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ISO: Op-Amp Boost-Only Design

Discussion in 'Effects [BG]' started by EricssonB, Dec 20, 2013.


  1. EricssonB

    EricssonB

    Joined:
    Apr 5, 2011
    Location:
    CoSpgs, CO.
    I'm searching for a schematic/layout for a *transparent boost-only circuit based around an op-amp. I tried a of couple transistors-based circuits, but they weren't performing as I was expecting. The last build had its guts ripped out and is now a passive attenuator with a 500k ohm pot, dimming LEDs and 3PDT wiring -- love it for guitar.

    I've got packs of TL0XX op-amps sitting around, so if I can chuck one on a board, that'd be swell.

    Know of any? I've searched around, but didn't find what I was looking for.


    *as transparent as possible.
     
  2. dune2k

    dune2k

    Joined:
    Sep 26, 2009
    Location:
    Germany
    MXR Microamp.
    Put in electrolytic caps that are rated for 18V+ and run it at 18V. Doesn't get more transparent than this.
     
  3. MagicMan_841

    MagicMan_841 Supporting Member

    Joined:
    May 29, 2005
    Location:
    Ithaca, NY
  4. Crater

    Crater

    Joined:
    Oct 12, 2011
    Location:
    Dallas, TX
    Is your google broken? :) I found this pretty quickly, it's a minimal parts count op-amp buffer.

    http://www.jer00n.nl/2010/07/28/clean-boost-for-guitar-or-bass/

    I'm sure it will work fine as drawn for bass, but if you're concerned about bass rolloff you could substitute a 220nF cap on the input for the 100nF that's specified. If you're OCD about "tone" you might want to put in non-polarized 10µF electrolytic caps in place of the standard polarized electrolytics. I would also add power supply filtering and a polarity protection diode if this is going to be built into a stompbox.
     
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  6. EricssonB

    EricssonB

    Joined:
    Apr 5, 2011
    Location:
    CoSpgs, CO.
    My Google is only partial; I'm at work and the best websites are blacklisted.

    Thanks for the links, guys. I'll go through this list when I get home -- none of these damned links work here. :rollno:

    I am concerned about frequency loss, so I'll be considering those mods.

    This one seems to work! Yeah, same website, but .com instead of .ca works.
    http://tagboardeffects.blogspot.com/2013/03/mr-black-boost-tiger.html
     
  7. mrbell321

    mrbell321

    Joined:
    Mar 26, 2012
    Location:
    N. Colorado
    I recommend looking at the datasheet for whatever op amp you plan on using. There is usually a reference schematic in there that will be minimal parts and very transparent. You might need to change some of the caps for the right frequency range, but it'd be a good place to start.
     
  8. dune2k

    dune2k

    Joined:
    Sep 26, 2009
    Location:
    Germany
    If you don't have a way to run pedals at 18V, try getting your hands on an ICL7660S or a MAX1044 and slap them in there used as voltage doublers (schematic can be found on the net, e.g. in their datasheets).

    You don't need non-polarized caps in there btw, good polarized ones will do the trick as well, although using a non-electolytic 1uF cap on the input would work just as well. I doubt one can hear the difference between those (1uF, 10uF, polarized/non-polarized/non-electrolytic) though.
     

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