owlexifry
Well-known member
- Build Rating
the short story behind why this pedal was built involves the bass player of my band finally letting go of his helix stomp and agreeing to try/use another analog bass driver/distortion.
he’s already got a sansamp bass driver, but apparently that’s not quite doing it for him, so i suggested this board/build from aionfx.
tbh all i really know about darkglass pedals is there’s been a lot of hype for them with modern rock/metal oriented bass players, and supposedly this one (& the alpha omega) was designed in collaboration with the Karnivool bassist. i guess that’s good?
So this is is my first proper bass pedal build.
with regards to the opamp selection, this is discussed in the Aionfx build doc:
The original Alpha Omicron uses the MC33178 for IC1 and IC3-7. This op-amp is a favorite of Darkglass,
used in nearly all of their pedals in some capacity.
For the Omega/Omicron circuits in particular, the the distortion comes from overdriving the op-amps
directly, so selection is important, and different op-amps may have wildly different characteristics when
overdriven.
The 33178 is an older op-amp, still readily available in SMD format but nearly impossible to find in DIP.
We cross-referenced datasheets for dozens of different audio op-amps and found that the RC4559P is a
near-exact match.
It could be the case that they are truly identical and that the slight differences are due to different
measurement techniques between ONSemi and Texas Instruments. But either way, it’s very close in the
ways that matter—slew rate, noise figure, and gain-bandwidth product—and in our testing it sounded
the same.
Despite being an avid bass player in my high school years (before i grew a much stronger interest in playing guitar) I had never really geeked out on bass gear in the way I have with guitar, so tbh i’m completely out of the loop, i don’t really know much about bass gear other than typical hardcore/metal oriented applications involving sansamp bass drivers, ampeg gear if you’re lucky, musicman stringrays are awesome, and for DAW recording - running dual tones with clean sub / dirty parallel channels for good results (with line6 pod farm2 - yes i still use it
), and also glancing at all the different offerings/demos from Sushi Box gear, entering a whole other world of bass things i don’t really understand.
so i guess that’s a lot of words to descibe how it’s quite satisfying to build and try something from a completely fresh perspective, ie. a modern bass driver.
In my completely uninformed opinion - I think this sounds heckin awesome with my Squier VM P-Bass (although running into an SLO100 clean channel and 4x12 guitar speakers)
- The 'mod' control is described as sweeping between 2 different distortion circuits - 'alpha' and 'omega' apparently. And it does sound like that - appears to sweep between vintage and modern inspired channels, and they sound distinct enough to warrant blending.
looking at the schematic it would mostly appear to be sweeping between x2 different EQ/filter pathways that look quite similar, with one having an additional fixed gyrator filter.
- 'blend', and 'drive' are fairly self explanatory.
- the 'level' control is not a master volume. it's peculiar in this case that it follows directly after the 'mod' control, and before the blend.
so really, the level control, being the 'distortion level' i guess, behaves as another blend control. despite how weird this is (to me at least), it actually works really well to foster a wider variety of tones/textures with the blending.
- the bass toggle ('growl' per darklgass), switches a 68n in parallel with a 22n coupling cap not far after the input buffer. good feature. i like it toggled on.
- the high mid toggle ('bite' / 2.8K per darkglass) appears to be a 'presence' boost in the EQ range as described. Still undecided on this, but it works well.
so despite having no master/output control (which doesn't seem to matter) it's a brilliant little package that makes your bass sound beastly with as much or as little drive/colouring as you want.
Demo:
he’s already got a sansamp bass driver, but apparently that’s not quite doing it for him, so i suggested this board/build from aionfx.
tbh all i really know about darkglass pedals is there’s been a lot of hype for them with modern rock/metal oriented bass players, and supposedly this one (& the alpha omega) was designed in collaboration with the Karnivool bassist. i guess that’s good?
So this is is my first proper bass pedal build.
with regards to the opamp selection, this is discussed in the Aionfx build doc:
The original Alpha Omicron uses the MC33178 for IC1 and IC3-7. This op-amp is a favorite of Darkglass,
used in nearly all of their pedals in some capacity.
For the Omega/Omicron circuits in particular, the the distortion comes from overdriving the op-amps
directly, so selection is important, and different op-amps may have wildly different characteristics when
overdriven.
The 33178 is an older op-amp, still readily available in SMD format but nearly impossible to find in DIP.
We cross-referenced datasheets for dozens of different audio op-amps and found that the RC4559P is a
near-exact match.
It could be the case that they are truly identical and that the slight differences are due to different
measurement techniques between ONSemi and Texas Instruments. But either way, it’s very close in the
ways that matter—slew rate, noise figure, and gain-bandwidth product—and in our testing it sounded
the same.
Despite being an avid bass player in my high school years (before i grew a much stronger interest in playing guitar) I had never really geeked out on bass gear in the way I have with guitar, so tbh i’m completely out of the loop, i don’t really know much about bass gear other than typical hardcore/metal oriented applications involving sansamp bass drivers, ampeg gear if you’re lucky, musicman stringrays are awesome, and for DAW recording - running dual tones with clean sub / dirty parallel channels for good results (with line6 pod farm2 - yes i still use it
), and also glancing at all the different offerings/demos from Sushi Box gear, entering a whole other world of bass things i don’t really understand.so i guess that’s a lot of words to descibe how it’s quite satisfying to build and try something from a completely fresh perspective, ie. a modern bass driver.
In my completely uninformed opinion - I think this sounds heckin awesome with my Squier VM P-Bass (although running into an SLO100 clean channel and 4x12 guitar speakers)
- The 'mod' control is described as sweeping between 2 different distortion circuits - 'alpha' and 'omega' apparently. And it does sound like that - appears to sweep between vintage and modern inspired channels, and they sound distinct enough to warrant blending.
looking at the schematic it would mostly appear to be sweeping between x2 different EQ/filter pathways that look quite similar, with one having an additional fixed gyrator filter.
- 'blend', and 'drive' are fairly self explanatory.
- the 'level' control is not a master volume. it's peculiar in this case that it follows directly after the 'mod' control, and before the blend.
so really, the level control, being the 'distortion level' i guess, behaves as another blend control. despite how weird this is (to me at least), it actually works really well to foster a wider variety of tones/textures with the blending.
- the bass toggle ('growl' per darklgass), switches a 68n in parallel with a 22n coupling cap not far after the input buffer. good feature. i like it toggled on.
- the high mid toggle ('bite' / 2.8K per darkglass) appears to be a 'presence' boost in the EQ range as described. Still undecided on this, but it works well.
so despite having no master/output control (which doesn't seem to matter) it's a brilliant little package that makes your bass sound beastly with as much or as little drive/colouring as you want.
Demo:
