At the behest of Robert Rich, I built a triple reversing+bias module to
his specifications. Each stage provides -/+ 5V bias in the absence of a
jacked input, and as each output is used, it is removed from being summed
with the next stage. All stages have a gain of -2 to +2. Thus you have a
3-to-1 mixer, or a gain stage with bias, etc. Formulaically:
2.500V
|
IN_A ∗ (-2 to +2) = OUT_A
|
2.500V |
| |
IN_B ∗ (-2 to +2) + OUT_A = OUT_B
|
2.500V /------/
| |
IN_C ∗ (-2 to +2) + OUT_B = OUT_C
The dashed lines indicate the normalling jack switches for bias
reference and the section cascading.
With thanks to Stooge Larry, I even have a nice panel for the
prototypes:
http://www.oldcrows.net/~oldcrow/synth/crow/3xrevmix_ft.jpghttp://www.oldcrows.net/~oldcrow/synth/crow/3xrevmix_bk.jpg Looking around the web afterward, I noticed that Stooge Moe almost built
the same thing. This one is a bit different, though. And is also quite
different from an Oakley Multimix.
I was pondering making a run of PC boards, and selling those along with
three 250K type 149 pots for those interested. (I got this stash of 149s
from a former workplace and decided to do something with them, thus this
1U module. ;)
Crow
/∗∗/