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7 Απρ 2018

Joyo JF-03 mods!



So I bought the JOYO JF-03 Crunch Distortion Guitar Effects Pedal from Thomann.de with the harley benton logo. It's basically the Joyo electronic board and housing with a different brand logo.

The pedal is well built and it sound really good. It's supposed to be a clone of the MI audio CrunchBox pedal. There's plenty of gain from this really simple two-stage circuit and the tone is marshall-like.
It's strongly based on the V.2 CrunchBox. The schematic diagram is shown below. However, the electronic component markings of the Joyo pcb and the schematic DO NOT match in most cases:

(Credit: http://revolutiondeux.blogspot.gr/2012/01/mi-audio-crunch-box.html )

There are many youtube demos available and the pedal is really worth a try for 30 bucks. However, I wanted to tweak its circuit a little bit in order to unlock its full potential and try a few different tones.



Let the mods begin!

-Different clipping distortion flavor:
This one is an easy & classic mod. The pair or red LEDs are responsible for clipping the boosted guitar signal. Replacing only one of these leds with a different color led or a diode (e.g. 1N4001) will lead to asymmetrical clipping which sounds more tube-like with richer harmonics. I simple bypassed the LED marked as D2 with a 1n4001 diode. The diode has a smaller forward voltage drop so you don't have to remove the red Led from the pcb. Just solder the diode across the led's legs. You don't even have to pay much attention to its polarity as the leds are wired back to back in parallel.


-Less bass and muddy response:
The goal here is to roll off a bit of low end in order to get a clearer british tone when using a guitar equipped with humbuckers. I replaced c4 and c5 capacitors with 0.1uF=100nF/63V film ones.

-Top Boost!
Rolling off a bit of bass leads to less gain but we can make up for it with a bit of top end boost! I simply replaced R4 (1K resistor) with a 680ohm 1/8W resistor.

-More lead!
-To get some extra gain and lead distortion, I replaced R5(10K resistor) with a 4.7Kohms 1/8W resistor.

-Treble adjustment: 
The pedal has a built-in presence trimmer control! I adjusted this one for less treble in order to get an amp-like response with less nasty/fuzzy high frequencies.


Cheers,
Thanos

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