Adding Bias Mod To Marigold (Yellow Hybrid Tone Bender)

[mdc]

If you're using a power supply brick, all you'd need to do is sacrifice one of the barrel cables—splice the power side and solder on a pair of aligator clips. Clamp those to whatever pots you have lying about until you find a value that works for a given circuit. The sag control in the Fairfield Barbershop is just a 10K variable resistor/pot in series with the 9V supply.

 

[debrad]

Quick follow up...built this to adjust the input voltage on my Marigold build (and any other 9V centre negative pedal I want to play with) based on a couple of suggestions on Beavis Audio (and Zachary Vex's suggestion to use a 5k potentiometer).



Hooked it up to my Marigold and was able to drop the input virtually all the way down to it's lowest setting and the only thing that changed was the overall volume and the brightness of the LED.

 

[mdc]

Ahh heck, it was worth a shot for sure... but as @Chuck D. Bones said, it's not a design that's particularly friendly to bias tweaks.

 

[zgrav]

on the bright side, you can use that box to see if other pedals might be better choices for adding a "dying battery" pot.

 

[debrad]

You're right @zgrav, the "dying battery box" was dead simple and bound to come in handy - I'll definitely be trying this little box on just about everything now!

 

[andare]

Quick follow up...built this to adjust the input voltage on my Marigold build (and any other 9V centre negative pedal I want to play with) based on a couple of suggestions on Beavis Audio (and Zachary Vex's suggestion to use a 5k potentiometer).

View attachment 25181 View attachment 25182

Hooked it up to my Marigold and was able to drop the input virtually all the way down to it's lowest setting and the only thing that changed was the overall volume and the brightness of the LED.

I understand how this works except for the resistor.

 

[mdc]

The pot is being used as a voltage divider, so that resistor to ground keeps the voltage from going all the way down to zero.

 

[Bricksnbeatles]

Take a look at how the voltage starve works on a Buzzaround. I recommend that method. Only starves q3

 

[andare]

The pot is being used as a voltage divider, so that resistor to ground keeps the voltage from going all the way down to zero.

Aha, same way you use a resistor on the collector of a transistor in a fuzz face when you use an external bias pot. Makes sense. Which value would I use, 1k?

 

[debrad]

Which value would I use, 1k?

The Beavis site recommended a B10k potentiometer with a 2.2k resistor but I followed Zachary Vex's recommendation for a B5k pot and substituted a 1.2k resistor since my pot choice had a lower overall resistance.

 

[andare]

The Beavis site recommended a B10k potentiometer with a 2.2k resistor but I followed Zachary Vex's recommendation for a B5k pot and substituted a 1.2k resistor since my pot choice had a lower overall resistance.

Thank you!
Obviously my Sag Pedal will use one of those giant 45mm knobs in a 1590LB enclosure.