Joyo - JF-13 AC Tone  [schematic]

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Joyo - JF-13 AC Tone

Postby Steven_M » 29 Jun 2011, 22:02

I think we all pretty much know what this is, but as I have one sitting here, I thought I'd take a few shots.

Outside.JPG

Outside is actually a really nice gold finish. Not at all cream, the way it looks on the website
Switch.JPG

I've seen this somewhere before... Not great soldering on the wires. I might have to beef that up.
Inside1.JPG

Underside Shot
Inside2.JPG


All of the pots that control EQ are 100Kb. I'll get some better pictures up once I get home.

Also, here is the shot from the TECH21 Character series thread:
26062011 003s.jpg
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Re: Joyo AC Tone

Postby HENK » 30 Jun 2011, 11:32

NICE!
From the German Forum:
-R4:10K
-R14:33K
-R7:100K(NOT IN THE ORIGINAL!)=more Bass in lower Character/Voice-Settings.
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Re: Joyo AC Tone

Postby HENK » 30 Jun 2011, 11:39

HENK wrote:NICE!
From the German Forum:
-R4:10K
-R14:33K
-R7:100K(NOT IN THE ORIGINAL!)=more Bass in lower Character/Voice-Settings.

-I.C.s:TL062.
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Re: Joyo AC Tone

Postby Intripped » 30 Jun 2011, 12:14

hi,
what is the 51R resistor on the switch-pcb for?
a new solution for led-popping maybe?
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Re: Joyo AC Tone

Postby Steven_M » 30 Jun 2011, 17:29

Intripped wrote:hi,
what is the 51R resistor on the switch-pcb for?
a new solution for led-popping maybe?


I had that question myself. 51R isn't going to stop much in the way of pops, plus it looks like it is just connecting the bypass portion of the switching. Kind of like a jumper. With such a low value I'd assume that is what it's doing, although that begs the question of why it is needed at all.
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Re: Joyo - AC Tone

Postby guycapuano » 24 Jul 2011, 00:39

So is it a liverpool clone? Does it have speake simulation? :scratch:
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Re: Joyo - AC Tone

Postby Steven_M » 24 Jul 2011, 05:12

guycapuano wrote:So is it a liverpool clone? Does it have speake simulation? :scratch:

Yes. This is a Liverpool clone. If it's a direct clone, then it probably does have it. If you check an eBay auction or the joyo site, I'm sure they will list this fact.

Just for reference this pedal is very treble heavy. Much more so than the Liverpool is.
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Re: Joyo - AC Tone

Postby JiM » 03 Sep 2011, 18:21

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.

I recently bought a Harley Benton AC Tone, which happens to be a Joyo rebranded by Thomann.de.
Mine has a dull yellow color, not the nice gold finish of newer units. However, the PCB is identical to the pictures above.
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.

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.
Please note that the capacitor values were measured in-circuit, and are not very accurate.

Here are the differences :
  • R4 is 10k as in the British (3.3k for Liverpool)
  • E1 is measured as 22n, compared to 18n in the British and 27n in Liverpool. This might be a matter of tolerances, though.
  • C5 and C6 are both 22n, as in Liverpool. Those set the frequency of the Voice (aka Character) control.
  • 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.
  • R14 is 33k, like the British.
  • C14 is unknown, as i could not measure it accurately. It reads 9.6nF, which is wrong. I assumed 180p as in the Liverpool.
  • C15 is measured close to 4.7nF, compared to 2.2n in the British and 2.7n in the Liverpool.
  • C20 and C21 are respectiviely 18n and 22n, consistent with the Liverpool.

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.
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Re: Joyo - AC Tone

Postby atreidesheir » 03 Sep 2011, 18:48

Could anyone give us your impression of its sound?
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Re: Joyo - AC Tone

Postby Steven_M » 05 Sep 2011, 20:31

atreidesheir wrote:Could anyone give us your impression of its sound?

It sounds pretty good. Some of the settings are very treble heavy. As you can see from the graph above, the AC tone does more treble than both the British and Liverpool Tech 21 counterparts.

I have gotten some great tones from this thing. Well worth the $35 I spent on it. Some of the tones are less useful, but I was able to dial in both Brian May and the Edge tones, which is pretty much what I bought it for.
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Re: Joyo - AC Tone

Postby JiM » 05 Sep 2011, 23:08

atreidesheir wrote:Could anyone give us your impression of its sound?

I like it, even if i chose this model just for the pun on acetone. The active EQ is very effective, you can really dial the sound you want. If you find it "treble heavy", just turn the treble knob down. But it's not a problem for me, as my SG has quite a dark tone. The Voice knob is really the secret weapon, try to "opposite match" this one and the mid knob for a consistent response, but a varying amount of "grit" in the overdrive.
With voice, gain, bass and treble dimed, and mids at zero, you'll get an impressive metal sound. On the contrary, you can dial pretty thin old-radio sound when cutting bass, voice and gain, and boosting mids. There are many useable crunches and rock overdrives in beteween.

This configuration should be more versatile than the proper Liverpool : you can still cut the bass, but not obliged to. And it's high-end response is still distinctive compared to the "usual" Marshall sound.

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.

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 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.

I'm thinking of a way to get all three pedals in one. To mimic the Liverpool, just lifting R7 should do the trick. To turn the AC Tone into a British, 6 components values have to be changed, but maybe most of the tonal change could be achieved with 4 or less ... I'll need some 4P3T on-on-on switch.

Oh, and bypassing the speaker simulation provides a good boost in volume and in treble. I still don't know what i prefer when plugged into an amp, i'll have to do more testing.
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Re: Joyo - AC Tone

Postby Steven_M » 06 Sep 2011, 05:02

Is it easy to disable the speaker sim?
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Re: Joyo - AC Tone  [schematic]

Postby JiM » 06 Sep 2011, 22:19

Steven_M wrote:Is it easy to disable the speaker sim?

If your hand is steady enough and the tip of your soldering iron fine enough to work with SMD, yes it is.
I used a SPDT switch, some fine wire-wrap wire, and a tiny bit of good ol' lead-tin solder with flux.
The tricky thing is to lift the zero ohm next to C15 (at least the lower end as seen above), and to solder the wires to the empty pad below it, to the empty pad next to the volume pot (center of the switch), and to R14 (lower end).
It's not true-bypass, but you don't care because the opamp before drives your signal with an appropriately low impedance.

Tin the pads before use, while the flux is still fresh you can tack the wire in the blob, hopefully this will form a good solder, not a cold one.
Do not run you iron too hot (hence the leaded solder), and be quick, or the copper pads may de-laminate. Although this PCB seems to be better than those in Behringer stompboxes in that respect.


You wouldn't see anything interesting if i posted gutshots, because i gooped it.

:shock:

No, it's not what you think. I've used a few drops of translucent hot glue to make sure that the wires won't come off, i don't trust such a tiny blob of solder from a mechanical point of view. I did also use that to add some stress relief on the ribbon to the footswitch, it's a breakdown waiting to happen, just waiting for your next gig.

By the way, the jumper and the empty pads after the speaker sim could be used to host a "miked cab" simulation (aka bridged-T filter), just like the SansAmp GT-2.

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Re: Joyo - AC Tone

Postby cuthbertg » 07 Sep 2011, 05:12

Fantastic!

I had a surprise in the post today - an Ultimate Drive (which I'm going to put a 4pdt switch in for the FB mods) and the American sound pedal, and the only thing that's been really bugging me is wanting to see what it's like without the speaker sim.......
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Re: Joyo - AC Tone

Postby JiM » 07 Sep 2011, 21:39

cuthbertg wrote:I had a surprise in the post today [...] the American sound pedal

Could you please report the values of the components highlighted on the gutshot above, to check if it's a straight copy of the Blonde, or again a slight variation ?
For the resistors it's written on them, but for capacitors you'll need a multimeter with cap-meter feature. No need to de-solder them, I found in-circuit measure to be not so inaccurate for most interesting components. Just plug a couple of wires in the test slots, and touch both ends of the SMD chips with them.
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Re: Joyo - AC Tone

Postby cuthbertg » 07 Sep 2011, 22:36

JiM wrote:
cuthbertg wrote:I had a surprise in the post today [...] the American sound pedal

Could you please report the values of the components highlighted on the gutshot above, to check if it's a straight copy of the Blonde, or again a slight variation ?
For the resistors it's written on them, but for capacitors you'll need a multimeter with cap-meter feature. No need to de-solder them, I found in-circuit measure to be not so inaccurate for most interesting components. Just plug a couple of wires in the test slots, and touch both ends of the SMD chips with them.


No problem at all, it will be a pleasure to give something back to the community at last. Gimme a couple of hours though, I got a few things I need to do first :thumbsup
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Re: Joyo - AC Tone

Postby cuthbertg » 08 Sep 2011, 00:13

OK,

I hope this helps - I didn't take any readings from the gooped module area - let me know if you need anything...


R4 - 10k
R7 - 100k
R9 - 3.3k
R14 - 33k

C2 - .043uf
C5 - .021uf
C6 - .015uf
C14 - .115uf
C15 - .002uf
C20 - .016uf
C21 - .016uf
E1 - Not present

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Re: Joyo - AC Tone

Postby JiM » 08 Sep 2011, 21:28

Thanks cuthbertg for your quick answer !

Hmmm ... again, it's not a straight copy. :wink:

R4 - 10k Expected value
R7 - 100k Expected value
R9 - 3.3k Like the British and Liverpool, it would be 1k for a Blonde. This changes the slope of the Voice control when reduced, shifting the center frequency towards bass
R14 - 33k Again, similar to the British.

C2 - .043uf Close enough to the expected 47nF
C5 - .021uf Close enough to the expected 22nF
C6 - .015uf Should be 22nF in a Blonde
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.
C15 - .002uf Close enough to the expected 2.2nF
C20 - .016uf Should be 10nF in a Blonde
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
E1 - Not present Expected value

According to a quick Spice simulation, I suppose that the Joyo American Sound has slightly more treble than the Tech21 Blonde (can easily be compensated with the Treble pot), and it's Mid and Voice controls are set more in the lo-mids range.
Depending on you guitar, amp, and taste, it might sound better or worse, or about the same.

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Re: Joyo - AC Tone

Postby cuthbertg » 12 Sep 2011, 11:24

I have never played the Blonde, but with my setup, the American sound does work really well. I have a little Champ 600 with the fixed tonestack removed and use this and a reverb pedal in front of it and to my ears it does really bring the whole setup to life - so much so that the amp now does not sound as good without it...

It can be a bit trebly, but that's what the knob is for right! :thumbsup


I want to try to add a switch for the speaker sim bypass though, and as this is my first muck-about with SMD, I think I'll go and practice on some old PCI cards I have lying about first....you never know, If I get enough confidence and can find the right value components I may try changing the values so that it's a direct Blonde clone :mrgreen:

I do have a question though JiM, about the instructions - I'm not sure what you mean by: "the empty pad next to the volume pot "

could you just confirm which one you mean....?

Perhaps I just can't see the wood for the trees, but i would appreciate any help you could give..

I have attached an edited pic - Red rectangle=remove component....Red circle=tack a wire on here..
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Re: Joyo - AC Tone

Postby JiM » 14 Sep 2011, 19:40

cuthbertg wrote:I want to try to add a switch for the speaker sim bypass though, and as this is my first muck-about with SMD, I think I'll go and practice on some old PCI cards I have lying about first....

That's a very good idea. :thumbsup
But bear in mind that old cards were made with non-RoHS, lead-based solder which is a bit easier to work with (lower melting temperature).

cuthbertg wrote:I do have a question though JiM, about the instructions - I'm not sure what you mean by: "the empty pad next to the volume pot "
could you just confirm which one you mean....?
[...]
I have attached an edited pic - Red rectangle=remove component....Red circle=tack a wire on here..

You"re right so far. Here is an updated picture, with red dots for connexion points and red X for dis-connexion point. I've just lifted one end of the zero ohm resistor, but you can remove it completely if you want.
The center lug of the SPDT switch goes to the point you were asking for, closest to the volume pot : this is the one connected to the non-grounded end of the pot.
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