Vox treble booster input impedance

[Silvio55]

Hi, I want to build this circuit, and wanted to know a little bit before building it; I love how the Rangemaster and the Fuzz Face roll of treble when you put your guitar volume at 10, but have that treble back as soon as you roll down the volume, and how the clean up perfectly. With Ge, I find that treble roll of a bit excessive, and I tried a Si FF and it was just perfect, exactly the sound I was looking for.
I'm having trouble with the FF so I wanted to try a silicon booster type circuit, like the Rangemaster, but with a big cap at the input and use it like a sort of a fuzzy overdrive, just like I use my RM but with a little less treble loss at full volume (and less hiss overall) and clean up by just rolling the guitar volume down.
I understand that low input impedance is the cause of this behavior on both circuits and wanted to know if this circuit behaves in the same way.

Or if anybody just built a silicon RM and have some tips to share, that would be great!
Thanks!

[antonis]

Paricular circuit impedance roughly is 5k..

As it is, input HPF corner frequency is about 1.5kHz but this only stands for zero impedance guitar output..
For a 10k guitar output impedance (guitar volume full up), corner frequency is about 480Hz, hence for intermediate Vol pot settings corner frequency lies between 480Hz and 1.5kHz
[ formula is f = 1/2π*22nF*(5k + guitar out) ]

Second pole HPF is made up of 10μF cap and intrinsic Emitter resistance (26/Collector current), which is about 600Hz..
Third pole HPF is made up of 47μF and 2k2+500k, which is subsonic..

As you can realize, input HPF and guitar output impedance toghether with Emitter resistor bypass cap are co-stars in treble handling..

P.S.
With all reservations for my by heart calculations..

[kaycee]

You can slot a silicon transistor straight into a RM circuit and it will work. Any low gain silicon is worth a try, I'll say BD139 before Ian does. The Vox is ok (with a larger input cap), but the RM is better. You could also go for one of the many Brian May treble boosters knocking around.

[iainpunk]

You can slot a silicon transistor straight into a RM circuit and it will work. Any low gain silicon is worth a try, I'll say BD139 before Ian does. The Vox is ok (with a larger input cap), but the RM is better. You could also go for one of the many Brian May treble boosters knocking around.

ow, you got me there. i do love that little transistor! if you want to keep with the PNP craze, you can use the BD140
i really recommend playing around with the bias of the range master as well, that both affects the impedance, gain and tone of the circuit.
the bias is affected by all 4 of the resistors surrounding the transistor, but i recommend starting with the collector resistor, since the other popular option, changing the 68k, changes the input filter cutoff as well.
my mod also eliminates crackle when turning the pot.

cheers, Iain
EDIT: does postimg.cc work on your end or is the site down again?

[Gus]

look at the sims for some ideas
https://www.diystompboxes.com/smfforum/index.php?topic=107047.msg970682#msg970682