Question about dual opamps

[arawn]

I was doing some research as preparation to my next build, and i got to wondering if you could use the noninverting amp in one stage and the inverting amp in the other of a dual opamp and if so what would it sound like?? Is this something of use or is it pointless to pursue??

[bkanber]

Try it! I don't think anything special is going to happen.. If you set up op-amp A to non-invert, and then just have the second stage in series to inverting op-amp B, I don't think anything special will happen.

However, if you invert and non-invert in parallel, ideally you'll get fully destructive interference, and silence will come out.

If you invert and non-invert in parallel, and one of the branches has a cap in it, that branch should get a 90 degree phase shift (depending on frequency-- there's a narrow range where it won't be 90 degrees. Study up on Bode plots, I don't remember this stuff too specifically), giving you a total 90/270 degree phase shift. You might get a phaser type effect. Whether or not it'll be noticeable or not, I have no clue.

Best thing to do is just try it! Worst thing that happens: you waste 10 minutes

And, of course, I could always be wrong about everything I just said. You might want to wait till someone smarter replies

Burak

[slacker]

Look at the Marshall Guvnor or Shredmaster they use one non inverting and one inverting stage with one pot to control the gain of both stages.

[Mark Hammer]

Using one opamp in inverting mode and the other in noninverting mode can produce some phase issues, but there are so many instances where it doesn't matter, that you should consider this as largely a nonissue unless you are running in stereo or sending a feed to the board from a different point in the signal path.  Where you will most likely notice the impact of using the two halves in different mode is with respect to changes depending on how you set gain.  In inverting mode, gain goes up as input resistance gets smaller, and as feedback resistance gets larger.  In noninverting mode, gain goes up as feedback resistance increases and as resistance from inverting pin to ground decreases.  The Bluesbreaker makes use of those differences by using a single pot to simultaneously increase the feedback resistance of one stage and decrease the input resistance of a second stage.