Joyo - JF-13 AC Tone  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.

Re: Joyo - JF-13 AC Tone

Postby Mickyvai » 12 Mar 2016, 18:06

Hi everyone. I performed the speaker sim mod and thought that someone here could use a schematic of the mod that was previously explained, with all the details specified. ;-)
You do not have the required permissions to view the files attached to this post.

For this message the author Mickyvai has received thanks:
MACopeland90 (01 Apr 2016, 02:12)
Mickyvai
 
Posts: 2
Joined: 25 Jan 2013, 12:58
Has thanked: 0 time
Have thanks: 1 time

Re: Joyo - JF-13 AC Tone

Postby Mickyvai » 16 Mar 2016, 11:39

I have done a short demo of the mod:

[youtube]https://www.youtube.com/watch?v=KjLntLSirn0&feature=youtu.be[/youtube]
Mickyvai
 
Posts: 2
Joined: 25 Jan 2013, 12:58
Has thanked: 0 time
Have thanks: 1 time

Re: Joyo - JF-13 AC Tone

Postby ericlaw02 » 20 Jul 2016, 11:45

Has anyone traced the full schematic of the Joyo circuit for differences against the Tech21 originals (http://www.freestompboxes.org/viewtopic.php?p=220001#p220001), other than the R4/E1/Cin/C2... components?

I replaced the components to create my own "VT Bass", the tone seems identical to YouTube videos with each setting, but it seems lacking in gain, and with noticeable increase in noise.

For example, an actual VT Bass unit can achieve unity gain when EQ is flat, drive at 10 o' clock, when level is set to 8-9 o' clock, yet on my modded Joyo, I have to turn to around 2-3 o' clock to achieve unity gain. So somewhere there's at least some difference between the two circuits.

For starters, I checked the circuit/component values after the final opamp output, and they seemed identical, so it's not that simple unfortunately :(
ericlaw02
 
Posts: 5
Joined: 14 Sep 2015, 07:08
Has thanked: 2 times
Have thanks: 5 times

Re: Joyo - JF-13 AC Tone

Postby ericlaw02 » 20 Jul 2016, 19:06

I think I may have answered my own question about the lack of gain.

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 know nothing about electronics, but I suppose R31 is the culprit for the lack of gain, replacing it should allow me to match the original's levels. Though I don't really think that's going to help reduce the noise...?

Still, I'm interested if anyone found out any other differences between the two boxes...
ericlaw02
 
Posts: 5
Joined: 14 Sep 2015, 07:08
Has thanked: 2 times
Have thanks: 5 times

Re: Joyo - JF-13 AC Tone

Postby Hanky- » 07 Aug 2016, 06:44

ericlaw02 wrote:I think I may have answered my own question about the lack of gain.

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 know nothing about electronics, but I suppose R31 is the culprit for the lack of gain, replacing it should allow me to match the original's levels. Though I don't really think that's going to help reduce the noise...?

Still, I'm interested if anyone found out any other differences between the two boxes...


I found that R31 measured 22k on the actone while the california sound had 68k in that place.but the calif has added mic sim components which lower the overall volume so removing those to match the actone gave me significant increase in volume.

After trying out different values in R31, 47k sounded good to me without affecting the tone much or the dynamics. My guess with the noise in joyo is the buffer design might be the culprit since it isn't the same as the tech 21 or perhaps maybe it's the board quality in the joyo being sub par. I even replaced the ICs to match the tech 21 but it didn't lower the overall noise.

For this message the author Hanky- has received thanks: 2
ericlaw02 (08 Aug 2016, 06:43), HENK (07 Aug 2016, 08:35)
Hanky-
 
Posts: 15
Joined: 22 Jul 2015, 08:51
Has thanked: 0 time
Have thanks: 3 times

Re: Joyo - AC Tone

Postby pjk » 01 Jun 2017, 22:29

Ripdivot wrote:Remove the part shown and add a jumper wire duplicating the switch in the down position.


Hi and thanks very much for doing this. If i am not wanting to add the switch, does the jumper wire go from pin 3 on the volume pot to R24 or is it to the point adjacent to the 0 ohm resistor please ?
pjk
 
Posts: 1
Joined: 31 May 2017, 14:49
Has thanked: 1 time
Have thanks: 0 time

Previous

Return to Modern Stompbox Effects (1975 - ...)

Who is online

Users browsing this forum: Bing [Bot] and 13 guests