high input vs low input on a guitar amp

Discussion in 'Amps and Cabs' started by music321, Nov 9, 2012.

  1. music321

    music321 Member

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    i've always assumed that low input jacks referred to single coils, while high input meant humbuckers. now i'm thinking that low input is a dry signal, while high is through a boost? is this wrong?

    if i have an amp w/ only one input, can it be optimized for high or low input?

    it seems that the best way is to start with one configuration, then use a pedal to bring it up to spec of the other. any ideas?
     
  2. Walkerjerry

    Walkerjerry Supporting Member

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    The opposite, actually. A "low input" usually is a padded input, while the "high input" is actually the stock circuitry. As for their use, it depends what you want from your amp; more gain, use the high side, more headroom, the low side. A more technical explanation available upon demand.
     
  3. bgood

    bgood Member

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    How does the pad typically work? Does some of the guitar signal connect to ground at the jack to pad it down?
     
  4. sleewell

    sleewell Member

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    i dont think either of the OP's theories are correct. i think i just depends on the sound you are looking for. my fender has 2 inputs and #1 is much brighter than #2. both have their places and work with any pickups or pedals.
     
  5. Onioner

    Onioner Member

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    Yup.
     
  6. Sirloin

    Sirloin Supporting Member

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    Some input jacks are just wired with a single resistor for the low input jack and two resistors in parallel for the high input jack. Single resistor=Higher resistance=lower signal hitting the front end of the amp. Two resistors in parallel=lower resistance=hotter signal hitting the fron of the amp. I think this is the way 4 hole Marshalls were wired.
     
  7. big mike

    big mike Marshall Voiced Moderator Staff Member

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    Depends on the amp.

    At least one I've had, the '2' input was a differnt voicing.
     
  8. Onioner

    Onioner Member

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    Fwiw, regardless of inputs available, I've learned that using a volume pedal (like the Barber Launch Pad) to find the ideal input strength leads to huge rewards. Only pedal i use regularly, and at this point i wouldn't want to do without it.
     
  9. jazjamr

    jazjamr Member

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    I have been using the low inputs on my vintage Fenders with single coils. These amps sound much better with the power tubes turned to the 6 to 8 range. I can drive the power tubes this way at a lower volume. If I need more headroom I plug into the #1 jack.
     
  10. music321

    music321 Member

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    jaz,

    you get breakup earlier with the low input?

    The volume pedal idea sounds interesting. If I understand all this correctly, then am I right to assume that using a volume pedal with a single input will essentially yield the same result, just with more options, than having a "low" jack in addition to the "normal" (high) jack?
     
  11. Onioner

    Onioner Member

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    Yup. You can tailor the input strength to the guitar, amp, and intended use.
     
  12. aflynt

    aflynt Supporting Member

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    For a sound somewhere between the two on Fenders you can plug into input 2 and put a dummy plug into input 1.

    **caveat** - the plug needs to NOT be shorted. IE: no connection between tip and sleeve.

    -Aaron
     
    Last edited: Nov 9, 2012
  13. GuitarNorton

    GuitarNorton Member

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    Yes I use a Launch Pad the same way, always on, gain staging is how Dave Barber puts it. Really makes a difference
     
  14. EADGBE

    EADGBE Member

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    My Marshall's 2203X 100 watt master volume owner's manual says that originally the high input was designed for single coils while the low input was designed for humbuckers. But in no time flat everybody was playing their humbucker guitars through the high input. [​IMG]
     
  15. Cirrus

    Cirrus Member

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    When there's a bright cap across the preamp volume knob, having a high and low input can be really useful - for example, on my amp having the bright cap switched in makes it too bright, having it switched out makes it too dark. But by using the low input I can turn the preamp volume higher to get the same amount of breakup, and have a less trebly tone with the bright cap switched in (the effect of the cap reduces as the knob is turned up)
     
  16. rastaman

    rastaman Supporting Member

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    I once plugged into the low input of my 2204 (w/ a LP w/ humbuckers) just to get a better handle on my volume at a small rehearsal space. I think it also bypasses on of the preamp stages for less gain. Anyhow, I got a whole lot better clean tone and with the right pedal, my tone was surprisingly kick ass!! FWIW, we were doing some original material with a Keith Urban flavor. But, with the right pedal, say an OCD, Wampler, Riot, you could get into heavier territory.
     
  17. jazjamr

    jazjamr Member

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    Using the low input jack keeps the preamp stage clean, while driving the power tubes harder. This is the principle SRV used with a 5751 preamp tube in the 1st position. My old Fenders dont really sound good until you get them up to at least 5 on the volume knob. . I play a 1966 AA763 Showman Amp with a single Weber Michigan speaker. The Michigan is a lower DB speaker than my Weber California . Using this method gives me an approximate 20% reductiom in volume. For a larger venue I plug into the#1 input jack.
     
  18. tapehead

    tapehead Supporting Member

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    +1 for the Launch Pad. Function versatility level: DMM.

    With regard to the high input vs low input...I'm fairly certain it has to do with the resistance. Typically 1Mohm for high and 47k for the low.
     
  19. rob2001

    rob2001 Member

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    I read that in my 1984 JCM 800 manual as well, but I never cared!
     
  20. '58Bassman

    '58Bassman Member

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    They called one 'Normal' and the other 'Bright' and it has little/nothing to do with signal level. If it has Hi (or High) and Lo (or Low), it referred to sensitivity. Low sensitivity means the signal is reduced at that jack and they used a dividing network, which consists of the two resistors shown on the schematic- one in series and one parallel to that, going to ground.
     

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