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In Reply to: RE: Anyone know where to find out the cartridge 'rise time'? posted by John Elison on October 21, 2014 at 20:56:49
John,
Would the MM vs MC rise time differences also be related to the differences in material used for the transducer (magnet vs coil)? i.e. lower mass coil have less mass, therefore less inertia, and react to the vinyl grooves faster?
-Theron Day
Follow Ups:
It is certainly true that the mass of materials used in the cantilever moving system will place limits on the upper cutoff frequency of any cartridge. However, modern MM cartridges have no greater moving mass than modern MC cartridges. In fact, the cartridge with the lowest effective tip mass ever measured was a Technics MM cartridge. Therefore, it is my opinion that high coil inductance in MM cartridges is responsible for their bandwidth limitation rather than moving mass.
The mass of the moving parts of most cartridges will limit their upper frequency cutoff to around 50-kHz to 70-kHz and this is true for both MC and MM cartridges with reasonably low effective tip mass. However, nearly all MM cartridges have bandwidths less than 25-kHz as a result of their high inductance coils reacting with wiring capacitance to form an electrical resonance in the neighborhood of 15-kHz to 20-kHz. Low-output moving coils, on the other hand, have their electrical resonance in the neighborhood of 1-MHz to 2-MHz, which is well above any mechanical limiting factors. This allows low-output moving coils to have greater bandwidths and faster rise-times than high-inductance MM cartridges.
Best regards,
John Elison
Where does your info come from since AFAIK you haven't measured an mm in years and haven't used one in decades. I posted specs for a few mm's but you ignore them even though some Vinyl inmates use the carts listed, including me. So how did you conclude that "nearly all" mm's have bandwidth less than 25kHz?
Grado Master Reference: 10Hz - 60kHz (Statement series go to 75kHz)
AT ML170: 5Hz - 40 kHz
Ortofon 2M Black: 20Hz-31kHz
AT150mlx: 10Hz-30kHz
ADC XLM: 15Hz-24kHz
Grace F9 - according to Vinyl Engine above 60kHz
Music Hall Mojo: 20Hz-27kHz
Nagaoka MP-500: 20Hz-25kHz
Pickering XSV 3000: 10Hz-30Khz
Soundsmith Zephyr 15Hz-45Khz - interesting that SS's top carts only go to 20Khz.
> So how did you conclude that "nearly all" mm's have bandwidth less than 25kHz?
It is easy to conclude from calculating the resonance frequency of the tank circuit formed by coil inductance and wiring capacitance. If you measure all those cartridges you will undoubtedly find that their high-frequency response is down below -3-dB at frequencies above 20-kHz or so. It is my experience that most MM cartridges' frequency response falls off quite rapidly above 20-kHz. The problem is that only rarely do manufacturers provide frequency plots that go beyond 20-kHz and never do they specify the decibel limits of their stated frequency response. Therefore, their stated frequency response is often meaningless.
Best regards,
John Elison
The mechanical resonance of many designs does permit a response to extend well past 25kHz before the cutoff is reached. Ignoring low impedance MM designs like Stanton/Pickering's XLZ/LZS models, CD4 replay was all done with MM cartridges back in the day. The key being that the load resistance was set at 100k in order to utilise the mechanical resonance peak to be able to get a good response of the carrier at 30kHz.
However, even into the "standard" load, the replay response of the Stanton CS100 quotes confidence limits of ±1dB between 20Hz to 20kHz and they claim a response out to 50kHz. The inductance for this cartridge is 270mH which puts the electrical resonance at around 18.5kHz into a standard 47k load, with 275pF.
My best example to use would be a Stanton 681 which has an inductance of 930mH which would gives an electrical resonance of 10kHz. The damping factor of this design is somewhat higher at 0.62 than the usual 0.5 or less of most common designs. However, the response extends past 25kHz to 29kHz (on the vertical modulation test track) on this particularly poor sample of a EEEMkIII stylus which was way out of spec for compliance - I suspect this may have been a DJ stylus with the wrong labelling based on the VTF required to get acceptable tracking!
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
What test record are you using? Since you're using a Spectrum Analyzer, you must be looking at pink noise or some kind of noise spectrum. Am I correct? That is very interesting, though. I guess the drop at 30-kHz is where the noise ends. Do you think that most MM cartridges have extended frequency response? The Shure V15VxMR that I bought several years ago seemed to start drooping in the upper frequencies with a definite downward turn after its calculated electrical resonance of 15.4-kHz.
Thanks,
John Elison
I used the white noise response that is part of the phasing test on the Ortofon Test Disc. There is a lateral cut with a bandwidth of 23kHz and a vertical cut with a bandwidth of 29kHz - I don't quite understand why there is the discrepancy! I also have the CBS test disc STR-112 that you used for the square wave tests of your Shure V15 plus HFNRR test disc and the Analogue Productions Ultimate test LP. Of them all, I prefer the Ortofon as the most versatile. For me a pink noise test is a nuisance as, like you, I don't have a good phono amp with switchable EQ. I have verified the EQ accuracy of my phono stage with an inverse RIAA network so I'm comfortable with the accuracy of the Ortofon cut. The HFNRR disc is not as accurate I believe (based on the pink noise response characteristic) - I originally just used it for the +16dB and +18dB tones and the broadband channel separation measurements. This is mainly because I don't think much of The Exchange cutting engineers and don't trust their ability to make a high quality/accurate cut based on my experience with their commercial work.
To answer your question, putting the Shure "x" modified response bodies aside, yes, I think that a "good" (high impedance) MM design can extend the response beyond 20kHz quite easily. The issue I feel is the quality and uniformity. Given the target price point for the majority of MM designs, most designs available today have a rather higher tip mass than is ideal and the mechanical resonance is also not as high as a good MC. Based on my white noise meansurements, most of my mid price MM designs have a mechanical resonance in the range 20 to 28kHz (at a guess). On that basis, I would have to agree with your previous posts on the subject that low output MC or low impedance MM is the way to go to put the electrical phase shift as high as possible. Although the Stanton LZS claims to be designed for a 100ohm input resistance, this puts the cutoff at 16kHz and a 5dB loss at around 18kHz. When this is corrected by increasing the input resistance to 2k, this design does show off MC like qualities in the treble region. The FR is absolutely ruler flat up to 10kHz before a slight 2.8dB dip at 18kHz then rising gently above 20kHz towards the mechanical resonance (the response at 29kHz is some +5dB above the 1kHz reference level). This has proven to my satisfaction that a good MM can be passed off as a MC.
The Shure "x" bodies are curious in that the pseudo pink-noise like rolloff was deliberately engineered. I don't know what they did with the magnetic circuit to achieve the response, but my M97xE does actually have a ruler flat response from 10 to 23kHz whilst following the same general trend you show from 1kHz to 10kHz. The inductance is 650mH giving a resonance at ~12.1kHz and the damping factor is 0.52 (275pF load).
Apart from the poor quality of the cantilever alignment and the woeful tracking that doesn't meet specification.....It does make reasonably pleasing noises, but can't compare to my OC9 or Denon DL301!
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Well, it looks like you're right and I'm wrong about the extended frequency response of MM cartridges. I think the Shure "x" bodies do not have laminated cores and perhaps that is responsible for their attenuated high-frequency response. However, I've been conducting frequency response tests for more than 40-years and all the old MM cartridges like Pickering, Empire, Stanton, etc. seemed to have pretty steep attenuation after 20-kHz. I switched to moving coils nearly 40 years ago primarily because of the way they sounded, but when I started measuring them I found they had extended high-frequency response. Now, I can't hear past 12 or 13-kHz, but MC cartridges still sound better to me than a Shure V15VxMR. ;-)
Do you have any test records with spot frequencies and/or sweep frequencies? I've kind of lost interest in making measurements, but I always wanted to find a software based chard recorder that could run a frequency response curve from a digitally recorded sweep. I now have the capability to record these sweeps at 24/192 or even DSD128. Furthermore, I have saved all my previous 24/96 digital copies of test signal recordings from the past 10-years and I specifically recorded RIAA frequency sweeps just in case I ever found the appropriate software. You would think that someone would have produced some inexpensive or even free software that can replicate a chart recorder on a computer screen, but I've never found anything that I could afford.
The problem with your white noise measurements is that they seem to slope downward by about 10-dB from 100-Hz to 20-kHz. Do you know what causes that? It would be great if you could process a frequency response curve from a frequency sweep. I've got test records with constant velocity sweeps that run from 1-kHz to 50-kHz. They need to be played without RIAA equalization, perhaps through a microphone preamp. It would be interesting to be able process these sweeps into frequency response curves.
Best regards,
John Elison
This is an interesting point you raise. As you noted, the white noise response is not a true representation of the actual transducer response. I should actually be establishing the transfer function with respect to the input signal. However,the difficulty is in getting an accurate transfer function for the RIAA stage and also knowing for certain that the cutting process is truly uniform in order to know for sure that I have the actual transducer response. The other limitation is in the duration of the test tone to have a sufficiently large number of occurrences for each frequency component. Given these limitations, I use the white noise response a little differently - I have a chosen reference response and map differences of other cartridges back to the reference.
I do also have the CBS STR-100 test disc, but haven't been motivated to use this as my present method seems to give me the result that I'm after which is a mapping relationship.
The observation you made regarding the attenuation characteristic mainly applies below 1kHz and is dependent on the number of points chosen for the FFT as well as LF resonances due to arm/plinth and cantilever suspension interactions. I admit that I haven't been particularly consistent in the number of points chosen for my screenshots. Beyond 1kHz, the response is reasonably representative of the transducer response - I attach a trace for my AT-OC9 which I think you will agree is essentially uniform above 1kHz. This is my reference response for mid to HF uniformity - although I use iZotope RX for my main processing, like you, I use Soundforge to zoom in and get more accurate amplitude information to plot out relative amplitude. I then use the relative differences to digitally equalise my recordings (FIR to achieve linear phase) from all other (MM) cartridges to match the OC9 response. Generally I only need to apply EQ above 8kHz and I have been very pleased with the accuracy of the results which successfully minimise the tonal differences due to frequency response variations. Of course detail retrieval etc is still highly dependent on stylus profile/condition and arm matching, so one can still "hear" a better design. I still believe that the dominant effect on sound quality is related to stylus profile and alignment in the cantilever (laterally as well as SRA) combined with cantilever materials and the accuracy of the tracking angle more than the transducer principle. I guess that's pretty much a cartridge as a whole isn't it? ;)
Incidentally, I note that you mention your new recording capability with DSD - what is your new ADC? I'm still using a Benchmark ADC1-USB which is limited to 24/96 through USB. However, I have actually settled on 24/88.2 for two reasons; The first was technical, I eliminated problems with dropped samples and glitches (even using ASIO and a fast SSD), the second was a subjective improvement in SRC when down converting to 16/44.1 for creating CDs that my mother could enjoy. Good as iZotope's SRC is, I still feel that integer downsampling is preferable subjectively.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
Hi Anthony,
I have been recording with an Alesis Masterlink for 10-years, which has a maximum resolution of 24/96. I used to have Sound Forge 7 software with a spectrum analyzer, but my computer crashed and I no longer have the Sound Forge software. Like you, I always copied LPs at 24/88 for down-sampling to 16/44 but I used 24/96 for all my measurements.
Last month I decided I needed a new digital recorder and TASCAM was offering a $200 mail-in rebate on their DA-3000 so I bought one. It can record PCM up to 24/192 and DSD up to DSD128 (5.6-MHz). I'm still learning how to use it and I need to find some computer software for mastering because the DA-3000 is strictly a recorder. I kind of miss the mastering capability of the Masterlink, but the removable memory cards in the DA-3000 makes it much easier to transfer recordings to my computer. It can record on SDHC and CF memory cards, and it accepts a USB flash drive for playback only, which allows me to play DSD files from other sources. It also has an input level control so I no longer need to normalize my recordings like I did with the Masterlink. It sounds very good, too. I've been using it for playing DSD files and I really like the sound of DSD.
Best regards,
John Elison
Hi John
Thanks for the info on the Tascam unit! It looks a well thought out design - I had been looking at options but didn't know about this one. The ability to record to a memory card is rather attractive as I'm no longer bound by interface limitations or interface driver issues.
For mastering I use iZotope RX3 advanced (as a standalone application). I also have the latest SoundForge Audio Mastering suite which combines the Sony equivalent of RX3 with Soundforge. To be honest I haven't used it except for recording and pre-processing (to remove DC offset etc) before moving to RX3 which I find gives me more control and is somewhat faster. It also comes bundled with iZotope SRC and MBIT+ dither modules plus a lite version of iZotope Ozone. Again I haven' any use for that product as I just want to clean up clicks and equalise the cartridge response. Beyond that I simply want a facsimile of the LP!
If you still have the license code for Soundforge 7, you could probably get a discount for an upgrade. Sony seem to continuously be offering discounts!
The declick algorithms in RX3 are somewhat more effective and offer slightly greater flexibility than Soundforge's native algorithm and the proprietary iZotope SRC and MBIT+ dither modules are very transparent when set "appropriately".
One warning though - RX3 does benefit greatly from a fast processor. I built a workstation around an i7-4770k and this just gives me ~2x real time when doing more advanced processing in RX3.
Regards Anthony
"Beauty is Truth, Truth Beauty.." Keats
not that the London is ruler flat, but goes out to 24 khz with realistic loads and he has some 1 khz square wave measurements...which are really interesting :)
dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
Thanks, Dee. I wish Stereophile still conducted measurements like that.
I have the STR-112 test record and I've looked at the square wave performance of the Shure V15VxMR that I bought 10-years ago. My problem is that I don't have a high quality phono stage without RIAA equalization. I believe I used the amplifier in a two channel AC milivoltmeter to amplify the cartridge signal for the following square waves. The test record contains both laterally modulated and vertically modulated square waves on outer and inner grooves. I looked at the Shure V15VxMR with different loads.
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if i had that record and wanted use it. Most likely a mic amp that can be used for ribbon microphones. Those would have the highest gain and the widest bandwidth. A used pro mic amp can be had for not much money. Also it just has to measure well :)dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
Edits: 10/23/14
Thanks, Dee. I thought of that, but I just haven't gotten around to it. My interest in measuring phono cartridges has diminished over the years.
Best regards,
John Elison
just thought i throw it in as a cheap option i have seen then as low as 30 bucks without the phantom supply.
dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
Have you calculated "the resonance frequency of the tank circuit formed by coil inductance and wiring capacitance" for any of 'em?
Yes, I've calculated it for a number of moving magnet cartridges. All the ones I calculated had electrical resonance frequencies between 15-kHz and 20-kHz. You can do it yourself. Here's the formula.
Which ones? Apparently none of the mm's I listed, all of which have claimed FR of 25kHz and above ('cept one that goes to 24kHz).
It's real easy, Rick. If you have the values for coil inductance you can estimate wiring and phono stage capacitance at 250-pF. Just plug the numbers into the formula. You must have a calculator. If not, use a spreadsheet. It's easy.
Good luck,
John Elison
I look forward to your FR graphs for the carts I listed. No doubt you'll have 'em ready before your next blanket statement about mm's :-)
This is the plot in the (small) booklet for the JVC X-1 CD-4/Shibata.
Same JVC TRS-1005 disc (traces dated 18 Oct 1974...)....just remembered: have another piccie showing 'the works'
Edits: 10/22/14
The cartridge must go out further than the graphs show. The sharp drop off is the measurement method. Roll off of a device like that would always be much slower.
end at 20 KHZ. i do not know if the extended measurements were done with actual records or they used a mechanical transducer to excite the stylus.
dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
here is one MM that seems to do ok :)
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
Yeah, that's the Technics MM cartridge with the lowest effective tip mass ever measured and I believe it also has very low inductance and low output. I'm sure its not flat to 100-kHz, though. It is probably down considerably at that point.
mot even an EPC 100 mk 4 just a 205....but there is an exception to every rule...
dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
but the internal resonances, and damping characteristics will effect what happens at the end of the rise. Phase shifts and etc will have various effects.
So even if you have two cartridges with the exact same bandwidth you may not have the same square wave response for them. I am trying to find any references on measuring square wave responses for LPs, but can't. Here is a good treatise on cartridge measurements
dee
;-D
True terror is to wake up one morning and discover that your high school class is running the country.
quote by Kurt Vonnegut
Decades ago Hi Fi Choice did do 1 KHz square waves. I have an issue testing at least 50 pickups. But as I recall they stopped this in later issues.
nt
-Theron Day
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