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

Thread Starter


Joined Nov 14, 2008

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,

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.


Joined Dec 20, 2007
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.


Joined Jul 17, 2007
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.