Help me out making a simple mixer

[Transmogrifox]

I recommend reading about op amps and the DC summing amplifier that is common to all of these mixer designs.  It appears this thread includes some bad information that could be confusing for a newbie...especially the part about soggybag's original design not doing anything.  His original plan will work relatively well even though there are more elegant ways to do it.

My opinion is the hard-copy scan of "Microphone Mixer" comes the closest to what you want as a balance of high input impedance and simplicity.  All you would have to change in that circuit is the power supply configuration with regard to DC biasing to make it work on a single-sided 9VDC source.

I think there is little merit to this "inverting/noninverting" stompbox design concept.  It makes about as much difference to the sound of the guitar itself as playing your guitar upside-down (neglecting the added difficulty to the musician).

Other than an emotional feeling you get from knowing your stompbox is "non-inverting" there is no audible difference.  Any possible advantages are outweighed by the fact that you have added noise by adding a second inverting op amp stage.

In the commercial industry this makes sense.  You don't know how the musician is going to re-troute the signal to/from a mixer.  If you have the signal split into two paths processed separately and mix them together in the end, there can be a problem if there is an inverting effect in one of the paths, but not the other.

[soggybag]

Thanks for the replies. This is all good info. I'll have to try this out and see what happens. I'm trying to make a box with an octave up and an octave down. I want to mix the original signal with these.

[Projectile]

Are you just mixing two signals? If so, Sean's B.blender, Miniblender, or Joel's Buff'N Blend would probably be easier solutions. I use them to mix in clean signals with effects all the time. They work great!

[soggybag]

I looked at the blenders. They are pretty simple and were giving me some good ideas.

I was trying to keep things as simple as possible by keeping the parts count low. So my idea was to use a dual op-amp. One op-amp for the input buffer and one to mix the three signals (if possible).