Switching between multiple resistors

[Grubb]

I'm playing around with the Six String Stinger circuit at the moment, planning out a few potential mods. Having learned this week that this OD/boost pedal has absolutely nothing to do with a very clean high headroom boutique tube amplifier - which is obvious on reflection - and is instead built on the platform of Jack Orman's Minibooster, I am thinking through what I can tinker with to get different sounds out of the circuit. One of the ideas I'm considering is to increase the level of overdrive by decreasing the value of the source resistors on each miniboost stage (there are two in the pedal). Orman's original design had the value at 100R, with 1K as a suggested value for mild overdrive. Meanwhile the stock value on the Vertex unit (which is a slightly gritty boost) is 10K.

I intend to trial a few values and put my preferred settings on a switch. It seems easy to swap between two resistor values on each source resistor using a DPDT switch. Is it possible to switch between 3? I had in mind the King of Tone switching that can easily be set up to toggle between Boost, OD and distortion, but that's opening and closing diode clipping circuits rather than toggling between component values. I can't at this moment apprehend how to do it in the context of the Stinger:


I've just used SPDT switches in this mockup, as I try and work out how to do it. I haven't attempted to connect the switch on the right side of the diagram yet, just to preempt any smart Alecs Please feel free to point out any areas of misunderstanding you can identify. Can I hook up all 3 resistors?

 

[BuddytheReow]

You can use a spdt on/off/on, but you’ll have to tweak the resistor values since on both ends of the switch you’ll have 2 parallel resistors. The alternative is a rotary switch which will solve everything.

 

[Grubb]

Thanks @BuddytheReow. I could be getting this all wrong, but using a parallel resistance calculator, I got things pretty close like this:

102R in parallel with 10K is 100R (tbh 100R in parallel with 10K is probably close enough)
1K2 in parallel with 10K is 1.1K
Off position is 10K

Does that sound about right?

 

[vigilante398]

Thanks @BuddytheReow. I could be getting this all wrong, but using a parallel resistance calculator, I got things pretty close like this:
View attachment 25558
102R in parallel with 10K is 100R (tbh 100R in parallel with 10K is probably close enough)
1K2 in parallel with 10K is 1.1K
Off position is 10K

Does that sound about right?

Yup, nailed it. Looks good to me.

 

[Feral Feline]

Great idea for a Mod, Grubb.

I previously came across the following at Rob Robinette's site:

It inspired me to make a few mods on some builds, but I haven't used the idea in ages.
Since I'm too lazy to do the math I use one of the many online parallel-resistor calculators to sort out my needs, this one is my favourite calc (super simple):

PARALLEL RESISTOR CALCULATOR

I'm going to copy your idea to my own Orman Booster build and call it the "Grubb" Switch.
Thanks for that!

 

[MichaelW]

I'm playing around with the Six String Stinger circuit at the moment, planning out a few potential mods. Having learned this week that this OD/boost pedal has absolutely nothing to do with a very clean high headroom boutique tube amplifier - which is obvious on reflection - and is instead built on the platform of Jack Orman's Minibooster, I am thinking through what I can tinker with to get different sounds out of the circuit. One of the ideas I'm considering is to increase the level of overdrive by decreasing the value of the source resistors on each miniboost stage (there are two in the pedal). Orman's original design had the value at 100R, with 1K as a suggested value for mild overdrive. Meanwhile the stock value on the Vertex unit (which is a slightly gritty boost) is 10K.

I intend to trial a few values and put my preferred settings on a switch. It seems easy to swap between two resistor values on each source resistor using a DPDT switch. Is it possible to switch between 3? I had in mind the King of Tone switching that can easily be set up to toggle between Boost, OD and distortion, but that's opening and closing diode clipping circuits rather than toggling between component values. I can't at this moment apprehend how to do it in the context of the Stinger:

View attachment 25557
I've just used SPDT switches in this mockup, as I try and work out how to do it. I haven't attempted to connect the switch on the right side of the diagram yet, just to preempt any smart Alecs Please feel free to point out any areas of misunderstanding you can identify. Can I hook up all 3 resistors?

Would love to hear how this turns out. I'm intrigued by this pedal.

 

[Grubb]

Would love to hear how this turns out. I'm intrigued by this pedal.

I like it stock, but there's always the possibility for more. The gain range is one ripe area for mods.

The other is the tonestack. The SS Stinger has a BMP tonestack which is tuned for fattening up single coil guitars and emphasises some bass and low mids to do this, with a slight, narrow mid scoop above that range. It doesn't sound good for a darker guitar or amp. A few users on this forum have described a muffling effect from this pedal which is almost certainly a result of the tonestack tuning not complementing their other gear.

I have two competing ideas for addressing this and making the pedal more versatile. My first idea is to tune the BMP tonestack for a flat response at 12 o'clock, with bass cut and treble cut available on either side of the pot's travel. Then I would offer an alternative value resistor on a switch for the LPF side of the BMP stack, to introduce a TS style mid hump.

The other, more flexible option would be to scrap the BMP and put a James tonestack in its place, but I haven't figured out whether the insertion loss of about 20dB will mean a gain recovery stage is needed. I'm assuming so.

Great idea for a Mod, Grubb.

I'm going to copy your idea to my own Orman Booster build and call it the "Grubb" Switch.
Thanks for that!

Let me know how you get on with that. I'm intrigued to hear how it sounds. I've only just come across Rob Robinette in the past fortnight - it's good stuff!

 

[mdc]

You can wire a dpdt as a sp3t: https://forum.digikey.com/t/wiring-a-dpdt-switch-to-act-like-a-sp3t/924

You need an on-on-on and you might have to flip the jumper around depending on if you have a type 1 or type 2 switch.

 

[Grubb]

Thanks for that link @mdc. I have saved the graphic from there to my reference folder, I'm sure I will need that again.

 

[mdc]

No problem! If you have a Type B, this is what you'll want to do to switch between 3 resistors w a toggle. Flip the jumper so it goes from middle left to bottom right for a Type A.

 

[MichaelW]

No problem! If you have a Type B, this is what you'll want to do to switch between 3 resistors w a toggle. Flip the jumper so it goes from middle left to bottom right for a Type A.

This is pretty cool, no reason it wouldn't work as a diode option clipper.....hmmmm...now you're giving me some new ideas......