Clean boost sound difference--Opamps vs. FET??

Discussion in 'Effects, Pedals, Strings & Things' started by Phil M, Jul 26, 2006.


  1. Phil M

    Phil M Supporting Member

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    This is kind of a vague question so I apologize for that. I'm hoping one of the builders or technically informed folks will understand. What kind of sound differences might one expect from the various types of clean boost pedals? I've had the TC Jauernig Luxury Drive and the Time Machine Boost (modern side), which I believe are both opamp based. How does a FET based clean booster differ in sound?

    Thanks,

    Phil
     
  2. g3rmanium

    g3rmanium Member

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    From what I know (Opamp Design is a good resource), the first opamps had really low slew rates which meant you couldn't have much gain and still amplify the full audio range (20-20000 Hz). This is exploited in designs like the MXR Dist+, the 250 and countless others to reduce the amount of treble caused by the clipping. This applied to early transistors, too.

    But in a buffer, there should be no clipping (I haven't measured it but I don't think a guitar can put out 9 V peak-to-peak), so in theory there should be no difference, except maybe in noise characteristics. If the signal is clipped, some say that a FET will sound (or can be made to sound) more tube-like.

    The price issue is important. A single FET may cost you 10 cents. An opamp can cost 10 EUR.
     
  3. Phil M

    Phil M Supporting Member

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    Thank you for the information. Anybody else?
     
  4. nashvillesteve

    nashvillesteve Member

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    I have a Hellbaby, which Bob McBroom described to me a being a vaguely similar circuit to the Jack Orman FET booster design, only with a unique type of gain sound you can add (more "chunk" or "thwack" than "finished product" gain), a mid-range boost and using Opamp instead of FET for a "less harsh top end" or something like that... so the "less harsh top end" might be one piece of info you can draw for your comparison between Opamps and FET...
     
  5. BillyK

    BillyK Supporting Member

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    Steve,
    Ya know, I'd be willing to guess that there's a Germ tranny in the HellBilly. I say this 'cause the HellBilly acts (for me) just like other circuits based on Germ trannys (vintage Fuzz circuits, etc): it wants to be first in line, there's a "metallic" attack to the note that provides it's famous "definition", and other pedals LOVE to have the HellBilly before it (again IMO). These days I am using a Lovepedal Balance which seems to have the same basic characteristics (but better) as the HellBilly, and it's based on a vintage fuzz circuit (I believe).

    I am just guessing here, as both pedals mentioned above are completely hidden from view.

    I probably would have sold my HellBilly by now, but it's a DonnerBox and my 11-year old son (a budding guitarist) just won't let me sell it.
     
  6. nashvillesteve

    nashvillesteve Member

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    The Hellbilly has a Germanium transistor in the input stage and a silicon transistor to stabilize the output stage.

    I really like my LovePedal 1/2 watt amp. I suppose you may get some similar sounds out of your Balance pedal, but it's not really the same thing. The Balance has one knob. The Hellbilly gives you control over output level, gain, and lets you choose over having the circuit sound like a Fuzz Face at one extreme, like a Rangemaster Treble Booster at the other extreme, and all points in between... so, I'm sure it's a great pedal, but doesn't have as much control... I wouldn't really say that they are competing even unless you leave the Hellbilly at one setting only... it works as a boost, a fuzz, a treble booster, etc...

    It kind of irks me that LovePedal doesn't have most of their models even listed on the website. Plus, I don't have batteries in pedals and they all get power from the board, though I suppose if I did get a LovePedal for the board I could run one of those 9V battery clips to the Furman power source or, better yet, to my Pedal Power 2 to one of the outputs with the SAG control so I could lower the power sent to it and make it sound more like a battery....
     
  7. BillyK

    BillyK Supporting Member

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    Thanks Steve. You've got the scoop on the Hellbilly!
     
  8. nashvillesteve

    nashvillesteve Member

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    Cool pedals. Just to be clear, the first description I made about opamps vs. FETs was with regard to the HellBABY, not the HellBILLY... just to be clear.
     
  9. 2x6L6

    2x6L6 Supporting Member

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    Back to the original question, I have to wonder which (op amp v. FET) is most naturally transparent? I have built the Orman mosfet booster and can attest that it is absolutely transparent and natural sounding - a worn out cliche applies - "your amp but louder." It can also goose your amp really nicely and add warm, un-colored gain. So - the fet can be very ampish and tubish. What about op amps?
     
  10. nashvillesteve

    nashvillesteve Member

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    I believe they are similar in transparency except for the top end differences... the Hellbaby is not transparent because of the EQ hump, but that's not because of the Opamp... It's possible that the FET's effects on the top end are a result of combining it with a midrange boost and gain, though, so without that it might be right on par, I'm not sure... I used to have an Orman style booster and it was great until it died (homebrew= soldering errors?)...
     

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