Treble Booster has too much treble

[fuzz guy]

Some of you might have seen my other thread about my first pedal build, a Rangemaster kit. I like the booster, but it's just got too much high end.

Is it possible to tweak the values of a component or two to lower the treble a bit? I've posted the schematic which comes from the PDF build document found on the Fuzz Dog site.




Here's the BOM,

R1 1M
R2 3K9
R3 470K
R4 1M
BIAS 100K preset
C1 4n7
C2 47u
C3 47u
C4 10n
Q1 Russian 1T3086
BOOST 10KA
D1 1N4001

[theehman]

Change C1 to a higher value.  Try a. 0068 or a .01.

[Kipper4]

Try changing C1 bigger

[ashcat_lt]

Changing C1 gives more bass, not less treble. 

[bool]

You can try one of the following:

- add a small cap across the transistor B-E (470pF could be a starting point)
- add a small cap across the transistor C-B (220pf could be a starting point)
- add a small cap across the "boost" pot (contact 1-3, 4700pF could be a starting point)
- alternatively, same as directly above, but across the transistor C-E

[fuzz guy]

Change C1 to a higher value.  Try a. 0068 or a .01.

Changing C1 gives more bass, not less treble. 

I may try this first, even if changing C1 will only result in more bass I'm hoping the overall effect will balance out the tone a bit more.

If that doesn't do it I'll get into those last suggestions. Thanks.

[mac]

You can try one of the following:

- add a small cap across the transistor B-E (470pF could be a starting point)
- add a small cap across the transistor C-B (220pf could be a starting point)
- add a small cap across the "boost" pot (contact 1-3, 4700pF could be a starting point)
- alternatively, same as directly above, but across the transistor C-E

or a small cap across the 1M resistor at the output.

mac

[amptramp]

A larger value for C1 may help reduce thermal noise as well.  The parallel resistance of Rbias and R3 sets the resistive noise at frequencies below the cutoff imposed by C1.  If C1 is increased, the frequency range where Rbias and R3 are in parallel with R1 and the output resistance of the guitar for noise purposes drops down and reduces the noise.  Even if the guitar is set to a midpoint volume setting where the resistance is highest, it is still on the order of the other resistors.  This would increase the midband and allow you to turn down the boost control which would give you the effect of less treble.

[fuzz guy]

I swapped a 6.8nF into C1 today and it's much better. Still has a treble bite and the character of the pedal has remained, just tempered the high end harshness a bit.

I'll play it like this for a bit, will probably try a 10nF eventually though just to see what it's like before I settle on a final value.

Thanks for all the help.

[fuzz guy]

Yep, the 10nF is the one.

Played for a couple weeks with the 6n8 and it was still too much treble. Today I swapped it out for the 10nF and it's exactly what I've been looking for, just the right amount of vintage grit and amazing tones all the way through it's boost range.

Playing my P90 equipped Tokai Love Rock Special into my little Laney Cub12R with the Rangemaster dimed, perfect Iommi sound.

[pinkjimiphoton]

Changing C1 gives more bass, not less treble. 

bingo

a small cap to ground would work too, maybe 100-470p before the output cap. maybe smaller even... 22-47p

i like a 10n on a rangemaster, too. nice edge and decent mids

[mac]

Mine has a switch to choose 6n8 and 10n.

Playing my P90 equipped Tokai Love Rock Special into my little Laney Cub12R with the Rangemaster dimed, perfect Iommi sound.

My LC30 II is very happy with it.
It also makes my Valve Jr and Deacy sCream.

mac

[Gus]

R3 would be a resistor to adjust if you want a simple bias adjustment at the input voltage divider. R3(fixed resistor with an adjustable resistor) adjustment changes the input resistance less than the lower value base to ground resistor. The input resistance will be less than the base to ground resistance value.

The emitter resistor being bypassed allows it to be changed as well.

Your input cap value will need to be adjusted for the input resistance the circuit has.

Adjusting a treble booster has been covered over the years.

Have you looked at the GEOFEX article?

[mac]

This is the freq response of a silicon booster, but it's similar to a RM.
A bigger input cap gives more bass and less Q.



mac