The Soulsonic FX Fourbanger is a four-in-one boost pedal: four different booster circuits in one box, each of which can be switched in or out and stacked with the others. Soulsonic describes it as "the ultimate tweakers boost pedal" and says that with its combinations "it's like a dozen pedals in one!"1 For a player, that means one pedal that covers everything from a clean lift to stacked sounds the maker says range over overdrive, distortion and fuzz, all within the boost family1.
The four boosters
The four circuits are arranged in a fixed order. The blog author, IvIark, wrote: "I think the order Martin has the effects is Rangemaster (R), Mosfet (M), Opamp (O) and JFET (J)."1
| Stage | Circuit type | Notes |
|---|---|---|
| R (Rangemaster) | PNP transistor boost, negative ground | Substitutions reported include an OC44 for the Rangemaster transistor1 |
| M (Mosfet) | Mosfet boost | |
| O (Opamp) | Opamp boost, LF411 | 741 or TL071 believed usable as substitutes1 |
| J (JFET) | JFET boost, 2SK117 | 2SK880 used in current production per Soulsonic's website1 |
Each booster has its own gain or volume control and is turned on with a toggle switch. A single stomp switch then takes the whole lot in and out of circuit1. Because pushbutton switches let you choose any combination of the four, the pedal allows many stacked sounds on top of the individual boosts1.
Bypass and switching
The offboard wiring is essentially like a true bypass looper, with the signal going from the stomp switch to the first effects toggle and back through the chain1. In practice, the toggles decide which of the four boosters are in the signal path, and the stomp switch bypasses everything at once.
Building one: substitutions and versions
The Guitar FX Layouts blog published a stripboard (vero) layout for the Fourbanger on 12 February 20141. For anyone sourcing parts, the blog comments hold several reported substitutions:
- JFETs (J stage): the 2SK170 is described as very similar to the 2SK117. Builders have also used 2N5952s with the pins twisted and 2N5457s with the leads bent to fit1.
- JFETs, factory version: Soulsonic's website said the pedal was "now using 2SK880! WAY BETTER!" in place of the 2SK1171.
- Opamp (O stage): most usual single-channel opamps such as the 741 or TL071 should substitute for the LF4111.
- Other parts: one builder reported substituting a MAX1044 as the voltage converter and an OC44 for the Rangemaster transistor1.
There are two layout versions. The original Fourbanger used the Crackle Not OK version of the SHO circuit; the blog layout swaps in the original SHO circuit instead. A second layout of the original version, keeping the Crackle Not OK circuit, was added on request on 14 February 20141.
Builders' reports on the layout were positive. One builder traced a fault to a bad 4u7 capacitor and reported afterwards: "I had a bad 4u7 cap. It's awesome now!"1 Another noted that each of the four effects boosts the signal above the straight signal even at the lower settings, with single coil pickups1.
Questions
What are the four boosters in the Soulsonic FX Fourbanger?
The Fourbanger combines four boost circuits in one pedal: a Rangemaster-style boost built with PNP transistors, a Mosfet boost, an opamp boost built around the LF411, and a JFET boost built with 2SK117 JFETs. Pushbutton switches let you choose any combination of the four, and the maker says the stacked combinations produce sounds ranging over overdrive, distortion and fuzz.
Is the Soulsonic Fourbanger true bypass?
Yes. The offboard wiring is described as essentially like a true bypass looper, with the signal going from the stomp switch to the first effects toggle and back through the chain, so the whole pedal can be taken out of circuit with the single stomp switch.
What can replace the 2SK117 JFETs in a Fourbanger build?
The Guitar FX Layouts blog author suggests the 2SK170 as very similar to the 2SK117. Builders have also reported using 2N5952s with the pins twisted and 2N5457s with the leads bent to fit the board. Soulsonic's own website said it was using 2SK880 instead of the 2SK117 in current production.
Can another opamp replace the LF411 in the Fourbanger?
Yes. The blog author believes most usual single-channel opamps such as the 741 or TL071 can be substituted for the LF411 in the opamp boost stage.
What is the difference between the original and the blog layout versions?
The original Fourbanger used the Crackle Not OK version of the SHO circuit for one of its stages. The Guitar FX Layouts version swaps in the original SHO circuit instead. A second layout of the original version, with the Crackle Not OK circuit, was added to the blog on request two days after the first layout appeared.
Sources (1)
- Guitar FX Layouts: Soulsonic FX Fourbanger, Guitar FX Layouts (tagboardeffects.blogspot.com), 2014-02-12
