GUILD / CORNISH: Silicon treble booster

As I was recently playing around with the Colorsound booster made by Steve Williams of Pig Dog fame, I noticed some similarity to the Guild Treble Booster, AKA the Brian May Box.

I made a slightly simplified version of the Guild, without the buffer based on one of the Fryer Boosters.  I kind of free-styled the build, working without a layout using a spare piece of vero. 

This is going into a Hammond 1590B enclosure, which is normally too small for anything that I make.  This will just have an on/off switch and no knobs.

I used a vintage glob top NPN silicon transistor pulled from an old PA head preamp.  While I listed a BC107 on the vero layout, almost any silicon NPN transistor will work - all the common ones certainly do.  

SILICON TREBLE BOOSTER - VERO LAYOUT

I tweaked a few values and moved some parts around on the board after the photo was taken - will update with some new photos while boxing this up.

The links are placed under the board, primarily for looks - and same for the standing resistors. 

C1.  This controls the bass cut on the input.  i.e. it shapes the treble boost.   

C5 rolls off high frequencies at the output, which may seem a little counterintuitive for a treble booster, but I quite like it.   

C2:  A smaller cap can be used for C2, with no real change - 100pf would be fine as an example.  

C3 - 22uf will also do the job.  

And just to confirm that it's a booster...  440hz sine wave used with a 6n8 input cap, 3n3 output cap

R5 and R6 control gain - the circuit started with 6k8 and 2k4 in these positions.  I moved to 10k and 2k2 as they're more common values, and it gave a bit more output.

Just as a side note:  the Guild treble booster also appears as the boost in the Vox Brian May AC30.  Albeit with a high/low boost switch, which just adds 10k series resistance to ground on the 47u bypass cap.