[2233] Boss SD1 More Mids

Date: July 7th, 2017 | Comments : [1] | Categories: DIY.

SD-1 tone control

This is the basic tone control section of the classic Boss SD-1 distortion pedal.

I got interested in the tone section when I was modeling it to compare to the TS-808 pedal, as mentioned in a previous post. I was thinking about an old mod that involved changing the capacitor in the low pass R-C section to open up the mids. It then occurred to me that the mids could be opened up by changing the value of R7 as well since it doesn’t alter the gain of the active part of the tone control. This lead to an idea to substitute a pot for R7 to allow adjustment of the mid-range.

SD-1 tone control

I have included a fixed resistor to limit the range of the filtering for a smoother response. This is easy to implement in the Boss pedal by removing R7 and substituting the new components into the pads as shown below.

SD-1 mids control

Adjusting the potentiometer will allow more mids to go through to the active tone control opamp section. This is similar to the low pass in the Rat pedals except the active tone section that follows makes it more versatile in the SD-1.

The same mid-range mod would work in a TS-type pedal but the component values would be different. The fixed resistor should be 100 ohms and the value of the pot as 1k ohms. In the TS, the 1k resistor coming from the output of the first opamp section is the one to change – the other end of the stock resistor is connected to the 0.22uF filter capacitor in the Tube Screamers.

It’s a simple mod, and the only trouble now is finding a good place in the box to mount the new mids control.


One Response to “Boss SD1 More Mids”

[778565] admin Says: 8:06 am, July 17th, 2017

For those who have bought the AMZ SoS pc board, I have just added instructions to its support page for this mod. Thanks!


AMZ Home Page

Guitar FX PCBs