JOYO JF-13 AC Tone Guitar Effect Pedal DI Amp Sim

Product Information

I did a similar approach, but used a 1M pot in series with the wire from R24 to the “off” side of the SPDT switch. On the original Tech21 schematic, with R19=10k and R20=100K, IC3a provides 10x voltage gain (20db gain). But on the Joyo, the corresponding components being R30=10k and R31=15k, it should only provide 1.5x voltage gain (~3.52dB gain). I used a SPDT switch, some fine wire-wrap wire, and a tiny bit of good ol' lead-tin solder with flux.

I would not say that the AC Tone has more treble than both the others. If you matched the amplitudes at 1kHz (a reference no better than others) with the Voice control at mid-point, it actually has less treble ... But in all cases, you still have +/- 12dB on tap in each EQ band. C14 - .115uf This value is wrong (would cut all treble and most mids), i had the same problem. I guess that the input impedance of the unpowered opamp screws up the capacitance measurement there. Let's assume it's 470pF like the Blonde.

I forgot to say that each pedal has three curves, corresponding to the Voice/Character control set at 0, 5 and 10. But the amplitude would never reach the theoretical maximum, because of clipping in the following gain stage. I've made this mod to all four of the Joyos. The Actone, American and British are all very similar, but the California model has some different circuitry. This is all four in bypass mode: Thanks again for your work on the new pcb-layout - now it is a very versatile component of my pedal-board. The AC Tone is a complete amp/cabinet simulator and ideally should be fed straight into a full-range acoustic amp or PA/mixing-desk. A guitar amp will add further colouration -- so you are right to set the tone of the guitar amp as flat as possible.

I confirm it to be the same circuit as the Tech21 Character Series, but this one is kind of a mix between a Liverpool and a British. Probably somewhere around Birmingham. In terms of construction the JF-13 is made from durable aluminium and has a incredibly sturdy design. Its true bypass footswitch means that you don't lose any tone when the pedal is off. The pedal runs of a 9v battery or 9v power supply. Hi, thanks for that. I did it on my American Sound (Harley Benton, not a Joyo, but the pcb is the same). It works great. One important difference with modding the California is that the "0" surface mount resistor is instead 2.2k ohm resistor, and I did not remove it, and the mod works fine with that 2.2k resistor just left in place. It's not true-bypass, but you don't care because the opamp before drives your signal with an appropriately low impedance.

The thing with the Joyo AC Tone is if you are using it with an amp, set the amp to the sound you like fo what you are wanting to play with the pedal off, then use the pedal to change the tone to another sound. That means that you effectively have two different sounds. For example if I were to use my Vox AC-30 non Top Boost, I'd get the old 1960 sound on that, then add the Joyo to give me the Top Boost 1964 sound at the press of a switch. The other way round if I used by Top Boost amp, I'd set the amp to give the sound of 'Flingel Bunt' and compensate using the Joyo to get the old 'Apache' sound by removing the bass and some treble and adding the mid, wth the 'voice' and 'drive' to taste. If your hand is steady enough and the tip of your soldering iron fine enough to work with SMD, yes it is.

E1 is measured as 22n, compared to 18n in the British and 27n in Liverpool. This might be a matter of tolerances, though. Mine has a dull yellow color, not the nice gold finish of newer units. However, the PCB is identical to the pictures above.

C21 - .016uf Should be 10nF in a Blonde. This and the one above shift the mid-EQ frequency towards bass, about 550Hz instead of 900Hz Here are a small "map" of where those components are if you want to tweak them, and a simulation of the frequency responses of the British, Liverpool and AC Tone. Disclaimer : This is an attempt to recreate my previous posts in the "Character Series" thread that were lost in the server move. If your memory is better than mine, please comment. To get the right value of the resistor I soldered two lugs of a 10k-pot instead of a fixed resistor and turned it as long as I got nearly the same volume in both positions. Then I disoldered the 10k-pot again and measured the resistance between the affected two lugs. In my case it was around 3k3. So I soldered a fixed 3k3 resistor instead of the 10k-pot and it works great in all positions of the Volume-pot. Maybe values between 2k2 to 3k9 will work. Just have a try or do it with a potentiometer like I did. Steven_M wrote:As you can see from the graph above, the AC tone does more treble than both the British and Liverpool Tech 21 counterparts.

Ripdivot wrote:I had some time so I sat down and figured out the speaker sim bypass on the newer PCB. So in bypass mode, three of them are essentially the same pedal, and even when the cab sim is activated, the frequency response plots are still not dramatic. The California model though, has a significantly different response curve. One visual piece of evidence that they differ is the "C6" electrolytic capacitor is present in the California, but is missing from the other three models. Remove R29, it should be 6.2k in value. That should get the mic sim to be less present when doing the cab sim bypass on the California sound. R28 measured 22k on mine, I wonder if they changed that value lately. C14 is unknown, as i could not measure it accurately. It reads 9.6nF, which is wrong. I assumed 180p as in the Liverpool. The protection diodes are there, even if the opamp are now TL064 instead of static-sensitive rail-to-rail CMOS devices. The jumpers and open spots are there too. Despite the "True Bypass" label next to the 3PDT footswitch, there is a (presumably JFET source follower) bypass buffer. The SMD SOT-23 chip has "12W" making, it might be a 2N7002 MOSFET. Or something else.The various echo-machine simulators don't just create echo patterns -- they also simulate the preamp(s) in the original echo-machines so, to get the full effect, they really need to be placed before the AC Tone. R7 is 100k as in the British. This makes a huge difference in frequency response, as the open-circuit there in the Liverpool creates a big hi-pass slope. I used 26AWG wire for my connections. Start by removing the 0 ohm resistor shown. Solder a wire to each of the three places shown in red. Once your wires are in place put a small blob of hot glue over the connections to the board. I didn't do this to the wire soldered to pin 3 of the level control as it is plenty solid. solder the other end of the three wires to your switch and you are good to go. Works great!