[sdiy] mixer with effect send

[Scott Bernardi]

Tim has pinpointed the problem - no resistor between the pot wiper and
the inverting input of the buffer amplifier. Think of it this way: The
effects send opamp is configured as an inverter, which means the
inverting input is at virtual ground. So you are running the Send pot
wiper into ground.
I've got a mixer design I've done recently. It's a bit in the
preliminary stage - I've breadboarded a channel and etched a PC board,
but haven't wired it up yet. Take a look:
http://home.attbi.com/~sbernardi/elec/og2/ultra_mixer.pdf


Tim Ressel wrote:

> Daryl,
>
> Your basic approach looks sound. I am a bit concerned
> that there are no resistors between the wipers of the
> 'send' pots and the summing node of the 'fx send'
> opamp. Also you have two pots stacked up on the 'fx
> send' path. My rule of thumb for series unbuffered
> impedances is: 10 to 1 ratio. In other words, if the
> first pot is 10K then the second pot should be 100K.
> It looks like in your circuit the pots are going to
> act somewhat odd and not track as you would expect.
>
> It would help if we knew how it was not working...
>
> --Tim Ressel
>
> --- daryl groetsch <synth_dg at yahoo.com> wrote:
> > I've looked and cannot find a schematic for a mixer
> > with effect sends. I'm building one, but the sends
> > are
> > not working. Perhaps someone wouldn't mind looking
> > at
> > my design and telling me what is wrong with it.
> > Thanks
> > a lot in advance!
> > Daryl
> >
> > here it is:
> > http://www.angelfire.com/droid/a/mixer.jpg
> >
> > =====
> > http://www.darylgroetsch.com
> > noise, schematics.
> >
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