Need help with guitar buffer circuit...

Discussion in 'The Projects Forum' started by jeghers, Nov 14, 2008.

  1. jeghers

    Thread Starter New Member

    Nov 14, 2008
    You folks who know electronics, please advise me! I am wanting to design some buffer circuitry for a homebrew fancy guitar selector gadget. I know that op-amps will give me more flexibility in circuit design over JFETs, but some people have observed that op-amp buffers sound "colder and more sterile".

    Do you have any opinions? Would a JFET circuit really preserve the guitar's tone better? If there is a difference that could be noticed, I think I'd be willing to do the more involved JFET design, though I'll need to know how to boost the gain (I'll want to boost the signal be a few db), which of course op-amps can do more easily.

    Also, seems to me a JFET circuit might consume less power than using op-amps -- Agree? Disagree?

    I know this is a rather ethereal question, but if any of you know about this, please advise.

  2. DickCappels


    Aug 21, 2008
    Bipolar or FET, I doubt you can hear the difference, the selection of circuit should depend on what you want the amplifier to do to the signal. If you want the amplifier to just reproduce the input waveform, only with a higher amplitude, you can find many excellent FET and bipolar op amps around that will do the job. If you want the sound "colored" then you can accomplish that by selecting a poor amplifier, intentionally reducing loop gain, or design it effects such as freqeuency coloration or distortion with carefully designed circuits around the opamps.

    The OP reminds me of distant discussions of the vacuum tube's superior liquidity (not the kind of liquidity people talk about in the news today) compared to the transistor, or the benefits of velocity matched monster cables (tm). If you cann't measure it, you cannot hear it.
  3. jeghers

    Thread Starter New Member

    Nov 14, 2008
    My goal is that I do not want to color the guitar sound. I am designing a switching device (to select multiple guitars) that includes gain control (with the ability to boost a few db). Later devices will color the sound, so I want this device to ONLY select which guitar without changing the tone. The point of the buffering is A) to present a high input impedance to the guitars so their passive pickup/tone circuits are not loaded down and colored in any way and B) low output impedance to drive the amp/pedal that it feeds into really well.
  4. bertus


    Apr 5, 2008
  5. mik3

    Senior Member

    Feb 4, 2008
    JFETS or generally transistors are non-linear devices so they will distort the actual tone if the circuit is npt designed properly. Whereas, op-amp are very linear devices with negative feedback applied via a single resistor. In my opinion op-amp will be easier to deal with and control the gain. If you choose high quality op-amps you will get good results.