TS + Baxandall

[Mixa]

Can I just insert a Baxandall (Treble and Bass) circuit in my Tube Screamer instead of the stock tone control? Or do I absolutely need another opamp?

EDIT: Same question for Klon clone..?

[idy]

You can "just" sub a baxandall but: both circuits have second stages that are non-inverting and baxandall uses opamp in inverting configuration. So awkward to to do as a "mod" on an existing board.

Probably no big deal to have a circuit that inverts overall but circuits that use baxandall often use inverting first stage also, like Xotic AC/RC booster.

[Mixa]

You can "just" sub a baxandall but: both circuits have second stages that are non-inverting and baxandall uses opamp in inverting configuration. So awkward to to do as a "mod" on an existing board.

Probably no big deal to have a circuit that inverts overall but circuits that use baxandall often use inverting first stage also, like Xotic AC/RC booster.

Thank you, I learned something new there! :-) So, it should be easier to do it on the Klon, because the stock tone circuit is based on the inverting opamp (as well as the preceding first stage of the same opamp which is also in inverting configuration). That is, IF I'm getting it right...

The eq on the Sick As works PERFECTLY, but it does have an additional opamp...

[marcelomd]

That tonestack in the Klone is a treble only Baxandal, right? It's a "simple" mod to add the bass part.

This is the original:

Remove the 100k resistors (R22 and R24) and add the corresponding components for the bass part (R4, R5, C2, VR2):



This is a hack, I have no idea how the Sick As is implemented.

[marcelomd]

Can I just insert a Baxandall (Treble and Bass) circuit in my Tube Screamer instead of the stock tone control? Or do I absolutely need another opamp?

EDIT: Same question for Klon clone..?

TS Baxandall is pretty much the Xotic BB Preamp. For modding an existing pedal, I'd make a dautherboard with the extra opamp and tonestack. If building from scratch, just follow the BB preamp schematic.

[Mixa]

That tonestack in the Klone is a treble only Baxandal, right? It's a "simple" mod to add the bass part.

This is the original:

Remove the 100k resistors (R22 and R24) and add the corresponding components for the bass part (R4, R5, C2, VR2):



This is a hack, I have no idea how the Sick As is implemented.

Thanks Marcelomd!
I planned to implement the Xotic baxandall, but your schematic looks good.

One more beginner question... the non-inverted input of the opamp goes to ground, is it ok to go to Vb instead?

[marcelomd]

That tonestack in the Klone is a treble only Baxandal, right? It's a "simple" mod to add the bass part.

This is the original:

Remove the 100k resistors (R22 and R24) and add the corresponding components for the bass part (R4, R5, C2, VR2):



This is a hack, I have no idea how the Sick As is implemented.

Thanks Marcelomd!
I planned to implement the Xotic baxandall, but your schematic looks good.

One more beginner question... the non-inverted input of the opamp goes to ground, is it ok to go to Vb instead?

Sure, connect to VB. My intention was just to illustrate how to convert from treble-only to treble+bass.

The schematic is from ESP (https://sound-au.com/). One of the best resources for audio electronics. Check it out. He usually uses symmetric supplies, so remember to account for that if you use any of his schematics.

The Xotic BB Preamp is a great sounding pedal. And it has one interesting thing. It's a complete TS _plus_ Baxandall. The original tonestack is still there, just fixed. If you want to play a bit with the design, maybe you can use that opamp stage to make a mid control or something.

[antonis]

[Mixa]

Did it on a Klon clone, works like a charm
The only difference is, I didn't have the 50k pots, tried 25k, which turned out to be plenty for Bass, but not sufficient for Treble, so I used a 100k there.
To whom it may concern  I also put a jumper instead of the 2k resistor to increase the range of the gain pot. I also plan to install a diode switch between the stock diodes (1N34/D9E) and 1N4148, which will likely make it the ultimate low/medium gain overdrive 

Thank you everyone, this is such a great place!

[Mixa]

On the Klon, the values are 820p and 392k... Being a beginner, I'm not even shure what these do 

[antonis]

The above is a Xotic BB Preamp with omitted TS Tone circuit..

IC2A inverts the signal so output is in phase with input 'cause IC2B also inverts the signal..
R16 & R15 set IC2B stage gain (R16/R15) and C9 & R16 form a Low pass filter (0.159/C9*R16 corner frequency)
(of course, C9 can be of much higher value but I just mode its value so to maintain original design corner frequency..)

[fryingpan]

Keep in mind that much of the character of a TS is in its tone section (and high-passed clipping, of course). If you mod the TS removing its tone control it's basically a generic-sounding overdrive. I'd suggest just adding a bass control to the second op-amp, like on the Digitech Bad Monkey IIRC.

[Mixa]

I noticed the sound suddenly gets much brighter when the gain knob is turned past 9 (from 0 to 10)... Any ideas..?

[antonis]

On which particular circuit you refer on..??

[Mixa]

The Klon clone I have mentioned here. I did jumper R10 and reduce the value of R11 to get more gain. I adjusted the capacitor in parralel with R11 to keep the same cutoff freq

[antonis]

Are we talking about this Klone clone ..??

[Mixa]

Yes sir, that's the one
R11 is now 3.3K, and C7 is 390n
R10 is gone (jumpered)

[antonis]

By setting Gain A pot near max you raise the HPF corner frequency (the complex one formed by R11//C7, R10 (short in your case), pot lug3-wiper and +4.5V filter cap,,) hence you result into brighter sound..
(more bass rejected..)

[Mixa]

Thanks, I love how much I learn from you guys!
I know a lot of drives/distortions exibit this kind of behavior, it just seemed strange how suddenly it becomes a lot brighter (changes instantly when it is turned past 9), not gradually as expected

[Mixa]

How 'bout a three band baxandall? Anyone has a schematic that is adequate for a guitar pedal? Maybe based on Wampler deluxe series (Tumnus Deluxe, Clarksdale...)