Buffered input to sound card?

Discussion in 'General Electronics Chat' started by Mike33, May 1, 2009.

  1. Mike33

    Thread Starter AAC Fanatic!

    Feb 4, 2005
    Hey guys,

    I record guitar into my PC sometimes, and generally use the mic or line in inputs. Of course, I lose highs due to mismatching, etc. I am thinking a JFET buffer is needed here, easy enough to throw one together.
    Would putting a 4.7V/1W zener diode at the output be a good idea to limit input to <5V to protect the card? In case I use an effect in-line that would boost voltage. And if so, does it matter if the zener goes before or after the output cap on the buffer? In simulation it doesn't seem to matter. Would I need a resistance, or just the zener (not a lot of current here)?
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    Depends on desired sound quality. A single transistor and/or a diode will not give good quality over the entire range without several support components.

    Would need to know input levels, output levels, input impedance, output impedance, bandwidth/cutoffs to start.
  3. russ_hensel

    Well-Known Member

    Jan 11, 2009
    An op amp would make a pretty good buffer. Its power supply can be used to limit the voltage, or a reverse biased diodes to each side of the power supply ( or other reference voltage ) on the output of the op amp will limit the voltage. I would not use a zeener here.
  4. Bailey45


    Oct 27, 2008
    A single stage OpAmp would be the simplest idea. If you power your circuit from a USB connector there is no need to limit the output signal of the opamp
  5. TheBellows

    Active Member

    Jan 18, 2009
    Hi, i use this circuit between my guitar and my computer and i must say it really does magic to the sound quality and it's very simple to build:


    Though i am no expert whatsoever and i have no idea if this is a recommended setup, i haven't blown any equipment yet. :p

    I use SK117 for this circuit.