replacing 2 single opamps (buffers) by a dual opamp?

Started by add4, February 20, 2012, 01:59:36 AM

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add4

I'm working on a pcb design for the great cheddar.
I interpret this circuit as an input buffer (opamp) going into a fuzz face like stage going into a tone stack then the rotary switch selects options on tone and transistors bias et there's an output opamp based buffer.
my question is:
can i replace the 2 buffers (single opamps) by 1 dual opamp?
i guess it's pretty standard and i can do it, but then i don't understand why RG didn't do that in the first place. or is it a question of keeping the unit original? then why love tone wouldn't do that? i don't see the point of using 2 single opamps ...
can anyone explain that for me?

DavenPaget

First : feasibility , like when you're perf-ing sometimes 2 single opamps is good .
Second : Maybe keeping it original ?
3rd : There's no problem replacing 2 single opamps with 1 dually . Totally not a problem .
Hiatus

add4


R.G.

Quote from: add4 on February 20, 2012, 01:59:36 AM
can i replace the 2 buffers (single opamps) by 1 dual opamp?
i guess it's pretty standard and i can do it, but then i don't understand why RG didn't do that in the first place. or is it a question of keeping the unit original? then why love tone wouldn't do that? i don't see the point of using 2 single opamps ...
can anyone explain that for me?

My PCB layout approach is to put in the parts you can't change (i.e. switches, physical mounting, PCB mounted controls, etc.) first, then put all the rest around the things that can't be changed. In this layout, I started with the rotary switch as the central physical requirement to eliminate hand wiring of the switch.

That being done, it was more expedient for trace routing to put in two singles than one double because the traces to one or the other section of a double would have had to be much longer. I like traces to opamps to be as short as they can possibly be to eliminate as much as possible any stray signal coupling and crosstalk.

There was a competing design. I thought about using two doubles, and neutering half of each one. It turns out that the cost of a dual opamp is about the same as the cost of a single, so in most designs I use only duals, even if I only need one. A slightly different rule makes me use two duals instead of one quad. The output orientation on quads are on all four corners, so the signal flow is always center-out. In most layouts, having all the input to output flow in one direction instead of two is simpler and easier if the inputs-output flow is in one direction across all packages.
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

add4

Indeed i read that about the traces length in your book RG :)
That's a perfectly answer to my question, thanks to you all for helping