treble booster mods ?

[fuzzo]

Hi every one,

two months ago  I did a treble booster (a EHX screamming bird) with a standart NPN transo. the schematic:



the pedal contains a BC109C.

But the sound is very agressive and shrill. It hurts my hears (espcially with the 7n input cap)


You see some mods to have a smoother sound ? tone pot like the keeley java boost ? add cap somewhere ?  change some values ? 

Or I must find a NPN Ge transo ?

[Dragonfly]

Change the caps marked with a red dot to the values shown  - you should like it a lot better..still not a germanium boost, but lots more bass.... basically a treble-ish boost / LPB1

there are other things you can do, but this should satisfy....

[asfastasdark]

If the change from 7nf input cap to 47nf cap is what you're looking for, I think you should just change the input cap to a higher value. It will give your sound less treble, but maybe that's exactly what you're looking for. I wouldn't change the 47k's value because it would screw up the entire transistor base bias. Or it might help to change the output cap to a different value. I don't think a different transistor is going to do much.

EDIT: Beaten to it  .

[fuzzo]

thx for your answers,

I'll check in my stock if I've the 100n to try the Dragonfly's mod.

there are other things you can do

You can say more ?

[sean k]

Theres also the option of a pico farad cap to ground at some stage to take the extreme shrillness off the very top.

[Dragonfly]

there are other things you can do

You can say more ?

Sure - but I'll hold off typing them until you see how you like the first set of changes. 

[Caferacernoc]

Theres also the option of a pico farad cap to ground at some stage to take the extreme shrillness off the very top.

Simple way to implement: Put a .001uf cap across the outside terminals of your volume pot. Adjust size to taste.

[fuzzo]

Theres also the option of a pico farad cap to ground at some stage to take the extreme shrillness off the very top.

You talk about some oscillation caused by the extrem high frequencies ? Or something else ?

I'm trying the dragonfly's mod.

[mnordbye]

Try putting a small ceramic cap from the transistor base to the collector (the left and top connectors of the transistor). I suggest trying a 100pF value ceramic first.

Magnus Nordbye

[fuzzo]

Hi

I've tried in puting 100n before the pot volume and another one like input cap and the sound is better !! more smooth less strident, even with the 10nf input cap. But like this it's a LPB1 ehx boost, I remember i did on last year (but I explosed the box with a hammer )

I'll try it with my valveking.

thx.

[Gus]

That circuit is one you should be able to find in textbooks.  Try to find a transistor text book, that four resistor bias and gain setting circuit is often covered.

For guitar use think about
Input resistance
The high pass filter caused by the input cap and input resistance.
The bias and gain math used for selecting the resistors
The output cap size withe the volume control and what ever it is connected to adjust the output RC

You will learn things like that the input resistance has to be lower than 47K just looking at the circuit.  Input loading can sometime change the sound of the pickups.

That is a good circuit to learn from if you want to build effects.

[fuzzo]

What do you think if I put a pot like the blend pot in this document instread of the switch ? more tone options or not ? 'cause with the switch I've just two positions , so maybe I can increase the possibilities with this kind of control.