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third terminal of potentiometer to another input

Discussion in 'Pickups & Electronics [BG]' started by funnyfingers, Oct 17, 2013.


  1. funnyfingers

    funnyfingers

    Joined:
    Nov 27, 2005
    Would sending the third terminal to an amp's second input or another amp's input work? I imagine the second input would be powered on but volume down. The potentiometer would split the voltage between the 2 inputs and possibly not have the problem that a ground would with bleeding the highs.

    I am just curious if I understand what is happening.
     
  2. khutch

    khutch Praise Harp Supporting Member

    Joined:
    Aug 20, 2011
    Location:
    suburban Chicago
    Define "work". The volume control (and I am assuming that you mean connecting the ground terminal of the volume control to another amp or input) will no longer control the volume to any great degree. You would be better off using a splitter cable to just feed the one output to two amps or inputs. That way the volume control would still work normally. Of course maybe this is not what you are talking about at all, your post is a little light on the details.
     
  3. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    What you want is a blend pot. If you tried to use a volume pot to crossfade outputs, there would be a number of issues.

    1. With relatively low series resistance only, it may not be possible to solo an output, depending on the pot value and signal impedance.
    2. Without the parallel resistance of typical volume pot wiring, the taper is going to change.
    3. The nature of varying the resistance of the pot between two sides is also going to change the taper.
    4. The center detent area will yield the lowest output, since the greatest resistance between the signal and both sides exists there.
    5. Most volume pots have a logarithmic taper, which is going to mean very uneven crossfading, as the control is adjusted.
     
  4. funnyfingers

    funnyfingers

    Joined:
    Nov 27, 2005
    I think I have to clarify. I don't mean this as blending between to different amps. I just mean that instead of using ground as ground, you use a path with the same exact impedance. The second amp in this would be on but the master volume would be all the way down. When you turn your potentiometer up the voltage only goes to your first amp, when you turn it down part of the signal goes to the second amp, but you get no volume from that side.
     
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  6. Crater

    Crater

    Joined:
    Oct 12, 2011
    Location:
    Dallas, TX
    If your concern is treble loss as a bass' volume is reduced, there are much simpler solutions (that actually work) than having a second, silent bass rig. Solution 1) Treble bypass capacitor (google it), OR solution 2) internal bass preamp, i.e., an active system.

    Instead of asking cryptic questions about cockamamie schemes, just ask about what you're trying to do: "I'm concerned about treble loss as I turn down my bass' volume, is there anything that can be done about it?"
     
  7. funnyfingers

    funnyfingers

    Joined:
    Nov 27, 2005
    I am not concerned about treble loss though. I want to see if I understand what happens with the audio signal. I would never bring 2 amplifiers with me. I don't even use the volume knob:)
     
  8. khutch

    khutch Praise Harp Supporting Member

    Joined:
    Aug 20, 2011
    Location:
    suburban Chicago
    If I understand what you are saying there is no need to use a second amp, just solder a 1Meg resistor from the "ground" pin on the volume pot to ground. Same result. When you turn the volume all the way up you get full volume. When you turn the volume pot all the way down you get about 2/3 full volume. Is that what you want?
     
  9. line6man

    line6man

    Joined:
    Jun 20, 2008
    Location:
    Close to Los Angeles, CA
    I have absolutely no idea what you're getting at now.
     
  10. drewfx

    drewfx

    Joined:
    May 14, 2009
    It sounds to me like the OP is just exploring the idea of a virtual ground.
     
  11. P Town

    P Town Guest

    Joined:
    Dec 7, 2011
    I don't understand what you are trying to describe. Can you post a diagram?
     
  12. megafiddle

    megafiddle

    Joined:
    May 25, 2011
    You are sort of describing a panning circuit, with one amp as "left" and one amp as "right", but with the "right" amp off.

    You can't use an amp input as a substitute for ground, though. It is high impedance - 500Kohm or 1 Megohm.
    You need the ground as it is a source of "zero signal" at a very low impedance.

    Also it is not the presence of the ground that causes treble loss to begin with. It is caused by the series
    resistance that the pot adds into the circuit when it is not at "10". When this is combined with any
    capacitance in the following part of the circuit, it forms a lowpass filter.

    -
     
  13. funnyfingers

    funnyfingers

    Joined:
    Nov 27, 2005
    This makes sense, I just thought, as someone else said earlier, that the other amp would be a virtual ground and the path would be exactly the same so the voltage would split identically unlike it does with a ground where you don't turn down the volume equally over the full frequency range.

    Thanks!
     

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