VOLUME: It does the thing.
MIDS: This control was added because the stock TSF circuit contains a fair bit of mids, and a touch more is added after this control with the fixed gain stage. The stock values of this circuit give you a scoop of 6dB at 450Hz, near the “body” frequency of electric guitar. Turn this knob all the way down for a deep scoop, which balances the pedal better against British-style amps that have intrinsic mid boosts, or keep it up to push back against naturally mid-scooped amps, such as Fenders. Or, just use it as a regular mids control and have fun with it!
DRIVE: This controls the amount of gain in the first stage, feeding it into the mids scoop circuit and a second stage with a fixed gain level. Turning this control to the minimum delivers an excellent sparkling-clean boost and turning it to the maximum gives you a meaty distortion sound. It’s important to note that the Knight School Overdrive is incredibly touch sensitive, so this knob should be set accordingly. You can set it to open up with your hardest strumming for dramatic effect or keep it relatively high and only use it on the quiet parts.
The Knight School Overdrive accepts a center-negative DC power supply capable of supplying 9 volts and at least .5mA of current (over is fine). Plugging in anything other than this (center-positive, AC, higher voltage) will damage the pedal, maybe even beyond repair. Check your supply and make sure it says all the right stuff. Plugging in the wrong supply will void the warranty and possibly summon a puff of ozone-tinged smoke. Trust me, you’d hate it.
DIY KIT INFORMATION
The circuit board has everything labeled as to what part goes where. You'll find the below image very helpful to identify what parts are what. There's also a video below showing you how the process will go.
WATCH IT BEING BUILT
A BIT ABOUT PARTS
Identifying the resistors
Here is a list of mods that you can try if you're feeling it! We only provide you with the components for our build, but feel free to try these mods with other parts you obtain and we are happy to chat with you about how it's going!
Adjusting the gain range:
Several parts in this build affect the overall gain but the easiest one to switch out and “get right”is the 68K resistor. The entirety of the first stage amounts to a bandpass filter, and we don’t need to get into what that means, but just know that filters can have gain, and the way that the gain on this filter is calculated is the total resistance of 82K + the 1M potentiometer over thevalue of the 68K resistor. Therefore, as you decrease the 68K resistor, the amount of gain goes up (and increasing makes the gain go down). Try playing with this value to get more or less gain out of the circuit.
Additionally, the 82K resistor plays a role in available gain by setting the minimum and maximum gain of this filter. When the Gain knob is set fully counter-clockwise, the resistance inthe circuit is 82K ohm. At maximum, it is 1,082,000 ohms, or 1.082M ohm. As you increase the 82K resistor, the minimum gain goes up when the Gain knob is set to minimum, but the maximum gain (with the Gain knob fully up) also increases. If you decrease this value, you will notice the minimum gain go down, but as that resistor value decreases, the maximum resistance becomes more and more trivial. If you lower that resistor to, say, 22K, the minimum value is now 22K, but the maximum value is 1.022M, a trivial addition to the overall gain.
Example: If you’d like the gain level to be, at minimum, as great as the stock circuit when the knob is maxed, replace 82K with 1M. Turning the gain control up will now yield a total resistance of 2M, which equals a ton of gain. Extreme gain values may cause this circuit to be unstable and noisy, however.
This circuit is called a “twin-T notch filter” which cuts a “notch” out of the frequency band, in this case the mids band. Changing either of the two capacitors (560pF and 10nF) affects the depth of the notch, while changing out the 150K resistors changes the frequency. Without dropping the math on you, reduce both resistors to increase the frequency at which the scoop occurs, and increase either 560pF or 10nF to offer a deeper scoop. The values of this circuit are borrowed directly from the Matchless Chieftain amplifier, and amount to a 6dB cut at ~450Hz when the control is turned fully counter-clockwise.
Changing both resistors: 150K → 82K = 820Hz, 6dB cut
150K → 220K = 300Hz, 6dB cut
Changing the 10nF capacitor: 10nF → 22nF = ~450Hz, 12dB cut
10nF → 4.7nF = ~450Hz, 2.6dB cut
The mids circuit is passive, meaning unpowered, which also means that a little volume is lost. The 2M2 resistor on the right side of the IC determines the amount of gain needed to “make up” for the loss from the mids circuit, otherwise known as “makeup gain.” You can lower or raise this amount, by proportionally lowering or raising the value of this resistor.