Author Topic: Fet Master and Mos Master treble boosters  (Read 1869 times)

mac

Fet Master and Mos Master treble boosters
« on: December 21, 2015, 07:53:25 PM »
A Christmas present :)

A fet and a mosfet treble boosters.
Both try to mimic a Rangemaster.

To get a bell-like freq distribution with a peak at 1k5 Hz or so, I reduced the input impedance drastically to 10k. This is done with resistor Rz anc capacitor Cz in both schematics.
You can have the same effect by ignoring RZ and Cz and using a 10k at the gate of the fet, and something similar at the mosfet's gate but current draw will be higher.

Adjust Rbias to set drain at 7v or so.
No need for an external supply, a battery will last a long time.

Fet Master Schematic


Mos Master Schematic


Some LTSpice charts, ac and transient,

Fet Master vs. RM ac


Fet Master vs. RM transient



Mos Master vs. RM ac


Mos Master vs. RM transient


I used a 2SK117 Toshiba fet because of its high gain. Other well known fets do not have enough power, ie, enough output volume.

I tried different mosfets, the ones I liked are BS250 or BS170, and MTP3055 Motorola power device (at 200ua it needs some heavy heat sink :) )
I didn't like some IRFs.

The mosfet version has a bit more character and power, I guess it's because they have more gain.

Enjoy,

mac
mac@mac-pc:~$ sudo apt-get install ECC83 EL84

Kipper4

Re: Fet Master and Mos Master treble boosters
« Reply #1 on: December 22, 2015, 11:27:35 AM »
Neat Mac. A merry Christmas to you sir.
Only 11 components too looks like I'll have to bread it over the holidays.
Have a good one
"Duck_Arse
otherwise, you might end-up with SOIC or gullwings, for surface mounts."


Smoke me a Kipper. I'll be back for breakfast.

Grey Paper.
http://www.aronnelson.com/DIYFiles/up/

mac

Re: Fet Master and Mos Master treble boosters
« Reply #2 on: December 23, 2015, 09:04:40 AM »
Merry Christmas Rich

BTW, I set the drain at 7v to have a bit of dirt if the device is hot enough.
You can use a lower gain fet and set the drain at 4.5v to have a clean treble booster.

A couple of mods,
- change Rz to 10k + 50k log pot. At 60k the peak is flattened, and volume goes up.
- try different values of Cz, starting from 10n. It has an effect on the lows.

mac
mac@mac-pc:~$ sudo apt-get install ECC83 EL84

Gus

Re: Fet Master and Mos Master treble boosters
« Reply #3 on: December 23, 2015, 04:09:45 PM »
Like the schematics
Have you tried inductors at the input?

mac

Re: Fet Master and Mos Master treble boosters
« Reply #4 on: January 15, 2016, 09:17:30 PM »
Quote
Have you tried inductors at the input?

Gus,
The circuit uses the guitar coil as a part of the bandpass filter.
So there should be nothing between the circuit and the guitar.

If a pedal is placed in the middle, the peak is gone.
An input inductor might be needed.

mac

mac@mac-pc:~$ sudo apt-get install ECC83 EL84