Squeezing some contour 'presets' into this onboard pre

[Eddododo]

edit: cleaned a few things up and made it more coherent.

I'm working out an onboard preamp for a bass build I'm starting, and I'm trying to figure out an elegant way to add two switchable 'preset' contours.

The wiring scheme will be like this-
-Switchable active/ passive
-Passive tone control in both modes
- VVT + Bass/Mid/Treble + 2 'contours'

The contours would be switchable, with fixed values (maybe with trimpot adjustment to tune), a lot like the various 'contour' buttons on a lot of amps.


1) One is a classic slap-friendly scoop
2) The other is a Low-mid bump, with the highs sloping off into the distance. A fat but focused root-forward tone without string noise.

So looking at my scheme- I'm trying to figure out a good way to switch these in with some elegance without adding a thousand unneeded components.. its already pretty big, and though I can make the room, there's also the current draw of each op-amp to consider.

A couple things I've been mulling around:
-Some application of gyrators. I'm mostly familiar with these in the differential(?) eq circuits, panned between inverting and non-inverting inputs.. I'm not sure how I'd make use of it here, especially since I'd likely need it to be further shaped.

-Simply adding a couple extra 'bands' of that same tone stack (what do you call those mids paired with a baxandall?). I just don't love the dependence on interaction with the stack.. I feel like it should be a distinct global change to the sound.. maybe it's worth testing just to see if it somehow sounds more 'musical' being interactive.

-Just adding a couple caps tied onto some input caps and feedback caps.. this could maybe take care of the 'mid bump' setting, especially since this probably works better as a bandpass, rather than falling off of a peaked frequency.. though a peak frequency center IS the sound I'm imitating and exaggerating, so hmm..

- Or do I just add a section.. using an op amp stage would definitely let me dial in the sound I want without going crosseyed finding a sneaky way that also sounds good and is tunable.  I could have it switch in between the input/blend stage.. just seems a little clumsy.

-HMMMM I did used to like a parallel processing approach- just mix in a fully effected sound with the dry sound, which gives you this weird '.5 the effect' effect, but also leaves things extra natural sounding.. hmm.





I realize it may seem wasteful to have the dual op-amp input, and I may agree.. but I definitely want the active blending with persistent passive tone control (in addition to the active treble).  They could perhaps be FETS, and the dual op set goes to service with the tone presets... still seems a little clunky, but maybe the IDEA is clunky. Once I get to breadboarding and testing a few things audibly I'll see if I really feel that the active blend is worth the hassle and components.. If it's just cork sniffy and doesn't actually help well, then I can certainly free an op amp stage or two.


If you're wondering about the weird switching and extra resistors / tone pot at the input: the passive mode is obviously VVT, but when you switch to active the pickups are now isolated for active blending, so in order to retain the passive tone knob, I am using a dual-gang pot for the tone, such that there is a tone pot switched-in to the 'upper' pickup in active mode.  The extra resistors are to keep the pickups loaded the same, since they lose the other pickup's volume's loading.

[PRR]

You have drawn it as for a split supply, like +/-9V. How to do that in "onboard"?

> maybe it's worth testing just to see

+1

[Eddododo]

You have drawn it as for a split supply, like +/-9V. How to do that in "onboard"?

> maybe it's worth testing just to see

+1

I was just being lazy while drafting and forgot to edit it. I DID briefly consider doing a split supply, and it's not uncommon for basses to run off 18v, but as of now it's just 'shorthand' on the schematic.