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Ultra High switch on SVT CL

Discussion in 'Amps and Cabs [BG]' started by Dallyd31, Aug 16, 2007.

  1. Dallyd31

    Dallyd31 Supporting Member

    Jun 22, 2005
    Peterborough, Ontario
    What frequencies does this button add ??? Also, does it cut other frequencies in order to accentuate the highs ???

    Just wondering exactly what frequencies this switch adds/cuts
  2. RickenBoogie


    Jul 22, 2007
    Dallas, TX
    Not sure about the frequencies, but NO CUT, just boost.
  3. Masher88

    Masher88 Believe in absurdities and you commit atrocities

    May 7, 2005
    Cleveland, OH
    I think it may cut the mids or something. It definitely does more than just boost highs
  4. nysbob


    Sep 14, 2003
    Cincinnati OH
    I leave it off. :meh:
  5. sedan_dad


    Feb 5, 2006
    Oh yea. I guess there is one.
    I never touch it.
  6. Jazz Ad

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    It's great to use when your strings are dead and you want some bite in your tone.
  7. Dallyd31

    Dallyd31 Supporting Member

    Jun 22, 2005
    Peterborough, Ontario
    I was under the assumption that it not only boosted some frequencies, but also cut some others to accentuate the highs. But I can find any confirmation of that anywhere.
  8. I'm not sure if it's 100% the same, but in my V4BH manual it says...

    "ULTRA HI: This swith boosts high frequencies."

    "ULTRA LO: This switch, when depressed, provides emphasis to the low frequencies by boosting the low frequencies and selectively cutting the mid frequencies."

    Should be the same in the CL, I believe.
  9. el_Kabong


    Jul 11, 2005
    How hard did you look? ;)

  10. +9dB @ 8 kHz.

    You're welcome.
  11. el_Kabong


    Jul 11, 2005
    Awww come on Keith, at least make him rtfm.
  12. Dallyd31

    Dallyd31 Supporting Member

    Jun 22, 2005
    Peterborough, Ontario
    Thanks for the help Kieth.

    BTW,I DO have the manual, but last time I checked, it didn't have the amount of boost or the frequency it was boosted at, which is what I was after.

    When I engage it, it still sounds like it cuts a frequency somewhere, but that could just be my ears.

    Thanks gain Keith
  13. The idea that you hear a frequency cut is probably due to your tweeter being very close to your ear or the tweeter is much more efficient than the woofer in your setup. It's a weird one: a bass heavy mix can be easily tamed with adding more sound in the tweeter range - I think it has to do with high frequencies traveling much faster to your ears and the fact that high end is easier to hear than low end. So boosting the highs too much pretty much gives the illusion that the bass content of your signal has diminshed - even though the bass is pounding very loudly, the extra tweeter noise will bring the bass Sound Pressure Level down a few notches.

    I am not an Engineer - but it makes sense to me!
  14. One Drop

    One Drop

    Oct 10, 2004
    Swiss Alps
    Engaging the high boost on my '72 SVT certainly sounds like it does more than just a boost at that frequency. it could be a psychoacoustic effect but if it is it's big enough to affect the audience as well, and I'm not fond of it at all.

    The low boost is a tone suck button as far as I'm concerned- too much mids get lost, not very nice with a fridge or my NV610.
  15. Masher88

    Masher88 Believe in absurdities and you commit atrocities

    May 7, 2005
    Cleveland, OH
    I didn't look! hahaha. Just going by what it SOUNDS like when I push it in...which I almost never do.

    Judging by other posts, they hear the same effect.:smug:
  16. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    I'd have to look at the circuit to give the best and most definite answer, but.....

    You will notice that the specs DO show a cut for the "ultralow". So it isn't as if the evil ones at Ampeg are hiding anything, they 'fess up about the UltraLow.

    I can see why it might sound like a cut, though. The actual response is as if you DID do "V" type curve on a graphic EQ, and then also added a "tilt up" in the response that was across all frequencies. Sort of as if you drew a wide "V" on a piece of paper, and then turned the paper until the left side of the V was horizontal.

    Your ears are funny things. Some people are very sensitive to small "tilts" in the overall response. So if someone thinks it sounds like a cut, I'm OK with that.
  17. okabass


    Mar 19, 2005
    Ultra Hi is different in the old or original SVT pre and Classic pre. Both are simple, but effective circuits.

    Old ones UH is a switchable treble bleeder cap (500pF) at the volume pot. According to manual it gives +20dB at 8kHz (~treble "boost") when volume pot is set low (ccw) . When pot is full (cw) it has no effect.

    The Classic pre UH has a switchable 33nF bypass cap at V1 tube (second tube stage) cathode. It makes a +6dB shelving eq . Its -3dB point is around 3,6kHz (-3dB from the full 6dB boost ). It is that kind of curve.

    The 33nF bypasses the 15k+1k5 cathode resistors. The tube is 12AX7 and anode resistor is 100k. Can anyone confirm my calculations?
  18. el_Kabong


    Jul 11, 2005
    Yeah, and you wuz wrong. hahaha!!


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