A Question About Noise-Gates and Bias Controls on Fuzzes

Discussion in 'Effects [BG]' started by 420 Bass It, Jan 30, 2018.


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  1. 420 Bass It

    420 Bass It

    May 29, 2017
    Henlo.
    I am a sucker for gated fuzz, and recently I'm seeing more and more pedals that have a bias control, or a voltage starve control which can get that broken-up sound that I like.
    I also saw a video of Brian Hamilton of SS/BS on Pedals&Effects saying that a bias control acts like a noise-gate when it's used to voltage-starve.

    My question is - does lower voltage = gate? I really like gated fuzz and I really like bias controls so it'd be really good to know.
    :hyper:
     
  2. boomertech

    boomertech Frank Appleton Commercial User

    Apr 8, 2009
    Syracuse, NY
    Designer/Owner of FEA Labs
    No, lower voltage does not make a gate.

    There are two types of "gates" that people refer to. The first type is when the signal level breaks over a threshold and that portion of the signal is amplified. It will give a "sputtery" sound as the volume level trails off, because the portions of the signal below the threshold are removed. You see this type in fuzz pedals.

    The other type of gate is when the signal envelope has crossed a threshold. This type of gate does not remove portions of the signal... it allows the entire signal to pass until the envelope of the signal falls below the threshold, then it prevents any signal to pass. This type of gate is used in noise gates to keep background noise to a minimum.

    -Frank
     
    Driven Crane likes this.
  3. Are the two sometimes used in gated fuzzes? Or is it if the first type is applied “hard enough” (thinking ones where the gated aspect is on a knob) that it then decays into the second type of gate and barely lets any signal through.
     
    boomertech likes this.
  4. boomertech

    boomertech Frank Appleton Commercial User

    Apr 8, 2009
    Syracuse, NY
    Designer/Owner of FEA Labs
    Maybe, there are just too many fuzzes to know what they all are. :thumbsup:

    But the first type of gating can have a knob to set the threshold. A lot of times the gate knob sets the bias on transistor to create this threshold that the signal must overcome before being heard. So there is a point where the signal will be so small that barely any signal gets thru. I can't recall any fuzzes that use both types of gates or even a fuzz with the second type of gate. The second type of gate is usually found in noise gate boxes.

    -Frank
     
  5. Being and Bass

    Being and Bass

    Apr 9, 2017
    Canada
    boomertech has it right; the "gated fuzz" effect is just from starving the circuit to the point where it cannot amplify a signal through its circuit and so the sound quickly dies. The effect can be similarly achieved by placing your fuzz pedal in a noise gate, with threshold and release set properly, but it will never sound the same.

    I have a fuzz in my gate right now, but have a Germanium fuzz en route with a bias control because the erratic clipping a starved circuit produces a mind of its own. Putting a fuzz in a gate, or using a fuzz with a gate (like the EHX Deluxe Muffs) didn't do it for me. It's worth having the separate pedal for just this effect if you really use fuzz.

    (Fyi, I also have the Russian Muff in my power supply on a variable circuit, currently getting about 5.5V. It works quite well, but the older germanium circuits do it so much better. I look forward to the muff being fill bore again and the Germanium to take care of the clip.)
     
  6. boomertech

    boomertech Frank Appleton Commercial User

    Apr 8, 2009
    Syracuse, NY
    Designer/Owner of FEA Labs
    I never said anything about "starving the circuit".

    -Frank
     
  7. Being and Bass

    Being and Bass

    Apr 9, 2017
    Canada
    Sorry, I shouldn't paraphrase or use other terms. Cheers.
     
  8. boomertech

    boomertech Frank Appleton Commercial User

    Apr 8, 2009
    Syracuse, NY
    Designer/Owner of FEA Labs
    Lowering the voltage is referred to as "starving" the circuit. What lowering the voltage does is reduce signal headroom within the circuit and can change the biasing of transistor circuits so that the signal is operating on a different part of its transistors function curve. Usually a designer will specify an operating voltage and bias the circuit within that voltage for maximum un-clipped gain or for the most linear signal amplification. When you over-bias or under-bias a transistor amplifier circuit, you move the operating point closer to a voltage "rail" so that clipping occurs unevenly to one side of the signal before the other. The transfer function of a transistor isn't linear, so changing the bias point can really alter the signal linearity (non-linear distortion). You can also bias a transistor amplifier operating point outside of the range of the transistors transfer function curve. So some transistor designs can be "starved" to this bias point that might cause that sputtery gating effect, because only the parts of the signal that are large enough to cause the transistor to forward conduct and amplify will be heard, the parts of the signal that are too small to cause the transistor to conduct will be lost and not heard.

    Circuits with opamps will still have less headroom when you "starve" it, but usually these circuits will continue to bias properly. That is until you reduce the voltage to a point beyond the operating parameters of the opamp... then there can be circuit havoc.

    Even though "starving" the circuit may affect the bias of transistor circuits, it does not mean that they will all have a gating effect from it. For the other type of gate that is used on signal envelopes as a noise gate, a "starved" circuit would be a bad thing. Since these gates are designed to be as clean as possible for the signal.

    You will have to test for yourself if starving a pedal makes the sounds that you like or not.
    Only starve analog pedals.:thumbsup:

    -Frank
     
  9. 420 Bass It

    420 Bass It

    May 29, 2017
    Ah, but that does mean the signal is "gated", right?
    I mean, there would theoretically be no hum or hiss or any unwanted noise.
     
  10. boomertech

    boomertech Frank Appleton Commercial User

    Apr 8, 2009
    Syracuse, NY
    Designer/Owner of FEA Labs
    If the signal in a gated fuzz or the signal envelope in a noise gate are small enough to be blocked then the hum and hiss shouldn't be heard. That's the goal of noise gates, but I don't know if all fuzz pedals go silent when the signal is gated.

    -Frank
     
  11. smllsnd/bigsnd

    smllsnd/bigsnd Commercial User

    Mar 18, 2009
    philadelphia, PA
    owner, smallsound/bigsound
    i don't remember the exact quote but i was referring specifically to the mini where it sputters out and becomes gated when the bias is turned down (basically what frank fea says below), not for all effects.

     
    bassvirtuoso likes this.
  12. 420 Bass It

    420 Bass It

    May 29, 2017
    So if I starve the voltage on a fuzz pedal with a bias control, that means there wouldn't be any hiss, right?
    For example, when the Mini is under-biased, or in this video:


    Around 5:17, the pedal is used with low bias and there is a gated effect. However he doesn't stop playing for long enough for me to listen if there is actually no hum. If pedals with a bias control can get rid of hiss it would be a great thing for me :bassist:
     
  13. smllsnd/bigsnd

    smllsnd/bigsnd Commercial User

    Mar 18, 2009
    philadelphia, PA
    owner, smallsound/bigsound
    it's not a simple black and white answer as sometimes starving a pedal of voltage creates more hiss, completely changes the timbre or character of the signal or doesn't do any of the above. it really depends on the circuit and *how* it is being starved of voltage. for example, in the case of the mini, the bias control changes the voltage in only part of the circuit, thus affecting the bias point of one particular transistor. it would work very differently if one of the other transistors were being starved or if there were a global function affecting the entire circuit.

    also, i haven't played a carcosa so i can't accurately comment on how it reacts but it sounds fairly gated in that setting you posted.
     
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  14. 420 Bass It

    420 Bass It

    May 29, 2017
    Oh okay. Thanks Brian and Frank! I understand it much better now:hyper:
     
  15. boomertech

    boomertech Frank Appleton Commercial User

    Apr 8, 2009
    Syracuse, NY
    Designer/Owner of FEA Labs
    Are you calling the bias knob a "starve" knob? Or are you asking if you starve the power supply voltage to a pedal that has a bias control knob?

    A bias knob isn't always a starve knob. A bias point is where the DC operating a voltage is set, that DC operating point can be changed with a control if the designer has made that a function for the user to change... but changing that DC operating point is not a "starving" of the circuit voltage.

    As mentioned above, when you globally "starve" the pedal circuits by reducing the supply voltage a lot more than a possible "gating" effect can happen. Gating, biasing and starving the power supply are all very different things... they may interact with each other or they may not... the easiest way to tell is to test them.

    In that video there was no "starving" of the supply voltage, only a bias adjustment with the AFTER knob. It too sounded to me like it created a strong gate effect.

    -Frank
     
  16. smllsnd/bigsnd

    smllsnd/bigsnd Commercial User

    Mar 18, 2009
    philadelphia, PA
    owner, smallsound/bigsound
    yeah good point by using quotes around starve in general. changing voltage on a particular parameter isn't necessarily "starving" the circuit in any way, it's just changing a voltage. that being said, i understand how it is easy to think of it in that way though as a user. for example, i have a "starve" control on one of my pedals (buzzz) where it isn't necessarily doing *exactly that* but sometimes a control name for a non-standard or non-linear control can provide a simple reference point for a user.

    like you said, using your ears is usually the best way to figure out what something is doing! :smug:
     
  17. 420 Bass It

    420 Bass It

    May 29, 2017
    That's a good distinction to make... It's all much clearer now

    Lol yep, truth is I'm a fan of your pedals and I've watched videos about the buzzz and that's how I picked up that bad habit.

    Thanks for the replies ;)
     
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