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Objective measurements of phono cartridges

Discussion in 'Analog Audio Forum (amplifiers, cables, etc.)' started by jhaider, Sep 19, 2017.

  1. TBone

    TBone Addicted to Fun and Learning

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    ... no digital intervention (DSP) is used with my rips. Prefer the straight goods, so to speak, because I often share my rips with others as to give an indication of my analog systems prowess and or the specific LPs mastering quality. In other words ... they have nowhere to hide from all the so called evils of analog, yet ...
     
  2. Blumlein 88

    Blumlein 88 Major Contributor

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    Well, you might want to try half speed recording if your TT will do it. It can be a benefit. The only DSP is simply doubling speed once you are done. If nothing else, surely you would be a little curious the difference that could make for something so simple to try on a disc or two.
     
  3. Don Hills

    Don Hills Senior Member

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    There is no free lunch. You need to re-equalise as well as double the speed. You also have the problem that tonearm and other resonances effectively double in frequency and may become more audible. It makes it much harder to apply "rumble" filtering.
     
  4. TBone

    TBone Addicted to Fun and Learning

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    Thanks but not interested in that kind of so called improvement ... rather my goal was more within TT design, to control and or eliminate noise and speed variations, resonances, trust me .... much harder said than done. I`ve learned so much lately ... but it`s been a frustrating journey with this particular turntable, to say the least. However, I can safely say that those goals have now been mostly realized (using new apps on a cell phone have helped considerably), and not surprisingly, my latest rips are easily some of my very best. I think I`ve finally got the most out of this particular turntable (yes, much science exist behind the making of a great turntable) ... but I`m eager to move to another TT which I had in the wings near forever which potentially should sound as good or better (less noise, less overall compliance) without nearly all the hassles.

    Funny, I mention to any analog nut within shouting distance that I try to setup and make my turntable sound more like a great CD player than a traditional turntable ... and they generally cringe ... until they hear the results.

    When I have the time, I will forward you a copy of one of my latest rips.
     
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  5. Arnold Krueger

    Arnold Krueger Member

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    Facilities and procedures for doing this correctly can be found in the Audacity audio editor (freeware) and its online documentation. They have built speed-adjustable RIAA and inverse RIAA filters into their product.

    One mitigating factor is that it is fairly common for LPs to have a fairly significant bass roll-off applied to them during mastering to facilitate LPs being played on low performance players.

    I know of one label that had a company standard based on an 85 Hz fourth order high pass filter implemented in the consoles used for tracking. They never intended to produce anything with content below that frequency, knowing what sort of gear it was likely to be played on. They baked the 85 Hz roll off into their product that close to the original performance. They wrote arrangements that took it into account. This continued until they realized that shortly, most of their product would be sold on CDs.

    While 85 Hz was probably extreme, this sort of thing maybe shifted down an octave, was not uncommon. With tone arm resonances being around 10 Hz, the half speed recording technique would raise them at 20 Hz which is stll managable as long as you can tolerate a 30 Hz filter.

    There are other less intrusive ways to address this problem which I hope to test before I publicize them.
     
  6. Blumlein 88

    Blumlein 88 Major Contributor

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    I have done it a few times. Low rumble is also lower in frequency at lower speed (or at least never reared its head as a problem). I handled the RIAA by doubling speed then doing RIAA. I also used a 30 hz roll off. Wasn't it the IHF that used to recommend that 30 hz cut in RIAA curves? I remember having an optional button for that on gear back when.

    Here are some additional Audacity curves for various purposes (33 as well as 45 and 78 rpm) ( I see Arny has beat me to it).
    http://wiki.audacityteam.org/wiki/78rpm_playback_curves#EQ_Curves_Library

    Haven't done much of this recently. I do remember if a TT had tonearm resonances that were obvious I notched them out enough to reduce that. As always used as little as I could get away with. Not trying for perfect, but a big resonance at 10 or 12 hz didn't seem desirable.

    Now I never did find noise reduction techniques I was happy with. Some were not too bad and if a record was very, very noisy it might be worth doing.
     
  7. Don Hills

    Don Hills Senior Member

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    Thanks. How about the result? Was there enough of an improvement to make it worth the effort?
     
  8. Blumlein 88

    Blumlein 88 Major Contributor

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    I thought there was a solid though not huge improvement. The improvement was greater if the record was in good shape, not worn, dirty or noisy.
     
  9. Don Hills

    Don Hills Senior Member

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    Thanks. I'm slowly getting ready to rip those albums in my collection that don't have digital alternatives.
     
  10. Fitzcaraldo215

    Fitzcaraldo215 Addicted to Fun and Learning

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    Wow, I am surprised that vinyl disc remasterings are not released in 66-2/3 RPM pressings, the analog equivalent of digital hirez. Ah, I get it. Vinyl is so outstandingly marvelous already that it could not benefit from any increased resolution.

    But, seriously, in my vinyl days of yore, it was probably true that the few audiophile 45RPM remasters sounded pretty good, either from the remastering, the higher RPMs or all of the above. But, did they deliver unforgettable audio nirvana, all things considered? Definitely not.

    Nontheless, I see your point, which is very interesting and clever, although I also wonder about the RIAA EQ curve considerations already questioned by others. I think that a custom double-speed RIAA curve would need to be introduced in DSP on top of the RIAA EQ already applied by the phono preamp. That might be tricky.
     
  11. svart-hvitt

    svart-hvitt Active Member

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    There are some neutral phono preamps, aimed at digitalization.
     
  12. Fitzcaraldo215

    Fitzcaraldo215 Addicted to Fun and Learning

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    No doubt, but the double speed idea is still a problem, unless those phono preamps are specifically designed for playback at higher speeds.

    If there is, say, a 100Hz tone on a 33.33 RPM record, its level has been mastered on the disc by the RIAA curve value for 100Hz. No problem, because the inverse RIAA curve in the phono preamp reeq's that tone to flat at 100 Hz. And, of course, the amount of RIAA boost/cut on the disc varies considerably as a function of frequency.

    If it were played back at 66.67RPM, that same tone is now seen as 200Hz by the phono preamp. So, the inverse RIAA in the normal phono preamp curve applies the wrong level EQ correction for the signal on the disc - the one at 200Hz rather than 100Hz. Etc., etc.

    Also, one should be sure that the phono cartridge and preamp can cleanly handle 40k Hz, which would be double 20k.

    I don't know. I have not touched an LP in well over a decade or even thought much about ripping my thousands of LPs. As I said, just using a regular phono preamp would not work for this. Perhaps all these ideas are already incorporated in some sort of digital phono preamp with suitable adjustments to the RIAA curve for higher than normal speeds. Either that or a complex digital EQ curve needs to be applied additively to the normal phono preamp output. Actually, 45RPM ripping of 33RPM LPs would probably be a better idea, since 45 is commonly available and 66.67 is not.

    The other cool thing about this idea is that the ripping time per LP is substantially reduced.
     
  13. Don Hills

    Don Hills Senior Member

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    What svart-hvitt meant was that there are phono preamps with no RIAA equalisation, designed for direct input to an ADC so that RIAA and other equalisation can be applied by DSP.
    Cartridges run close to the limits tracking HF at normal speed. Increasing the speed would make tracking worse.
     
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  14. Blumlein 88

    Blumlein 88 Major Contributor

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    I noticed something else perhaps muddying the waters. You can rip an LP by feeding the output of a phono preamp to an ADC. If you did that at half speed, then yes getting correct RIAA is problematic. So do that at normal speed.

    What I had in mind is when you feed the direct cartridge signal to a microphone preamp which then gets digitized. No EQ has been done and you can record it at any speed, fix the speed later and then do RIAA EQ once you have it at normal speed. The issue with this approach is most cartridges like to see an input impedance of the phono stage of 47 kohm, and most microphone pre's are much lower than this. I once made a box to correct for that between cartridge and microphone pre input. Some microphone pre's have an input pad which as well as reducing input level raise the impedance (sometimes to 25 kohm) which can make the cartridge work close enough to okay depending upon the cartridge.

    Like most things if you look closely enough things get complicated.

    I suppose thinking about it you could play a disk at reduced speed going thru a phono preamp. Then reverse the RIAA curve digitally. This gives you something close to a flat un-EQ'd result. Then speed it up to normal. Finally re-apply RIAA EQ and get a proper result. If your phono stage is accurate enough it should work. Last time I messed about with them I found most phono stages surprisingly good on the RIAA curve. Like +/- .25 db good.

    I suddenly seem to remember why I am happy not to have an LP rig or LP collection anymore.
     
  15. TBone

    TBone Addicted to Fun and Learning

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    full speed, half speed, warp speed ... none are real world turntable issues ... the real trick to reducing vinyl "noise" obviously starts at it's source; album cleaning & precise cart setup, however, IME, the turntable itself represents the biggest key in limiting noise (it is extremely difficult to design turntables without introducing noise, at any cost).

    I've found that the quieter the turntable becomes in operation, the more resolving it becomes, but ... often exposing other issues related to your system, and especially quality of the LP itself. This is why, often on demonstration, better turntables appear to sound less appealing to many listeners, even very experienced listeners ... when compared to lesser (noisier) tables which tend to "hide" other issues while often providing more apparent bass. In my travels, more often than not, on initial listen, the listener often prefers the noisier 'table on first demonstration.

    Better (less induced noise) turntables effectively attenuate vinyl noise to a large degree, but what's really happening is that they don't further amp&modulate noise further into the mix. Turntable noise comes in many forms ... but generally ... the quieter 'tables provide a change in sonic perception, a change in sonic character, in that (again, generally speaking) Bass seemingly becomes less apparent overall, compared to a turntable with more introduced internal noise. (I've done this test on the same turntable many times over) In actuality, the perception of more bass is a false positive ... accurate bass starts & stops much faster with greater (and more realistic) initial impact, but appears less "there" overall.

    Dallas Justice has repeated stated that he considers Bass reproduction a major problem with many turntables (and esp tonearms), which is true ... but it's certainly not a blanket statement born of any realistic truth ... the real truth is based on his particular turntable/arm of choice, his setup (issues obvious to me when viewing the text & pictures he provided on his wbf posting concerning the very subject matter at hand).

    sidebar...
    Strangely enough, the near exact same effect occurs but to a lesser degree (more perceived bass) with the addition of more solder-joints, pots, connections, switches, wires added to a pre-amp section. I can still remember, after a relatively recent pre-amp mod (changed the passive "direct" path of electronics) I immediately noticed seemingly less bass ... when testing on a friend who is very experienced with my system (without any knowledge of any mod) ... his first reaction to the session was "where did the Bass go?".

    I found his reaction particularly interesting because it mirrored mine on first impression ...

    It's as if a very-very-very mild form of compression is added with every passive part (joints, wires, pots, and switches) added to the circuit. As such, my experience when adding even minor (software based) compression to the mix has always provided me with a greater illusion of added, but less accurate Bass. Like listening to typical compressed re-master compared to the much higher DR original (w/CD or Vinyl), greater bass is near always realized with added compression ... a false illusion that many people seem to prefer.

    Now, to make matters even more interesting ... I have a direct switch on the pre-amp, so comparison is dead quick and easy. But it's near impossible to hear anything "different" manipulating the switch/test in this fashion; neither I or anyone else (blind) seems to hear any consistent difference when the test is approached in this fast "switching" blind manner. However, extended listening with the switch in either mode for a much longer period of time (a few songs at a time) provides far greater accuracy (when the listener is asked to blindly identify which switch position).

    phew ... I digress ...

    ps: Martin Barre was awesome live ... this dude rocks Tull.
     
    Last edited: Nov 20, 2017 at 6:00 PM
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  16. Fitzcaraldo215

    Fitzcaraldo215 Addicted to Fun and Learning

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    It all seems very logical, even the notion that "the quieter the turntable becomes in operation, the more resolving it becomes". Except, I am not aware that anyone is publishing operational noise measurements on turntables these days. Yes, lower noise seems a good idea. But, which ones have the lower noise? So, I guess my question would have to be how does anyone actually know this and all your inferences from that to be true? Or, is it all just a self-fulfilling prophecy inferred from the subjective end of things, as in "that turntable sure sounds good with that LP, therefore the turntable must have lower noise"?
     
  17. TBone

    TBone Addicted to Fun and Learning

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    The above is based on my own experiments with my various turntables, using a stethoscope, digital recorders, and lately, some cool apps on a Galaxy S3 which measures resonance, vibration / noise per freq. But unless you've heard firsthand based on experience, I'm not certain others could reliably tell the "better" turntable based on less noise distribution, simply listening to a stereo with all its added coloration's. But there are certainly differences, and they are very worthwhile in my books. Simply test; place a good steth on any such turntable and will probably hear all types of noises through-out its structure that you'd never hear otherwise. They will smear the sound to one degree or another ... but like I stated, eliminating or sinking noise can be very difficult ...
     
  18. TBone

    TBone Addicted to Fun and Learning

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    even a slightly out of balance platter can create internal noise, but who would go to any length to balance a platter (but silly me) ...

    The great equalizer with evaluating high-end turntables, IMO, is the use of digital rips ... one can preach all the subjective nonsense available online and some, but simply sharing a rip (and/or measuring it against the similarly mastered CD) provides a much greater degree of understanding. From what I've gathered, few analog based audiophiles, and no manufacturers I know, go that distance, many claim digital intervention will somehow change the results (it won't silly) ... hence the reliance on more & more subjectivity. I don't care much about the subjective / objective stuff people put forward, being an audiophile requires some subjective measure, just for the fun of it. And in the high-end audiophile market, subjectivity sells by the boatload ...

    I'm long past caring about subjective / objective trips, bores me silly. I work v.hard at making my system better, this is part & parcel of my existence and enjoyment within this hobby. At the same time, although I don't enjoy the frustration, I enjoy learning curve. I've often stated that if a turntable rig is that subjectively "great", rip it and share the wealth, let others decide on its prowess. Hell, never mind analog, I've recently ripped some high-end CD players (and was amazed at some of the different measurements) to illustrate digital based differences ...
     
  19. Cosmik

    Cosmik Major Contributor

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    Unless part of the turntable's special sound is due to acoustic feedback specific to the listening room, in which case its live resonance effects can't be exported.
    They say "worse", but it might be the key to 'special turntable sound'.
     
  20. Soniclife

    Soniclife Member

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    I keep meaning to try this, rip it with the replay volume up high, then again with the volume super quiet, compare the results. I think I will prefer the quiet one, but I would not put lots of money on it.
     

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