Joyo - JF-05 Classic Chorus - volume decrease mod

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Joyo - JF-05 Classic Chorus - volume decrease mod

Postby andmarti1424 » 20 Jun 2018, 16:17

Hello. I am trying to decrease volume in this joyo chorus pedal (seems similar to ibanez cs9, but not exactly the same).

this is ibanez cs9 schematic (open the image completely):
Image

I have tried increasing R123 (3.9K) value to decrease dry signal.. (I actually used a variable preset), but this is not the behaviour I am after, since this change the mix of wet and dry signals..

I then though of changing R131/R141 (just one, since this is mono) 470R resitor to a higher valuer.. but it seems there is not that resistor in the output section..
27K (R130) and 91K (R129) are the two resistors at the left of the left 4558D IC.

this is joyo pcb (borrows image):
Image

then it goes to other resistors rather than the 470R one..
The resistor below the 4558D IC seems a 47K resistor..
the one below it could be a 570K.
then you have various 10K resistor.. then to a C2458 transistor / 473 cap.
Anyone know what is this arregement?
Any idea how can decrease volume?

Thanks for any help!
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Re: Joyo - JF-05 Classic Chorus - volume decrease mod

Postby plush » 20 Jun 2018, 17:13

I guess you should play with a feedback loop of the de-emphasis filter (r129/r132 on your schematic - just for reference).
Track your resistor with dmm (or using your eyes), since joyo schematic differs from ibanez CS9.
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Re: Joyo - JF-05 Classic Chorus - volume decrease mod

Postby andmarti1424 » 20 Jun 2018, 23:07

plush wrote:I guess you should play with a feedback loop of the de-emphasis filter (r129/r132 on your schematic - just for reference).
Track your resistor with dmm (or using your eyes), since joyo schematic differs from ibanez CS9.


thanks. actually I achieved the volume decrease with a voltage divider at the output.
i solder two legs of a 100k preset (could be a pot) to the 3pdt switch and the other preset leg to a wire to the pcb. cut a trace and thats all!

Result is just what I needed!
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Re: Joyo - JF-05 Classic Chorus - volume decrease mod

Postby AuditoryDriving » 21 Jun 2018, 04:11

it s a great pedal minus the hiss....
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Re: Joyo - JF-05 Classic Chorus - volume decrease mod

Postby plush » 21 Jun 2018, 09:41

andmarti1424 wrote:thanks. actually I achieved the volume decrease with a voltage divider at the output.


Yep, That's another option.
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