Xotic - Soul Driven  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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harmaes
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Post by harmaes »

I haven't played it and haven't bought one yet but I hear from my fellow demonstrators that it's behaving like a Zendrive with a mid boost.

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Post by mlp-mx6 »

There are some (at least partial) gut shots on these pages:

https://www.digimart.net/magazine/artic ... 02318.html
https://www.ikebe-gakki.com/ec/pro/disp/1/515702
http://benimarulabo.com/xotic-soul-driv ... len-hinds/

SMD transistors say "2CW" which is BC849C (or CW). I can't make out the opamp - resolution is too low. And cannot see the film cap values at all. The 2 diodes sure look like 4148s.

I really like the sound of this pedal. WAY overpriced, though, IMHO.
515702_sub_3_l_201705081335.jpg
DSC01911-e1482466489627-1024x453.jpg

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Ichabod_Crane
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Post by Ichabod_Crane »

Bump!
harmaes wrote:I haven't played it and haven't bought one yet but I hear from my fellow demonstrators that it's behaving like a Zendrive with a mid boost.
Here's a gut shot from a video:

[ Image ]
https://dl.dropboxusercontent.com/u/224 ... Driven.jpg
Very interesting pedal. I don't know well the Zendrive (it has the Voice pot, the Xotic hasn't it).
The Ibanez ST-9 Super Tube Screamer has a mid control. It could be useful to know it.

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Post by aion »

Schematic attached. This is a new OD from Xotic developed in collaboration with Allen Hinds as a signature drive pedal, released in 2016 or so.

Full tracing log including photos here:
https://aionelectronics.com/blog/tracin ... overdrive/

And a PCB available here:
https://aionelectronics.com/project/thu ... overdrive/
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xotic-soul-driven-trace-schematic.png

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Chugs
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Post by Chugs »

Interesting, sort of like a Zen Drive-ish front end with Bass boost section is taken from the Boss BD-2 followed by a transistor output buffer.

Topology/values for the bass boost section match the BD2 but with switchable boost. Same diode protection and preceding volume control.

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Post by george giblet »

I'm not convince the bass switches are correct.

I've built a number of post bass-boost circuits like that and with a 18k+15k+10k in series the bass boost is enormous. The Boss BD-2 only has 6.8k.

The specs say Flat (0dB), +2.4dB,+3.6dB, +6.0dB.

At first I thought 0dB could be when the feedback resistors are entirely shorted but that brings up a problem with the +2.4dB range since with the lowest combination of 18k//15k//10k the boost is a lot more than +2.4dB.

So the next idea was 18k//15k//10k was the 0dB mark then each dip switch disconnects one of the resistors.

If you look at the tracks:
- 18k and 15k are connected together
It's also possible this same track follows under the switch and to the 10k then down to the 10uF electrolytic.
- switch 1 looks like it goes to 15k
- switch 2 looks like it goes to 10k

So the simplest scenario where that holds together is when the 18k is permanently connected and the 15k and 10k are connected in parallel with the 18k. The difference in level between in the least boost "0dB" with 18k//15k//10k and 18k is 7dB so it's not quite there. The difference between 15k to 18k//15k//10k is more like 6dB but the other steps don't quite match-up with the spec. Some more elaborate combinations give better matches but they don't seem feasible with the simple dip switch.

You can't always believe the printed specs but the common track certainly looks a more convincing argument.

Anyway, it's something to think about. Really needs checking on a real unit.

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Post by aion »

george giblet wrote:I'm not convince the bass switches are correct.

I've built a number of post bass-boost circuits like that and with a 18k+15k+10k in series the bass boost is enormous. The Boss BD-2 only has 6.8k.

The specs say Flat (0dB), +2.4dB,+3.6dB, +6.0dB.

At first I thought 0dB could be when the feedback resistors are entirely shorted but that brings up a problem with the +2.4dB range since with the lowest combination of 18k//15k//10k the boost is a lot more than +2.4dB.

So the next idea was 18k//15k//10k was the 0dB mark then each dip switch disconnects one of the resistors.

If you look at the tracks:
- 18k and 15k are connected together
It's also possible this same track follows under the switch and to the 10k then down to the 10uF electrolytic.
- switch 1 looks like it goes to 15k
- switch 2 looks like it goes to 10k

So the simplest scenario where that holds together is when the 18k is permanently connected and the 15k and 10k are connected in parallel with the 18k. The difference in level between in the least boost "0dB" with 18k//15k//10k and 18k is 7dB so it's not quite there. The difference between 15k to 18k//15k//10k is more like 6dB but the other steps don't quite match-up with the spec. Some more elaborate combinations give better matches but they don't seem feasible with the simple dip switch.

You can't always believe the printed specs but the common track certainly looks a more convincing argument.

Anyway, it's something to think about. Really needs checking on a real unit.
Here's a gallery of another set of tracing photos -


The resistor numbering translates as:
My schem R6 -> their R19
My R16 -> their R15
My R17 -> their R18

I didn't end up removing any components from the board during the trace, so I can't verify for sure that the trace underneath the DIP switch is exactly as shown in the schematic. But, I can say 2 things -

1) My clone based on the above schematic definitely does not have too much bass - it's pretty modest over the full range of the knob and doesn't sound like much more than 6dB of gain across the range. This is purely anecdotal though and should not be construed as proof one way or the other.

2) It does seem pretty strange to put resistors in parallel for a DIP switch setup, when you could just use the combined resistor value instead. You could implement some pretty tricky/elegant solutions this way when combining parallel values vs. series values, but it just seems a little 'beyond' Xotic to have galaxy-brain ideas like that when they are historically more of a cut-and-paste shop.

Speaking of which - good catch on the Blues Driver. The back half of the circuit is identical to the BD-2 except for a couple of different values, starting with the tone control through to the output. I hadn't studied the Blues Driver enough on its own to recognize that part of it out of context.

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Post by george giblet »

Here's a gallery of another set of tracing photos -
Excellent thanks.

From those pics I can see the underside of the board. There's not a lot going on under there
which reduces down the number of possibilities by a large factor.

There's +V power rail running under the dip-switch (violet line on my attached pic) which isolates the top part of the dip switch. So the top part of the dip switch connects together

After that it all falls into place and I can see your schematic is fine. BTW, there's a wire missing on your schem which joins the top of the dip-switch.


I didn't end up removing any components from the board during the trace, so I can't verify for sure that the trace underneath the DIP switch is exactly as shown in the schematic. But, I can say 2 things -

1) My clone based on the above schematic definitely does not have too much bass - it's pretty modest over the full range of the knob and doesn't sound like much more than 6dB of gain across the range. This is purely anecdotal though and should not be construed as proof one way or the other.

2) It does seem pretty strange to put resistors in parallel for a DIP switch setup, when you could just use the combined resistor value instead. You could implement some pretty tricky/elegant solutions this way when combining parallel values vs. series values, but it just seems a little 'beyond' Xotic to have galaxy-brain ideas like that when they are historically more of a cut-and-paste shop.

Speaking of which - good catch on the Blues Driver. The back half of the circuit is identical to the BD-2 except for a couple of different values, starting with the tone control through to the output. I hadn't studied the Blues Driver enough on its own to recognize that part of it out of context.

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Post by george giblet »

Sorry I accidentally hit submit and I can't edit.
1) My clone based on the above schematic definitely does not have too much bass - it's pretty modest over the full range of the knob and doesn't sound like much more than 6dB of gain across the range. This is purely anecdotal though and should not be construed as proof one way or the other.
I had a listen to some demo videos and it didn't' sound too bassy. Perhaps a tad bassy on the max setting.
Speaking of which - good catch on the Blues Driver. The back half of the circuit is identical to the BD-2 except for a couple of different values, starting with the tone control through to the output. I hadn't studied the Blues Driver enough on its own to recognize that part of it out of context.
The Bad Monkey is another one with that structure, but different parts.. There's a few others out there. The earliest example is perhaps the Morley Diamond distortion but that uses a shelving EQ not a peaking EQ, which doesn't sound as good.
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Xotic SD traces.jpg
Xotic SD traces.jpg (64.52 KiB) Viewed 4295 times

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Post by aion »

george giblet wrote:BTW, there's a wire missing on your schem which joins the top of the dip-switch.
Right you are. I corrected that and attached the updated schematic.
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Xotic Soul Driven - schematic v1.1
Xotic Soul Driven - schematic v1.1

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Post by Flaconsius »

I was hoping that this Circuit appear traced sometime. Thank you, guys.
It is a very cool Overdrive and a really interesting circuit to analize. Even when it is still a YATS, it has some little tricks to "watch and learn".

Maybe the part that called the most of my attention is the Fixed-Gyrator thing, before the second Opampd, wich is Copypasted from the Blues Driver.
In a Gaphic EQ, the Gyrators are the same, but they are connected to the Middle Lug of a linear Potentiometer, wich has its other Lugs to each Input of the OpAmp.
Such like this:
Image

I input those values in the AMZ Gyrator Calculator and it gave a Frequency of 120Hz, with a Q Factor of (almost) 20. :block:

Here, the thing is different for having those Diodes instead of a Potentiometer.
My guess is that the Diodes lower the signal in 0.6V, in both Hemicycles, so that equals a "slightly turned up Potentiometer" causing a little (or not so little) Boost in that Frequency. :scratch:

Having that in mind, there are two basic (and interesting) Mods to make:

1- Replacing the Diodes by the typical Potentiometer.
2- Changing the 470k Resistor Value, via a Switch or a Pot. So you can Boost (or cut in case you replaced the Diodes for a Pot) other Frequecies. :horsey:
In the AMZ Gyrator Calculator, I replaced the 470k Resistor by 100k. The result is 260Hz with a Q Factor of 9. Pretty interesting for a Low-Mid Presence 8)

Those werre my 2 Cents. Hope not being wrong and have contributed with something.

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Post by Flaconsius »

Well, Friends, sorry for the double Post, but I like to keep things in order:

Another diyer in a Facebook group simulated this and the results are what I had thougt. :mrgreen:
Changing the 470k Resistor for 33k the Freq Peak is in 450Hz:
Image

And, if you want the Typical TS9 Highmid Peak, change the 470k Resistor for 220k and the Cap that connects to the Base of the Transistor, for 3n3.
Image

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