The Hi-Fi News Test Record: Inaccurate Resonance Tones

Discussion in 'Audio Hardware' started by OcdMan, Sep 5, 2008.

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  1. OcdMan

    OcdMan Forum Resident Thread Starter

    Location:
    Maryland
    Out of curiosity, I recorded the lateral and vertical resonance tones on the Hi-Fi News test record into Adobe Audition and then checked each one using the frequency analysis feature. I believe the results are accurate to within a couple of tenths.

    Lateral

    Claimed Hz = Actual Hz


    25 = 24.5 then down and up a couple of Hz

    23 = 21.75 then 19.25

    21 = 19.25 then 17.5

    19 = 17.5 then 15.8

    17 = 15.8 then 14.4

    15 = 14.4 then 11.7

    13 = 10.9

    11 = 10.4 then 8.7

    9 = 8.8 then 7.2

    7 = 6.2

    5 = ?


    Vertical


    20 = 20

    18 = 17.8

    16 = 14.4 then 11.75

    14 = 10.9

    12 = 10.4 then 8.7

    10 = 8.85 then 7.2

    8 = 6.2 then ?

    6 = ?
     

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  2. Koptapad

    Koptapad Forum Resident

    You mean kilohertz I suppose.

    I bought the Cardas Test Record and was a little disappointed. I never measured the frequency as accurately as you but I found the reference tones wavered up and down a small amount too when I examined them on my DAW. I think maybe because the test record spindle hole was off a tiny amount. I could see the cart sway just a bit.
     
  3. Joe Nino-Hernes

    Joe Nino-Hernes Active Member

    Location:
    Chicago, IL
    What turntable are you using? The slight variation in pitch is most likely caused by your table.
     
  4. BigE

    BigE Forum Resident

    Four posts in and I can already see where this is going . . .:eek:

    I thought once a direct drive table locked on the pitch variation, even if off-pitch, would be constant. Maybe it's his mains causing the variation not the motor. I assume he's using the 1200 listed in his profile.

    Not that I want to start another 1200 flame-war.

    Eric
     
  5. Joe Nino-Hernes

    Joe Nino-Hernes Active Member

    Location:
    Chicago, IL
    Technics tables are fine entry level decks, but you are not going to have super accurate speed until you really spend some money.

    Those test disks are very accurate. If there is any pitch variation, you should suspect your turntable, not the test disk (unless the disk was pressed off center).

    I notice things like this with my tape decks. If I thread up an MRL tape one one of my Tascam decks, I can hear slight variations in pitch. If I throw it on my Ampex ATR, the tone is rock solid. The Ampex is in a totally different class, and its unfair to even compare it to the Ampex. With that said, the Tascam is a great deck for what it is, but its simply not in the same league as the Ampex.

    If a $600 table was perfect, there would be no market for the high end stuff. High end tables are expensive for a reason. It costs money to design and execute a good sounding, speed accurate table. Don't take this the wrong way, I'm not bashing the 1200, but I'm just saying there are better things out there.
     
  6. MikeyH

    MikeyH Stamper King

    Location:
    Berkeley, CA
    That's usually the case. You should center the groove visually (with a microscope) before critical measurements. Serious test discs have a non-spiral cut groove at the edge so you can do this easily.

    IIRC something like 1/10mm is .15% wow: You don't see that figure on turntables these days, and it explains why those with perfect pitch have some trouble with records (unless they use the old Nakamichi self-centering table)
     
  7. Toka

    Toka Active Member

    I was going to ask just that question (spindle hole), as well as to verify that everything was flat/level and the in proper alignment. The 'table itself does have stellar speed accuracy, among the very best around (at any price), in fact.
     
  8. Guys - before this thread goes along the lines of checking for wow, off centre disc and such:

    This isn't the first time this has been reported; members of other forums have reported the same. Matt isn't describing a "variation" in pitch as such (as alluded to in post #4). He is reporting a descrepency between the frequency being described by the commentary on the disc, and the actual frequency occuring at the time (slight difference, but worth mentioning). The "up and down a couple of hz" he mentioned in his post is literally the frequency generator being adjusted, then re-adjusted - easily heard playing a recording of this test back at 4x normal speed.

    Anyway. As I couldn't find any concrete links to other reports of this, I have just tested it myself :). I used an EQ plugin within Wavelab 3, setting the slope/Q factor to it's narrowest, boosting heavily and finding the reported hotspots. I made sure the disc was centered, and that the strobe was showing true speed.

    Here's what I got (horizontal resonance test only); figures are taken from each moment the frequencies are announced on the disc:

    25 Hz = 24.4 Hz
    23 Hz = 21.6 Hz
    21 Hz = 19.6 Hz
    19 Hz = 17.2 Hz
    17 Hz = 15.7 Hz
    15 Hz = 14.5 Hz
    13 Hz = 11.1 Hz
    11 Hz = 10.8 Hz
    9 Hz = 8.7 Hz
    7 Hz = 5.7 Hz

    5 Hz was too low for me to measure. My figures aren't that far off from Matt's.
     
  9. Publius

    Publius Active Member

    Location:
    Austin, TX
    Yeah, John Elison found this out the hard way a few years ago and posted about it on Vinyl Asylum:

    http://db.audioasylum.com/cgi/m.mpl?forum=vinyl&n=594322

    His turntable is mostly beyond ill repute as far as speed stability goes. I've noticed it on both my MMF5 and my 1200. It's there. The vertical resonance test also spontaneously changes in level quite drastically in the middle of itself.

    There are also questions about the quality of the other tracks, too.... the sweep has some weird issues iirc, like that the noise goes through the roof well before it hits 20khz, and its sweep speed is nowhere near constant.

    I've heard some superlative things about the Ultimate Analogue Test LP, and Vinyl Engine has some great protractors, so that might be a more recommended solution. Hopefully some funds will open up this year so I can give that test record a whirl.
     
  10. OcdMan

    OcdMan Forum Resident Thread Starter

    Location:
    Maryland
    Exactly.

    This is NOT wow and flutter that I'm talking about. When the voice announcement says "13 Hertz" the tone is actually right around 11 Hz. My turntable would have to be running 15% slow to create an error like that. :laugh:

    I centered the record and also checked the strobe. The slight discrepancies between Phil's and my measurements are probably due to the software we used and/or where we took the measurements because, as he said, playing back the track as 4x speed you can hear the tone generator being fiddled with.
     
  11. OcdMan

    OcdMan Forum Resident Thread Starter

    Location:
    Maryland
    Thanks. John Elison uses a SOTA Millennia. Here are his results from the link above:
     

    Attached Files:

  12. Publius

    Publius Active Member

    Location:
    Austin, TX
    Methinks that Len just fiddled with some signal generators by hand to make most of the tracks. That certainly explains what Phil is seeing, and what I saw with the sweep. But it also calls into question the pitch accuracy of the 300hz tones. Or, for that matter, exactly what gear did he use to cut the white noise tones?
     
  13. John Elison got his measurements from the old HFN disc, whereas I got mine from the newer one. Neither appear to be correct.

    The pink noise tracks are variable on my disc; the two channels aren't in agreement on the mono track, and are different from the left and right channel only tests. This is with 3 different cartridges, btw.
     
  14. OcdMan

    OcdMan Forum Resident Thread Starter

    Location:
    Maryland
    Mine look almost identical to his except I used the newer one. Maybe some newer ones were pressed from the old stampers? Either way, both new and old are wrong. Like you, I've noticed inconsistencies with the other tests as well. What a waste of $40!
     
  15. No kidding. Considering we are talking three different turntables, and two different editions of the disc, that speaks volumes.

    At least I now know what the frequencies really are; which is crucial when the arm resonates close to the acceptable boundaries. Like mine does ...
     
  16. Publius

    Publius Active Member

    Location:
    Austin, TX
    Yeah, now that I've tried Seb's protractors at Vinyl Engine, I see no reason for anybody to buy HFNRR. The torture tracks are not that important for antiskate adjustment and a lot of the other tracks are kind of questionable.

    So which one of us is going to spring for the Ultimate LP first?
     
  17. Koptapad

    Koptapad Forum Resident

    What happens when the arm resonates? Can you describe it please?
     
  18. Joe Nino-Hernes

    Joe Nino-Hernes Active Member

    Location:
    Chicago, IL
    I stand corrected! Looks like the disk actually is at fault. I find that rather bothersome. It defeats the purpose of the disk, as a test disk is supposed to be a perfect reference to measure your table against.

    I still use the old CBS labs test disk from the 60's. I know for sure that it is correct.
     
  19. Publius

    Publius Active Member

    Location:
    Austin, TX
    At those frequencies, resonance means that the cartridge visibly moves up and down. In theory, at the very least, that can mean a significant dynamic change in VTA across a lot of LPs. It also can cause wow/flutter on its own in more extreme cases. It also causes large dynamic swings in VTF, so mistracking may become more common than it should be with warped records, or when a lot of subsonic environmental noise is coupling through the table mount (like a train/subway/etc).

    Resonance happens with every tonearm - it's a mechanical parameter of the system.
     
  20. The youtube clip I posted shows the horizontal test in action; the cartridge literally wobbles from side to side at the resonant frequency. The vertical test does the same thing in the vertical plane.

    Why do we worry about this? The ideal resonance is somewhere between 8 and 15 Hz. If it's too high, this resonance will be an audible artifact in the actual music. Too low, and the turntable will have difficulty dealing with warps, and external vibrations.

    The resonant frequency is a direct result of the mass of the arm, and the compliance of the cartridge/stylus (or "stiffness", to put it crudely). If you know the arm mass and cartridge compliance value, you can calculate the resonant frequency:

    http://www.theanalogdept.com/cartridge___arm_matching.htm
     
  21. Orlan K

    Orlan K New Member

    Location:
    Overland Park, KS

    The newer direct drive Asian tables are PLL controlled and their pitch (speed) accuracy is a direct function of the internal clock and PLL. While this reference time base is not necessarily incredibly precise, it should be _constant_ over a period of time as long as the temperature of the crystal reference does not vary very much. Their speed may be much MORE accurate than much more expensive belt drive tables.

    Belt drive tables have as variables the diameter of the motor and drive pulley and belt thickness. They DO wear.

    That's also true of the servo motor driven capstanless ATR Ampices. They don't have a OCXO or an external 10 MHz standard derived clock as far as I know. The system clock is a crystal on a board.

    Classic Ampex decks-300, 350, AG351, AG440 and the MM series-had AC synchronous motors which are as accurate as the line frequency. Which may be less than that board mounted crystal. If extreme accuracy is needed you need an electronic AC supply with a reliable timebase. The ATRs may have a little better specs, but oh, the TTL troubleshooting needed if they go awry!

    In a world where 300, 350 and even 440 transports are _cheap_ why use any other transport? Dunno!
     
  22. Joe Nino-Hernes

    Joe Nino-Hernes Active Member

    Location:
    Chicago, IL
    I would love to get an AG-440. They are really nice machines. I love my ATR but it is not always reliable. I would like to have it rebuilt by ATR Services. Mike does amazing work on those decks!
     
  23. I have one of them. Bought it for $200. Needs new cars though. The pots are dead.
     
  24. Joe Nino-Hernes

    Joe Nino-Hernes Active Member

    Location:
    Chicago, IL
    Do you plan to get it up and running? They are really great decks! I guess the bigger question is, do you run much tape these days :sigh:
     
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