Joyo Ultimate Drive v2  [schematic]

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Joyo Ultimate Drive v2

Postby alblupo » 15 Nov 2017, 23:20

Hi everybody. This is the first time I start a new topic (and post a schematic) so I hope not to make too many mistakes :oops:

As I was not able to find it in the internet I traced the schematic of the infamous Joyo Ultimate Drive v2 (2010-11-24 version).
here it is:
Ultimate Drive 2010_rev2.png

For your convenience I prepared two pictures with values and component naming. I cannot warranty the naming is 100% compliant with the PCB silkscreen, as reading under the resistors was in many case impossible, but at least the naming is coherent with the schematics.
Ultimate Drive names.jpg

Ultimate Drive values.jpg

And now some comments about the changes between the first and the second version.
My educated guess is that this redesign was mainly intend to avoid possible issues on the intellectual property of the circuit design, by adding a buffer, rearranging the clipper, and changing one (insignificant) resistor value.

The first difference with respect to the 2009 version is the buffer formed by Q1, C1, C2, R1, R2 and D1. It is one of the most simple and common MOS-FET buffer. The input impedance is well above 1.5M in all the audible range. The Zener Diode (I was not able to read the exact model, so I put a plausible device) should be a 9.1V model intended to protect the FET from electrostatics. It is quite interesting to note that many comments on the internet refer to it as a wrong implementation of the millennium bypass but I respectfully disagree. They simply decided to add a (quite transparent and simple) buffer.

The second difference is that the MOS-FETs and the Ge Diode in the clipping stage have been rearranged. I have to point out that I put the Ge Diode as it should be and not as apparently is from factory. When reversed (as from factory) the clipping stage formed by the D2 and Q2 does not work so only one half-wave is clipped (by Q3). If you want it to sound as it was intended to be, check D2 and swap it.

The last (insignificant) difference is that R8 was changed from 10k (value that is used both in the OCD and in the 2009 of the ultimate drive) to 470K. It can be useful to note that due to the circuit design this resistor is not necessary and should have no effect on the sound. On the contrary the higher value could increase the thermal noise of the pedal, but probably in no audible way (I made no test). Anyhow, moving it back to 10K could be an idea...

What is clear is that this the pedal is no more true-bypass as the buffer is in front of the switch. Anyhow the "old" input stage after the 3TDP switch is unchanged. If someone want to turn the pedal back to true-bypass, it should be pretty strateforward to modify the circuit by removing C1 and C2 (the large capacitors placed in between the jacks) and putting a jumper in between the two holes closer to the PCB border. Obviously different implementations are possible, including providing the pedal with two alternative inputs one buffered and one unbuffered, or modify the pedal in such a way that the switching include the buffer too, making it again true-bypass. But that is another story and shall be told another time.
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dv8r601 (17 Nov 2017, 05:46), karul (15 Nov 2017, 23:54)
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Re: Joyo Ultimate Drive v2 schematics

Postby alblupo » 16 Nov 2017, 02:30

I have to apologize. I spotted some errors.
Namely:
R1 is connected to Vcc/2
I was misinterpreting R4 as R8 in the circuit and swapping in the component placement. As a consequence of this I was swapping the clipping stage orientation.
Here the corrected files
Ultimate Drive 2010_rev3.png

Ultimate Drive names.jpg

Ultimate Drive values.jpg
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Re: Joyo Ultimate Drive v2 schematics

Postby howmuch » 16 Nov 2017, 03:10

Alberto, thanks for posting the complete schematic.
However, your clipping section is still not quite correct.
Check out my partial schematic of the clipping section here - Joyo - JF-02 Ultimate Drive "2010" MISTAKE
... and how to fix that diode.
Please check it again carefully. I think you'll find that the MOSFET gates are connected to the Sources, not Drains. That's true for the Joyo and the FT.
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Re: Joyo Ultimate Drive v2 schematics

Postby alblupo » 16 Nov 2017, 07:34

howmuch wrote:Alberto, thanks for posting the complete schematic.
However, your clipping section is still not quite correct.
Check out my partial schematic of the clipping section here - Joyo - JF-02 Ultimate Drive "2010" MISTAKE
... and how to fix that diode.
Please check it again carefully. I think you'll find that the MOSFET gates are connected to the Sources, not Drains. That's true for the Joyo and the FT.

Yes, you are right, I was swapping the direction by mistake. BTW your thread about the "mistake" was one of the main inspiration for this work
Here it is:
Ultimate Drive 2010_rev4.png

And thank for checking!
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Re: Joyo Ultimate Drive v2 schematics

Postby Chugs » 16 Nov 2017, 09:34

Presumably, C4 is meant to be 0.068uf?

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Re: Joyo Ultimate Drive v2 schematics

Postby alblupo » 16 Nov 2017, 11:07

Chugs wrote:Presumably, C4 is meant to be 0.068uf?

Yes 68n as reported in the component values picture... I will fix the typo asap. Let's wait if you spot other errors 8)
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Re: Joyo Ultimate Drive v2 schematics

Postby howmuch » 16 Nov 2017, 17:31

Referring to your Rev04 schematic, here's some more errors I think
Your C9 should be 1uF.
Your R8 is actually 10k.
There is an extra 470k to GND after the buffer's 1uF cap.

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Re: Joyo Ultimate Drive v2 schematics

Postby alblupo » 17 Nov 2017, 07:20

howmuch wrote:Referring to your Rev04 schematic, here's some more errors I think
Your C9 should be 1uF.
Your R8 is actually 10k.
There is an extra 470k to GND after the buffer's 1uF cap.

Yes you are right! I was naming R7 two of the 10K resistors! I will double check it again. About the 470k I have not fully understood were it should be connected, but for sure I missed something.
About C9, to me is a 10u electrolytic (it has the same size of C13 and it was reported 10u in the v1 too) but I will check it again.
I hope I can post a debugger version during the weekend.
Thanks a lot for the help
Alberto
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Re: Joyo Ultimate Drive v2  [schematic]

Postby alblupo » 19 Nov 2017, 10:43

Finally howmuch was right all the line! Thanks a lot for the useful help!
C9 and C13 have the very same size, but the first it 1uF 50V, the second 10uF 25V.
Here the updated versions of both the schematics and the component placement.
Ultimate Drive 2010_rev5.png

Ultimate Drive values.jpg

Ultimate Drive names.jpg

If can comment again, a part form the "reverse diode" issue, the circuit is basically identical to the OCD v3 (as the "changes I spotted in my previous comment were just bad circuit tracing).
the 470kohm resistor (R4) is simply the buffer output resistor. In this sense, the buffer can act as a anti-pop (as someone reported) as it warranty that during the switching all the caps are connected to the ground.

I think now it is quite accurate, but if you seen any other changes or have any doubt, please contact me so that I can further fix the schematics.

Not it is time for modding :)
One not to people that want to perform the Freakish blues mods. Due to the added buffer all the caps after the buffer are "+2" with respect to the v1 (true bypass version), and all the resistors are "+3" (e.g. R1=>R4 etc..).
Have fun!
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