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Hey Sebatron- Questions for You, Buddy

Discussion in 'Pro Audio Equipment' started by Doc@BeefyTreats.com, Sep 15, 2003.

  1. Sebatron,
    If you wouldn't mind to take a minute for explanations, a couple of questions about the preamps:
    1. What frequencies get boosted or cut when the "Air", "Bright", "Deep", and "Low Cut" features are activated? Confirm: the first three of those are boost while "Low Cut" is a cut? How much is the boost/cut? Please describe the character of the boost/cut (shelf, peak, Q, etc).
    2. The pad is the only way to control input gain-true? What if the input signal is weak and needs some gain?
    3. What kind of tubes are in there? What kind of transformers?
    Inquiring minds want to know. Thanks, David
  2. Sebatron

    Sebatron Well-Known Member

    Dec 22, 2002
    1/The E.Q functions on the vmp series preamps are intended for subtle enhancement or correction before committing sounds to tape/DAW.They are wide-Q and either open up the top or bottom register.
    This is , yes , a boost type E.Q.Starts very low , from 15 hz.
    +1db @ 20 hz
    +8db@ 40hz ….. peak
    +5db @ 55 hz
    +1 db @ 320 hz
    I actually think the peak is the bottom ‘E’ in frequency .

    AIR: The ‘air’ and ‘ bright ‘ settings have a different curve/Q , depending on the pad level switch setting.
    With 0 db pad selected:
    +1 db @ 6.2 khz
    + 4 db @ 14.5 khz……… peak
    +1 db @ 30 khz
    flat again at 38 khz

    With –15 db pad selected:
    +1 db @ 4.2 khz
    +5 db @ 9.4 khz
    +9 db @ 26.4 khz ………peak
    +5 db @ 62 khz
    flat again at 88 khz

    With –30 db pad selected:
    +1 db @ 4.2 khz
    + 5 db @ 12.6 khz
    + 6 db @ 20.6 khz………peak
    + 5 db @ 33 khz
    flat again at 58 khz.

    With 0 db pad selected:
    +1 db @ 3.3 khz
    + 4 db @ 5.8 khz
    + 5 db @ 11.8 khz ………peak
    +1 db @ 30 khz
    flat again at 38 khz

    With –15 db pad selected:
    +1 db @ 2.4khz
    + 5 db @ 5.4 khz
    +9 db @ 20 khz ………peak
    +5 db @ 60 khz
    flat again at 88 khz

    With –30 db pad selected:
    +1 db @ 4.2 khz
    + 5 db @ 6.2 khz
    + 8 db @ 16.8 khz………peak
    +5 db @ 38 khz
    flat again at 58 khz.

    These are just basic plots but you can see how sweet those frequencies are… particularly those peaks , they are way above that horrible top-mid area.

    2/ The new vmp design features an upgraded gain structure/circuit giving up to 60 – 70 db of gain.
    If more gain is required , you can easily link two channels together for a massive magnification.

    3/ We use J.J tubes ( 12at7 ) , and locally sourced hand wound audio transformers.
    Occasionally I have used OEP audio transformers with identical results. :w:
  3. Sebatron,
    Much good info, thanks. Chris is sending me a unit to check out. Double smiles. David
  4. gefell

    gefell Guest

    the sebatron mic pre is one of the most uniquest mic pre's i have worked with.

    believe the hype!!!!!!
  5. sc1767

    sc1767 Guest

    Yes, Sebatron, thanks for posting that info.
    Very interesting how the pad switches affect the eq response. Hmmm...so many options; I'll be doing a ton of comparative listening. May I suggest adding that to your owner manuals? Ha, I guess I just did.
  6. Sebatron

    Sebatron Well-Known Member

    Dec 22, 2002
    …good idea SC…
    I’ve been meaning to plot those graphs for a while ,
    I didn’t realize they peaked so high ‘till I did that recent sweep.
    Most of what I do is dictated by ear.

    Yes , the variable pad level makes the circuit quite flexible from being transparent to coloured and the EQ circuit interacts with the negative feedback loop to provide many options….
    Let’s see…. 3 * 3 * 3 => 27 colours in all.

  7. Hey Sebatron,
    I got a hold of Chris's vmp today. I tracked some electric guitar, and compared it to the Universal Audio 2-610. I am impressed. The vmp held up well against the 2-610. I found the vmp to be a little more defined in the high end. I do prefer the eq of the 2-610, in both sound and functionality, but I understand that the eq function on the vmp is designed to perform corrections to pre-DAW signals. Not a knock on the vmp, however, all the eq buttons sound right. All in all, serious kudos- the UA is my favorite preamp and I was NOT disappointed by the vmp. Tomorrow I hope to track some bass. David
  8. Kurt Foster

    Kurt Foster Distinguished Member

    Jul 2, 2002
    77 Sunset Lane.
    One thing I have found that the vmp really shines on is acoustic guitar. I used a U87 aimed at the point where the neck joins the body of my Martin D28 and the sound is absolutly huge! I also really like the front panel 1/4" inputs, using them for drum machines and synths. The vmp really warms up these digital 16 bit babies! Give both these techniques a shot while you have Chris' unit there.
  9. Thanks Kurt,
    I did some bass DI through the Seb yesterday and dug it. Tomorrow I am going to do some vox and acoustic guitar, wish I had an 87 laying around. I will give my humble opinions on that application later. David
  10. mikE@THECAVE

    mikE@THECAVE Guest

    hey Mujtaba what other pres have you been using

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