Catalinbread - Pareidolia Harmonic Mesmerizer  [traced]

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roseblood11
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Post by roseblood11 »

KindaFuzzy wrote:
mrkaploca wrote: Cool! But could this be 7805 regulator(it is not so visible on the image,or it is sanded out ? ).
Nope, it says 78m09b for sure, I haven't looked at that section at all to see how it works with a battery though.

It's just used as a overvoltage protection, I guess.

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KindaFuzzy
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Post by KindaFuzzy »

coldcraft wrote:2206D (as in XR-2206D) is a function generator. That's most likely their LFO
I agree, I just some in the mail yesterday for when I test the schematic.

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Post by KindaFuzzy »

Here's a little update, I started tracing it, but it was such a confusing layout that I decided to do a component trace first. Green is topside, purple is underneath. Looks like the raw DC from the battery or jack goes straight to the FETs, but has to get through the regulator to go to the two ICs. With a 9v battery that reads 9.8v out of circuit powering everything, the voltage feeding the regulator drops to 7.6v, and reads 6.1v after. With a 12v adapter, everything is as it should be, with 12v before the reg, and 9v exactly after.
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pareidolia.JPG

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Post by roseblood11 »

Interesting. Does the 2206 work properly with 6.1V?

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Post by KindaFuzzy »

roseblood11 wrote:Interesting. Does the 2206 work properly with 6.1V?
It was working when I first got the pedal and was testing it with a battery only, I'll double check the voltages when I get the jacks soldered back in.

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Post by KindaFuzzy »

Here's the schematic I came up with. Still have to test it on the breadboard, but looks good so far.
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pareidolia schem 2.JPG
pareidolia schem.JPG

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coldcraft
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Post by coldcraft »

interesting, although I'm starting to get some ideas about how it could be improved.
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Post by roseblood11 »

Another imperfect pedal with a perfect sound... :wink:

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Post by RnFR »

more mu-amps!
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Post by mysticwhiskey »

Image

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KindaFuzzy
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Post by KindaFuzzy »

Got the circuit working on the breadboard and sounding identical to the original, so schematic verified. Things learned:

1. This thing eats batteries, and if the voltage sags just a little, the 2206 stops oscillating or acts weird.
2. The 270p input cap makes a big difference, a 330p sounds terrible, and 220p sounds much better
3. It's really picky about the FETs, since there's no mix control between the two sides, you have to use 4 of the same type of FET to balance everything, and J201s have too much gain, while MPF102 doesn't have enough gain. I only had three 2n5485s and ended up putting a 2sk30 in the treb side and it was ok.
4. This pedal works even better without the 7809. It would probably be more reliable, and still protected from over voltage with a 9v zener or something, with a simple dropping resistor and an extra filter cap to supply the chips to keep the thumping out of the circuit.

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Post by Matt Gnarly »

Nice work Fuzzy! I've been really interested in this pedal and eventually I'll have to get around to building one.

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Post by coldcraft »

KindaFuzzy wrote: 4. This pedal works even better without the 7809. It would probably be more reliable, and still protected from over voltage with a 9v zener or something, with a simple dropping resistor and an extra filter cap to supply the chips to keep the thumping out of the circuit.

the 7809 is probably there to let you run the fets at 18v. fixing the Vcc of the function gen chip most likely keeps the modulation range and depth the same regardless of 9v-18v operation. a 9v zener would dissipate quite a bit more heat when run at 18v too
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Post by coldcraft »

it could probably use input and output buffers.
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Post by grrrunge »

Perhaps there's a base here for developing a FSB-modded version of the Pareidolia. The XR-2206 is able to output squarewaves, ramps etc as shown on this excerpt from the application notes :) I'm gonna try this at some point! :D
XR-2206 test circuit
XR-2206 test circuit
XR2206V1.PDF
XR-2206 datasheet
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Post by Jarno »

And, the 2206 can do some pretty weird shapes by skewing the basic shapes. Have a look at Thomas Henry's XR VCO (diy synths).
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Post by LaceSensor »

Looking forward to this, rock or FSB improved if the demos are anything to go by...

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Post by LaceSensor »

LaceSensor wrote:Looking forward to this, rock or FSB improved if the demos are anything to go by...
god knows what my ipad was typing there... :S

any news on a layout / trace?

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Post by roseblood11 »

LaceSensor wrote:any news on a layout / trace?
If someone (you?) draws a clear schematic, I'll draw a veroboard layout.

But maybe a pcb layout would fit in a 1590B enclosure...

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