Treble booster

After creating the AC5, a treble booster should be the next project, to recreate the famous Brain May sound!

The result is a kind of “uber” booster, making it possible to use different configurations (a valve tube, a germanium transistor and a silicon transistor). It also contains switches to tweak input condensators (changing the RC filter). The booster will also have a bias resistor trim pot.

I found out that Greg Fryer made a sketch of a Grand Poohbah Treble Booster, which has the same idea: having multiple treble boosters in one package.

Usage

Three footswitches can be used to select a particular booster. The sign path is from the right (input) to the left (output), passing the three different boosters. The LED above the footswitch indicated if the particular booster is activated, or bypassed.

The output volume of each booster can be controlled by the dial above the footswitch (the one for the Ge booster is placed somewhat to the right, to make room for the tube).

Three switches can be used to tweak the sound:

• The leftmost switch toggles between an input capacitor of 5nF or 10nF for (only) the Si booster;
• The middle switch (de)activates some extra kick for the Tube booster;
• The rightmost switch toggles between the setting the Tube booster to and actual Treble booster or an Overdrive pedal.

The switches at the side of the booster can be used to turn of the Tube and Germanium boosters:

• The Tube switch turns of the tube circuit (both the heater and the circuit itself, so no power will be lost to the heater);
• The other switch turns of the power to the transistor circuits (both Germanium and Silicon).

Currently, if both switches are in the on, the booster will unfortunately produce a high pitch noise. This noise is not present when only one of the switches is on. When both switches are off, no power will go to the circuits.