Amp voicing

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by fish78, Apr 7, 2008.

  1. fish78

    fish78 Member

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    This may be a naive and even stupid question...
    Is it possible to duplicate the sound...not considering speakers or cab...running a pure tone through the original amplifier and measuring it with an osscilicope or other device and then use that measurement to tweek the new amp until it matches? I suppose it would be necessary to do this across the spectrum and at all amp settings...but it seems thar it should be feasible...
     
  2. Blue Strat

    Blue Strat Member

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    To some degree, yes. It would require the full spectrum of guitar frequencies.

    There are lots of aspects like phase which would also have to be considered. Then, there are those aspects that we're not aware that we're not aware of which often elude us.;)
     
  3. fish78

    fish78 Member

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    You sure your name is not Rumsfeld?:worried
     
  4. Groovey Records

    Groovey Records Member

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    I Thought I recognized him !
     
  5. Blue Strat

    Blue Strat Member

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    Damn, that's insulting!

    I was hoping for something more existential :D
     
  6. Blue Strat

    Blue Strat Member

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    Hey Groovey! How'd those Mullard '34s work out?
     
  7. telemoxy

    telemoxy Member

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    :stir
    It is an interesting proposition but speaking as a musician, there are a lot of variables to consider.

    You don't hear what is going into the oscilloscope you hear what is coming out of the speaker first off so it is difficult to just say we will ignore that.

    What would you tweak? You can put the amps side by side and adjust the amps existing controls to try to match the oscilloscope image. You could play through an equalizer and play with it to get the amps close to the same sound. There can be a lot of combinations in amps with 3 and 4 band EQs, multiple gain and volume controls, presence controls and variations on that theme.

    Are you trying to match the clean, overdrive or distorted sounds or some combination.

    Are you are talking about changing components? The same components are not all the same value since the tolerances can be as great as +- 20%. that means there could be a difference of as much as 40% in the values of two resistors or capacitors. Components from different manufacturers affect the sound. You could build two identical amps and they could have different oscilloscope readings and they do. How many components are you willing to change?

    If you accept that you really can't ignore the speakers, then there is the speaker enclosure to contend with and the variables that go into its design and manufacture not to mention the output transformer.

    And the biggest consideration of course is how much time do you want to take away from playing to address all these issues.

    Did I mention there are a lot of things to consider.
     
  8. fish78

    fish78 Member

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    I am not doing any tweeking...the question went to those who build clones of other amps...they all seem to have tonal differences to a greater or lesser degree...my question was could an exact duplicate be built using the method I outlined...then play them into the same speaker cab combination and there should be no difference...just an idle question to ponder...
     
  9. Blue Strat

    Blue Strat Member

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    FYI, most (maybe all) clones have identical component values as the originals. That's why I laugh when some people say that "modern amps are voiced around new production tubes".
     
  10. Brent Hutto

    Brent Hutto Member

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    Yeah, I've always thought it funny to see these online forum discussions among amp builder who debate the minutae like whether to put a 10uF cathode capacitor in their AZ1169 circuit or go ahead and upgrade it to the 20uF like Fender used in the 5Q14 the next year...and then they put a JJ tube in there that's not really like any tube that existing in 1969 or 1951 or whatever.

    This guitar amp business is the darndest combination of irrational nostalgia and obsessive engineering refinement I've ever come across. Much moreso than the high-end audio guys. But that's probably what makes it so fascinating. It's not sufficient to make an amp that sounds great, it also has to have some certain amount of throwback credibility or nobody will care what it actually sounds like. Gotta be a tough way to earn to living.
     
  11. donnyjaguar

    donnyjaguar Member

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    I do believe this is what the DSP guys do to model an amplifier after a vintage one. I have a solid state DSP one that's pretty convincing this way, but generally more so when the headphones are plugged in.
     
  12. GearHeadFred

    GearHeadFred Member

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    Very interesting and non-stupid question!

    Yes, the amp modelers such as line6 etc. are doing exactly this. Think of the amp 'operating' on the input signal to produce the output signal.. The perfect modeling amp would produce the exact same output for all given inputs as it's real amp counterpart.

    But, as they say, the devil is in the details! Spectral response is only one element of what a guitar amp does to the input signal. There are several others (compression, signal-to-noise, etc.). And it turns out there are so many parameters and variables that doing this is difficult even with state-of-the-art technology.

    Pretty amazing (and cool) considering these things were designed in the 1950's, and we are still trying to (re)capture that magic.
     
  13. vibroverbus

    vibroverbus Member

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    +++1 (+3?)

    in some ways the audiophools tend to more rational - less blind worship of specific exact ancient designs and designers (no, Leo Fender did NOT invent the guitar amp or even any particular electronic engineering concept, he just 'tweaked' his way to greatness). but in other ways more out there - more blind worship of imaginary magic mojo capacitors and 'tone lacquer' or whatever that snake oil is called (but just in case it works I just painted my entire collection of amps and slathered some on my package for good measure). http://www.altmann.haan.de/tubeolator/default.htm


    +1 again
     

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