Opamp Q. Why those ones?

[psiico]

Is there any particular reason why the majority of effect schematics I see tend to use the same few opamps?  Are they somehow better for our applications or are they just cheap and readily available?  Is there any reason not to experiment with opamps I find in old electronics on the side of the road?

I found a 4 deck tape dubbing machine at the side of the road on the way home from work tonight, didn't even test it to see if it worked, lol.  It's got a bunch of opamps in there, I can always just test them with sockets or on a breadboard.  According to the datasheets a few of them are high quality audio, low-noise types, should be useful for some things.  The best part, they are all socketed. 

[brett]

Hi.
Some op-amps are just superior critters.
Take the TL071/72/74 series.  Extra high input impedance (JFET inputs), low noise. reasonable power consumption, and they can drive a fair load.  They are not quite rail-to-rail devices, but they go close.  That's why you see them in lots of designs.
In general the older 741 and 4558 chips aren't up to scratch (tho some folk still put 4558s in tubescreamers, but probably not for tone).

cheers

[markm]

I'm gonna fess up and admit that I kinda like the sound I have gotten from some of my 741 builds.
I like the not-so-perfect performance in say the OD-250.
   MM

[Sir H C]

Also have price, ubiquity (easy to second source), and for some things/places they have big set of testings to verify that the parts are up to their standards and it is a time consuming process to get the part to be certified (worst for medical industry).  So why bring something new that you have to get checked out when you can use something already okayed.

[burnt fingers]

I'll second the 741's.  I have em in my modded tube reamer and the high gain overdrive/distorion I just finished.  I tried a bunch of chips. lf351's Tl071's etcc.. but I like the 741 for distortion.  I agree though that the same few apprear time after time in effects becuase they sound good.  Get yourself a handfull and try em in a socket.  See what you like. 

Scott

[Mark Hammer]

Is there any particular reason why the majority of effect schematics I see tend to use the same few opamps?  Are they somehow better for our applications or are they just cheap and readily available?  Is there any reason not to experiment with opamps I find in old electronics on the side of the road?

I found a 4 deck tape dubbing machine at the side of the road on the way home from work tonight, didn't even test it to see if it worked, lol.  It's got a bunch of opamps in there, I can always just test them with sockets or on a breadboard.  According to the datasheets a few of them are high quality audio, low-noise types, should be useful for some things.  The best part, they are all socketed. 

First, nice score!

Second, the overwhelming majority of op-amps are designed to address different operating conditions, rather than for sound.  So, some are designed to keep current consumption low.  Some are designed to handle large supply voltages, where others are designed to accommodate changing (or very small) supply voltages and still maintain performance.  Some are designed to be able to see very low-impedance loads at their output.  Others are designed to happily accept very high impedance loads at their input.  Some are designed to provide very little error/offset.  Others are designed to be able to provide very fast and wide voltage swings.  Some are designed to be compensatable for special needs.  In short, they are all something that the manufacturer has invested time and money in developing because they fill a niche that other concurrent products of their own or competitors do not fill.  That is why you can look in a Mouser/Maplin/Jameco/Jaycar/Digikey/Electrosonic catalogue and see so many different kinds: because they all address different needs so they are all worth carrying.

As it happens, the supply voltage and bandwidth needs of the majority of pedals are pretty darn similar.  Pedals that run off 9v batteries and process guitar signals have fairly common needs as far as op-amps go, so you will tend to see the usual suspects being mentioned.  Keep in mind as well that higher-end op-amps are intended to reduce error under a broader array of circumstances, and much of what we crave as guitarists IS op-amp error.  We call it coloration and tone.  Where there already IS a predefined coloration/tone that one wishes to preserve, then certain op-amps will be important in helping to achieve that.  As I hasten to regularly remind folks, though, what sounds good for processing a single instrument in making music is not necessarily the same thing as what will sound good in reproducing music that is already made.  So, $6 op-amps may be eactly what you need to listen to music that involved pedals using fifty-cent 4558s, but 4558s were what you needed to make those sounds in the first place.

Beyond that, you are correct in assuming that the same ones keep cropping up because:
a) they're good enough
b) they're easy to find
c) they're cheap enough
d) people will already have some lying around