results soon
It’s all over the net.
http://www.hificritic.com/uploads/2/8/8/0/28808909/classic-sc11-audible_effects_of_mechanical_resonances.pdf
http://www.theanalogdept.com/images/spp6_pics/TT_Design/MechanicalResonances.pdf
http://www.laudioexperience.fr/wp-content/uploads/2017/04/Bruel-Kjaer-Audible-Effects-of-Mechanical-Resonances-in-Turntables-AN17-233-1977-1.pdf
https://www.vinylengine.com/turntable_forum/viewtopic.php?t=1281
George
Hi Pano, here's the polar plot for that virtual file.Thanks Lucky for the explanation.
I've attached a virtual TT speed file below - zipped. Since I know exactly what's in it because I made it, it will be interesting to see what your polar plot makes of it. And also to see if I did it right.
Looks like a small amount of perfect eccentricity, and a twice per platter very short event that is beyond the display bandwidth of this tool to display properly, but I'd guess either a half sine or step change of duration of a few 10s mS.
When one thinks about it, unlike tape, record playback mechanically can't have significant FM bandwidth at any significant amplitude, because of mass of moving parts involved and available energy. And, not finding much FM above 40Hz in practice, that's where I put the tradeoff for bandwidth versus measurement resolution/noise for better or worse - it has a bandwidth of about 40Hz or so.
LD
Attachments
Looking at the amplitude spectrum of Pano's virtual TT file, it looks as though there's a realistic strong component at about 6Hz, perhaps intended to mimic the cart-arm resonance. However, this seems not to frequency modulate the 3150Hz test tone, so doesn't show up on the polar plot nor on a classic spectral plot.
Looking at the test tone waveform, that 6Hz component simply seems to be added (summed), and is neither AM nor FM which both requires some multiplicative element. So though it shows up in the classic amplitude spectrum, it doesn't modulate the test tone, whereas a real cart-arm system does. HTH, Pano !
LD
Looking at the test tone waveform, that 6Hz component simply seems to be added (summed), and is neither AM nor FM which both requires some multiplicative element. So though it shows up in the classic amplitude spectrum, it doesn't modulate the test tone, whereas a real cart-arm system does. HTH, Pano !
LD
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Thanks Lucky, that is exactly right. I made a tone that sweeps back and forth from 3147 to 3153 over 1.8 secs. Tried hard not to get glitches on the turn around, but they still show up in your plot. It's darn sensitive.
About the low tone. It's also a wobble, this time centered around 6Hz. You are correct that is was amplitude summed, I never could get it to frequency modulate the 3150 signal. That's OK, because it lets us know that it won't show up in your plot if it's just mixed in. I'll try again to modulate the 3150 signal at ~6 Hz and we'll see how that plots.
My virtual TT file also had some 60Hz and 41Hz mixed in, and a base of RIAA white noise to simulate surface noise. None of that showed up either.
About the low tone. It's also a wobble, this time centered around 6Hz. You are correct that is was amplitude summed, I never could get it to frequency modulate the 3150 signal. That's OK, because it lets us know that it won't show up in your plot if it's just mixed in. I'll try again to modulate the 3150 signal at ~6 Hz and we'll see how that plots.
My virtual TT file also had some 60Hz and 41Hz mixed in, and a base of RIAA white noise to simulate surface noise. None of that showed up either.
FM under the radar?
Guys,
FM caused by stylus scrubbing is characteristically encountered as a transient phenomenon, with the modulation hovering about the mass/compliance resonance frequency. This source of resonance excitation can be impulse disturbance such as footfalls, or transient variations in stylus drag friction that come from groove amplitude modulation transients in the program material. This, in turn, can excite horizontal and/or vertical arm resonance, which can manifest itself as FM, which can contribute to what is observed and measured as turntable ‘speed instability’.
I have not yet found a test disk that has tracks to simulate such a transient drag load on the stylus, but the absolute best test record I’ve acquired for demonstrating the audible effect of FM under steady state conditions is the ‘Ortofon Test Record’ #0001, and #0002, both sadly out of print eons ago. Tracks 8 and 9 on these records are a low frequency resonance test that consists of fixed 2349Hz and 2960Hz sinewaves superimposed with low frequency tones stepped through a range of 4Hz to 25Hz. FM effects are easy to hear when arm resonance is stimulated by such a continuous test tone. What distresses me in looking at all the wonderful research and analysis being posted here on this thread is that the source material being used for evaluating stability/instability effects is a steady state sinewave, typically 3150Hz, and the signal degradation from the transient effects that cause instability/FM seems to be slipping under the radar. I’m not surprised that significant AM and FM artifacts aren’t showing up in the polar plots when using a steady test tone, since steady state conditions don’t excite mass/compliance resonances. (Innocent reminder – low level FM looks like AM with only two sidebands.)
I submit that the reason that these expected FM artifacts (at multiples of the mass/compliance resonance frequency) aren’t showing up on the polar plots is that the test disk and “record player” DUT are actually pretty good. Pretty good, that is, under steady state conditions. A good turntable will move the 3150Hz in the groove past the stylus at a steady speed and the arm will be stable assuming a steady friction drag on the stylus. To simulate the transitory effect of FM you need either 1) a test record with a track that inflicts transient drag variation on the stylus to excite resonance or 2) a test record that contains a modulating low frequency tone that excites steady state resonance along with a medium frequency carrier tone that serves as ‘coal mine parakeet’ to enable us to observe and measure the FM, or 3) an idea that one of you might have that I hadn’t thought of yet.
The only currently available test record I know that meets the criteria in option #1 is the “HiFi News & Record Review Test LP – Producer’s Cut”. Side 2, Track 2 of this disk has a resonance test that contains a fixed 1000Hz sinewave superimposed with low frequency tones swept through a range of 5Hz to 25Hz. At resonance, a spectral analysis should show the 1000Hz carrier, and 1000Hz +/- integral multiples of the mass/compliance resonance frequency. Sorry, unable to provide a file clip of the HFNRR test track at this time. I’m technically incapacitated due to a recent move and home renovations, and all my stereo equipment including turntables are still boxed up from the move. Anyone else have this disk?
Cautionary note on the new ‘Ortofon Test Record’:
Ortofon’s new ‘re-issue’ does not include several of the test tracks that were on the 0001 and 0002 versions, including the most-valuable-for-our-purposes ‘Tonearm Resonance Tests’ which demonstrate the audible effects of FM so well. Versions 0001 and 0002 occasionally show up on fleeBay, but be wary that there is a 0003 version of the ‘Ortofon Test Record’ that is all music and does not have any test tones. Ask me how I know.
Well, I think I’ve hogged several post’s worth of material with this one…
OK, your turn.
Ray K
Guys,
FM caused by stylus scrubbing is characteristically encountered as a transient phenomenon, with the modulation hovering about the mass/compliance resonance frequency. This source of resonance excitation can be impulse disturbance such as footfalls, or transient variations in stylus drag friction that come from groove amplitude modulation transients in the program material. This, in turn, can excite horizontal and/or vertical arm resonance, which can manifest itself as FM, which can contribute to what is observed and measured as turntable ‘speed instability’.
I have not yet found a test disk that has tracks to simulate such a transient drag load on the stylus, but the absolute best test record I’ve acquired for demonstrating the audible effect of FM under steady state conditions is the ‘Ortofon Test Record’ #0001, and #0002, both sadly out of print eons ago. Tracks 8 and 9 on these records are a low frequency resonance test that consists of fixed 2349Hz and 2960Hz sinewaves superimposed with low frequency tones stepped through a range of 4Hz to 25Hz. FM effects are easy to hear when arm resonance is stimulated by such a continuous test tone. What distresses me in looking at all the wonderful research and analysis being posted here on this thread is that the source material being used for evaluating stability/instability effects is a steady state sinewave, typically 3150Hz, and the signal degradation from the transient effects that cause instability/FM seems to be slipping under the radar. I’m not surprised that significant AM and FM artifacts aren’t showing up in the polar plots when using a steady test tone, since steady state conditions don’t excite mass/compliance resonances. (Innocent reminder – low level FM looks like AM with only two sidebands.)
I submit that the reason that these expected FM artifacts (at multiples of the mass/compliance resonance frequency) aren’t showing up on the polar plots is that the test disk and “record player” DUT are actually pretty good. Pretty good, that is, under steady state conditions. A good turntable will move the 3150Hz in the groove past the stylus at a steady speed and the arm will be stable assuming a steady friction drag on the stylus. To simulate the transitory effect of FM you need either 1) a test record with a track that inflicts transient drag variation on the stylus to excite resonance or 2) a test record that contains a modulating low frequency tone that excites steady state resonance along with a medium frequency carrier tone that serves as ‘coal mine parakeet’ to enable us to observe and measure the FM, or 3) an idea that one of you might have that I hadn’t thought of yet.
The only currently available test record I know that meets the criteria in option #1 is the “HiFi News & Record Review Test LP – Producer’s Cut”. Side 2, Track 2 of this disk has a resonance test that contains a fixed 1000Hz sinewave superimposed with low frequency tones swept through a range of 5Hz to 25Hz. At resonance, a spectral analysis should show the 1000Hz carrier, and 1000Hz +/- integral multiples of the mass/compliance resonance frequency. Sorry, unable to provide a file clip of the HFNRR test track at this time. I’m technically incapacitated due to a recent move and home renovations, and all my stereo equipment including turntables are still boxed up from the move.
Anyone else have this disk? Cautionary note on the new ‘Ortofon Test Record’:
Ortofon’s new ‘re-issue’ does not include several of the test tracks that were on the 0001 and 0002 versions, including the most-valuable-for-our-purposes ‘Tonearm Resonance Tests’ which demonstrate the audible effects of FM so well. Versions 0001 and 0002 occasionally show up on fleeBay, but be wary that there is a 0003 version of the ‘Ortofon Test Record’ that is all music and does not have any test tones. Ask me how I know.
Well, I think I’ve hogged several post’s worth of material with this one…
OK, your turn.
Ray K
Hi Ray.
Thanks for the post.
I have this test disk.
One day I’ll do a recording of this track .
George
The first file is the one Ray asked.
All recordings through a JVC QL-A2 turntable with Shure M97xE at 1.5gr VTF (brush locked in up position)
Ambient temp. 30.7d. Celcius
Rel. humidity 38%
1 HFN S2 T2 Cartridge-Arm Lateral resonance test (sweep).wav
https://www.dropbox.com/s/qaj9xte0ji0y1ah/1%20JVC%20QL-A2%20%2B%20Shure%20M97xE%201.5gr%20HFN%20S2%20T2%20Cartridge-Arm%20Lateral%20resonance%20test%20%28sweep%29.wav?dl=0
2 HFN S2 T3 Cartridge Arm Vertical resonance test (sweep).wav
https://www.dropbox.com/s/x1ckrdazd40qtn9/2%20JVC%202%20QL-A2%20%2B%20Shure%20M97xE%201.5gr%20HFN%20S2%20T3%20Cartridge%20Arm%20Vertical%20resonance%20test%20%28sweep%29.wav?dl=0
3 HFN S2 T6 unmodulated groove.wav
https://www.dropbox.com/s/kljgj9iqssw6ssc/3%20JVC%20QL-A2%20%2B%20Shure%20M97xE%201.5gr%20HFN%20S2%20T6%20unmodulated%20groove.wav?dl=0
4 HFN S1 T6 300Hz +12dB.wav
https://www.dropbox.com/s/nwpeff21bnyint7/4%20JVC%20QL-A2%20%2B%20Shure%20M97xE%201.5gr%20HFN%20S1%20T6%20300Hz%20%2B12dB.wav?dl=0
George
All recordings through a JVC QL-A2 turntable with Shure M97xE at 1.5gr VTF (brush locked in up position)
Ambient temp. 30.7d. Celcius
Rel. humidity 38%
1 HFN S2 T2 Cartridge-Arm Lateral resonance test (sweep).wav
https://www.dropbox.com/s/qaj9xte0ji0y1ah/1%20JVC%20QL-A2%20%2B%20Shure%20M97xE%201.5gr%20HFN%20S2%20T2%20Cartridge-Arm%20Lateral%20resonance%20test%20%28sweep%29.wav?dl=0
2 HFN S2 T3 Cartridge Arm Vertical resonance test (sweep).wav
https://www.dropbox.com/s/x1ckrdazd40qtn9/2%20JVC%202%20QL-A2%20%2B%20Shure%20M97xE%201.5gr%20HFN%20S2%20T3%20Cartridge%20Arm%20Vertical%20resonance%20test%20%28sweep%29.wav?dl=0
3 HFN S2 T6 unmodulated groove.wav
https://www.dropbox.com/s/kljgj9iqssw6ssc/3%20JVC%20QL-A2%20%2B%20Shure%20M97xE%201.5gr%20HFN%20S2%20T6%20unmodulated%20groove.wav?dl=0
4 HFN S1 T6 300Hz +12dB.wav
https://www.dropbox.com/s/nwpeff21bnyint7/4%20JVC%20QL-A2%20%2B%20Shure%20M97xE%201.5gr%20HFN%20S1%20T6%20300Hz%20%2B12dB.wav?dl=0
George
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