Single vs Double Op-Amp

[Bio77]

I'm looking Ibanez chorus schematics.  For the gate part of the circuit in some versions they use a single op-amp (UA741) and in later versions only one op-amp from a dual op-amp package (4558).  Made me wonder why single op-amp packages even exist ?    Are there any instances when a single op-amp package has an advantage? 

[mjg]

I think the single op amps have other functions on the other pins, but we tend not to use them in pedal circuits. Pins 1 & 5 do something.  Not sure what!

[matmosphere]

I also think part of the answer is that single opamps came out earlier. I just did a little googling and it sounds like single opamps go back to the 40's and used tubes (how have we not gotten into discrete tube op-amps). Single opamp IC's came out in the mid-sixties. Dual opamps seem to have not shown up until sometime in the 70's, but I can't find much info on exactly when, probably owing to the fact that the innovation seems to have been happening with single opamps, which kind of makes sense.

I suspect cost was a major factor too. I read something about one of Wildar's early opamps cost $300 a pop in the mid-sixties, which is nuts compared to what we pay, especially if you convert that to today money. I'm guessing that dual opamps were far more expensive than singles until somewhat recently, so from a cost standpoint it may have made sense to use to singles instead of one dual. As I recall from my childhood electronics weren't small. There would have been plenty of room for the extra IC and a couple other parts.

[Bio77]

I expected the answer was going to be something with those other pins, but I haven't run across them being used in any schematics.  It's a nice surprise that I'm not the only one that doesn't know!

[zombie_rock123]

Doesn't the Earthsound Graphic Fuzz use some of the old single opamp pins? Could be way off here though

[alanp]

Sometimes you want two singles instead of one double. The first thing that springs to mind is when one opamp is part of the LFO section, the other is a gain-y part of the audio section, and in proximity, the LFO opamp can be heard in the audio output (TICKTICKTICKTICK).

The other time is when it plain-out makes the physical PCB layout easier and cleaner.

[Aentons]

I think the opamp standard 8 pin packaging came from transistors, and transistor packages came from octal tubes being more common. The extra pins on singles were used for correcting input voltages (offset null) which was due to poor manufacturing tolerances when the stuff was new. Once manufacturing got better, "they" didn't need those corrections anymore and were able to use those pins and started making dual packages. Its why there is not a dual lm308.