Need help selecting and LOCATING the best op-amp for guitar audio

Discussion in 'The Projects Forum' started by jeghers, Nov 17, 2008.

  1. jeghers

    Thread Starter New Member

    Nov 14, 2008
    7
    0
    All,

    I am designing a 3-way guitar selector switch with gain controls for all 3 guitar inputs. It will use op-amp buffering and is meant to NOT affect or "color" the tone of the guitars in any way.

    Here is my problem: I have identified what I *think* is a good candidate for a very high quality op-amp (OPA132). But I am not completely certain it is the best pick, and I am also having trouble finding it in a DIP package.

    Most web pages discussing good audio op-amps are geared towards headphone amplifiers, which is not quite the same application as what I am doing. An op-amp well suited for that use might not be best for mine. I just don't know.

    I am also bothered by the fact that the dual and quad packages have some diminished performance numbers, so I might be pressed towards using more single-unit 8-pin DIPs.

    So my question is this: what is the best op-amp for low-distortion, no tone coloration, good low-power & (maybe) low-voltage performance, and overall stability? And also very important: WHERE CAN I GET IT IN A DIP PACKAGE??? The OPA product line seems to be only sold in SOIC packages now...

    Thanks for any and all help,
    /Mark

    ps Here are my design goals:

    - 3 guitars in, one low impedance output to a pedal/amp/whatever.
    - Op amps allow high impedance guitar inputs so guitar tone is not adversely affected.
    - The device is meant to NOT affect or "color" the tone of the guitars in any way.
    - Each guitar input has a gain control (e.g. a volume knob) with a gain somewhere between 3 and 12 db (I've not decided how much yet).
    - It will use non-popping (debounced) solid-state switching with CD4066 analog switches.
    - Powered by either external or battery. I am willing to design for 2 9v batteries, but I'd prefer just one 9v battery if I can get away with it. So power consumption is important bt not paramount.
    - Some digital logic (with capacitor-debounced Schmidt triggers will provide with exclusive (1-of-3) or multiple (more than one combined) guitar selection.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    I think a LF351 will suit your application. If you visit www.national.com you find more.
     
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    An OPA134 single, OPA2134 dual and OPA4134 quad opamps are the same as the OPA132 except they are available. They are available in DIP packages at Digikey.

    You won't be able to measure or hear any difference if you use single opamps or dual or quad opamps.

    The LF351 is much noisier (hissss) than the OPA opamps.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Digikey, Mouser, Newark and Jameco all have the OPA2134PA (8-pin DIP) in stock, but the OPA4134 in DIP is scarce as hen's teeth. Digikey carries it in the SOIC package, if you can deal with surface mount.

    I suggest that you not use DIP sockets; sockets will add noise.
     
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