RIAA Curve

Discussion in 'Mastering' started by FifthCircle, Dec 12, 2005.

  1. FifthCircle

    FifthCircle Well-Known Member

    Currently doing a few vinyl transfers for an archival project through a flat preamp... On some of the recordings, I'll need to apply the RIAA curve, but I've had a bit of a difficult time finding exact numbers for it. I know on playback it involves a pretty substantial bass boost and a high cut, but I don't know much else...

    Thanks in advance...

    --Ben
     
  2. audiowkstation

    audiowkstation Active Member

    With vinyl, you will need the eq curve on all of them.

    I will see if I can put together something for you. I am under the assumption these are LP33.33 and or 7" 45 from 1958 forward?

    If they are LP51-58, another set of curves may be needed and the UK standard for the 50's period..yet another. For 78 RPM, 3 curves were used depending on date and mastering facility.

    I know of NO.. post 1958 vinyl that did not use the eq.


    Personally, I have not met a great argument as to why a flat eq is preferable. It will result in so much custom tayoring needed that "how do you know if you are really close?"


    newway1.jpg
     
  3. FifthCircle

    FifthCircle Well-Known Member

    Thanks Bill

    :cool:

    --Ben
     
  4. jase

    jase Guest

    If they are 33+45 this will be fine. At least you know its correct.
    http://www.studiospares.com/pd_404190_ALICE RIAA PAMP.htm
     
  5. dcollins

    dcollins Guest

    There are several reasons why you should not do transfers like this!

    The biggest is that you aren't loading the cartridge with the 47k and around 100pf needed for proper response.

    You need to get a RIAA preamp and forget about tring to eq after the fact!

    "RIAA curve" in Google will get you started, if you wan't to know the origins of the curve.

    DC
     
  6. audiowkstation

    audiowkstation Active Member

    Here is the resource for Phono cartirdge loading, depending on inductance, desired frequency response and a few other factors.

    This of course is based on pre RIAA eq.

    http://www.hagtech.com/loading.html
     
  7. dcollins

    dcollins Guest

    Do you catch the basic error in this site?

    Other than that, the only factors are RLC, and if you are feeding your turntable into a mic pre, with an input impedance of like 2k, you are off by 50 times!

    Let's forget digital eq for this one as well.....

    DC
     
  8. FifthCircle

    FifthCircle Well-Known Member

    I've changed stream and redone some of the work that I just wasn't happy with- (cartridge loading is I'm sure a portion of it).

    I've purchased a good preamp with the ability to change the loading of the cartridge and the sound has improved markedly...

    -Ben
     
  9. audiowkstation

    audiowkstation Active Member

    Good going Ben...hence my previous statement, quoted here...


     
  10. FifthCircle

    FifthCircle Well-Known Member

    Yeah, I was trying to do what I knew I shouldn't do- take a shortcut and save a few bucks (my old vinyl setup was in need of help). I was actually going through a direct rather than just a mic pre so that the impedance would be a bit closer. Still not an ideal situation, though. The new turntable and preamp should be here within the next couple days.

    --Ben
     
  11. audiowkstation

    audiowkstation Active Member

    Look carefully when setting up your table. VTA can make quite a difference to overall traceability.

    I tend to go toward the "higher side" with the tracking force issues as well.

    Clean the albums very well. Many techniques are out there..you won't hurt the vinyl by doing some pretty major scrubbing if required. It does withstand a diamond..propped up by the groove walls, at tons per in sq!
     
  12. dpd

    dpd Active Member

    take your cartridge drop it from a slight height onto a non-rotating LP and capture the time response of the output. FFT it and get the spectral response. EQ as necessary

    Sounds bizarre, but this gives you the true transient response of the entire cartridge/arm system
     
  13. audiowkstation

    audiowkstation Active Member

    dpd...I am afraid that technique would be futile with my arm/cart. Breaking a 1200 dollar cantilever is not in the plan for me. It would do nothing but give me a flat wallet and a boost of about 90dB at 7Hz..amongst other ills...

    Never tried it. I might try it with my cheaper system...but I am interested in how you found this info out...hell..he may have something here.. (?)
     
  14. dpd

    dpd Active Member

    Bill:

    Yeah, the thought of me 'dropping' my Monster Alpha II onto vinyl 20-some years ago brought shivers to my spine. You don't need to drop it much - obviously, one wouldn't want to damage the cantilever. A very slight amount should send a mechanical impulse into the system which will then cause it to exhibit its natural resonance; just like we do in electronics - excite an electrical system with an impulse reveals a system's complete response.

    With the gear we have now, capturing the unequalized response and then spectral processing via FFTs is pretty easy. That required close to $50K of gear back in the 80's.

    Never do anything that makes you feel uncomfortable, for certain. As you stated, you can always try it with a less expensive system to see how well you can acquire and process the data.

    I like the PSpice model, too - assuming you can get all the information on the cartridge. The problem with that solution is that it totally ignores the mechanical resonance between the compliance of the cartridge, the equivalent mass of the cartridge and the arm and the damping in the arm. One can model all of that, too, if the tools are available and you can get accurate measurements to feed the mechanical model.

    Sometimes, it's easier to obtain the information empirically. Caveat emptor.
     
  15. dcollins

    dcollins Guest

    You only have to drop it a few mm, it won't break anything! Even if you had the Spice model of the cartridge, I agree that giving it a "whack" is the best way to find the impulse response.

    Was it Dick Heyser that wrote about this in the '70's? Somebody like that.

    Otoh, if you had a good cartridge like a V15, and even a decent arm, the system resonance is well damped and below my cutoff freq.

    DC
     

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