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definition of specs!!/?

Discussion in 'Recording' started by odog, Jun 7, 2004.

  1. odog

    odog Guest

    i am fairly new at recording and am actually just learning a bunch from this forum thanks for all your guys advice..

    i was just looking at a preamp on ebay and saw all of its specs.. i was a bit cofused... i know some of the laydown to what they all are but am not deffinatly sure.

    so if u guys that know what all these mean can just give a quick explanation on what they are ....im sure it will help a bunch of people out not just me ..

    thanks...here they are..

    frequency response: 20Hz-100kHz, +/-0.5dB @ max gain


    signal-to-noise ratio: 116.3 dB

    THD: 0.05% @ minimum gain

    max input: +13.7 dBu

    max output: +27.5 dBu

    input impedance: 3K ohms balanced

    EIN: -128 dBm @ 600-ohms

    gain range: 13.5dB to 46.5dB (low gain range)

    34.5dB to 67.5 dB (high gain range)

    low-cut filter: -3dB @ 72Hz
     
  2. Kurt Foster

    Kurt Foster Distinguished Member

    frequency response:
    This is the overall response of the mic pre. from very low to very high ..

    signal-to-noise ratio: This is the difference between the noise level and the max output of the pre.

    THD: true harmonic distortion

    max input: just what it says

    max output: same thing

    input impedance: the optimal input impedance (resistance) of the input.

    EIN: electrical input noise.

    gain range: How much gain the device provides.

    low-cut filter: whre the lo cut filter is placed and at what rate it attenuates the low freqs.
     
  3. nuclearmoon

    nuclearmoon Guest

    I always thought it was TOTAL harmonic distortion....is this not right?
     
  4. Ethan Winer

    Ethan Winer Active Member

    Dog,

    > frequency response: 20Hz-100kHz, +/-0.5dB @ max gain <

    The range of frequencies passed, in this case from the lower limit of hearing (20 Hz) to far beyond what anyone can hear, and with less than half a dB of variation.

    > signal-to-noise ratio: 116.3 dB <

    That's quiet enough for anything you're likely to record.

    > THD: 0.05% @ minimum gain <

    Total Harmonic Distortion. This too is well below the limits of audibility. More important than THD is IM, or Intermodulation Distortion.

    > max input: +13.7 dBu <

    The loudest signal the unit can accept without distorting.

    > input impedance: 3K ohms balanced <

    Input impedance specifies how much of a load the preamp presents to whatever you feed into it. 3K is very low for a line input - 10K to 100k is more typical - but it's fine for a mike input.

    > EIN: -128 dBm @ 600-ohms <

    Equivalent Input Noise, or the unit's residual noise/hiss. The -128 claimed is very close to the theoretical minimum, so that's acceptable. The word "equivalent" means how loud an equivalent noise source fed into the preamp would have to be to get the same amount of hiss at the output.

    --Ethan
     
  5. Kurt Foster

    Kurt Foster Distinguished Member

    Thanks for the corrections guys .. I thought I might get burned on this one but I stuck it out anyway ... Kurt
     
  6. odog

    odog Guest

    thanks alot guys this helps out a lot
     
  7. realdynamix

    realdynamix Well-Known Member

    :D Got a question???? (hand waving in the air)..on that nice signal to noise figure, what is IT in reference to ???? Is it the high gain noise figure, low gain, or off?

    BTW Kurt, THD, True is totally cool with me! :wink:

    --Rick
     
  8. nuclearmoon

    nuclearmoon Guest

    Hey, Kurt I looked at this post TWICE and was too scared to tackle it, so you are still my hero!! :D
     
  9. Ethan Winer

    Ethan Winer Active Member

    Rick,

    > on that nice signal to noise figure, what is IT in reference to ???? Is it the high gain noise figure, low gain, or off? <

    Signal to noise is related to total dynamic range, but usually includes some (unspecified) amount of headroom. As far as I'm concerned, especially in this digital age, all that really matters is total dynamic range. That is, the difference between the loudest signal you can possibly achieve compared to the residual noise from the unit. I'll determine for myself the optimum operating level, and how far below hard clipping the "average" level should be.

    To complicate matters further, residual noise usually varies with gain. For microphone preamps the noise is generally lowest when the gain is highest - after you take into account the gain. So for a preamp that has a gain range of 20 to 60 dB, the dynamic range actually increases at higher gain. Of course, with lower gain you don't care so much because the input level is higher, so this is not usually a problem.

    --Ethan
     

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