A while ago I started building a treble booster, pretty much based on this circuit. I had actually completed the build when it turned out there was something wrong with the circuit (hence the name of the blog). The project was put away for some time, but then a few weeks ago I decided to give it a new try and not to give up until i had a working pedal. Boost the signal or die trying.
The circuit itself is pretty simple. Basically it’s just an (intentionally) badly designed amplifying stage. The signal gets amplified in a quite non-linear way as the cicruit will indeed boost the higher mids and treble, but it will also add quite a bit of overdrive. Here’s my version of the circuit:
R3 should actually be placed after the Rx resistor, this allows the bypassing of Rx to affect the biasing of the transistor, as R2, Rx and R3 form a voltage divider.
The parts used are: BC107B transistor, R1 = 1MΩ, R2 = 120kΩ, R3 = 39kΩ, R4 = 10kΩ trimpot, R5 = 2,2kΩ, R6 = 390 kΩ, R7 = 10kΩ potentiometer, R8 = 100Ω and R9 = 220Ω. C1 = 22 nF, C2 = 68 nF, C3 = 10 μF electrolytic and C4 = 100μF electrolytic. D1 = 1n4004 and D2 is a red led.
The Rx resistor is bypassed by a SPDT switch and the whole cicuit uses a 3PDT switch for bypass which means it’s true bypass.
I decided to use the BC107 transistor as it is a fairly good compromise between a sound some people might call “vintage” and features that makes it easy to use in a practical situation (i.e. NPN which makes it possible to use negative ground and thereby a shared power supply, and it’s silicon which makes it a lot more resistant to temperature changes, or at least that’s what the internet says, haven’t actually used germanium transistors).
I built the circuit on stripboard which is an easy way to get a lot of parts fitted on a small surface without having to mess around with any etching chemicals. Here’s the stripboard layout:
After some trial-and-error I finally got it put together, here’e what it looks like now, inside and outside:
I decided to give it a rather fancy look, by using a aluminum knob for the voulme control and sanding the surface with a quite rough sanding paper. The design was inspired by my old hi-fi reciever, I found this suitable as the treble booster might the most lo-fi circuit ever used for guitar processing.
I will post a video demo soon, I just have to find a place where I can play it loud enough to make the booster justice. Can’t really do that in my appartment.
What's wrong with this circuit? 