OKKO Dominator  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
euronymous0001
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Post by euronymous0001 »

i spot some mistakes on the component labels
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Saruman
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Post by Saruman »

С3 - 6n8
R18 - 47K
R16 - 10K
R17 - 47K
R19 - 47K
R20 - 39K
C11 - 220n
C12 - 51n
C13 - 2n2
C14 - 10n
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tb.JPG

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Post by Saruman »

R10 - 22K
R13 - 1K
C7 - 220n !!!

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mundry
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Post by mundry »

Hello everyone and sorry for my bad English.
On our forum we have been following this interesting discussion and we design a layout on a single-side with only 4 bridges, it uses a TLC2272 instead of two TL072.
Plus I think it is much more versatile replace the switch for the mid range with a potentiometer. If I understand how it works should be an on / off / on that parallels the 1M resistor with the other two to be precise cuts;it could be replaced with a 1M potentiometer with a 10k resistor in series i think.

Last question: what value C6? 100pF 100nF or?

here's the schematic

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and the eagle files

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Post by mundry »

...here's the schematic
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okko mod schematic
okko mod schematic

roseblood11
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Post by roseblood11 »

Thanx for posting, but I can´t see the Image...
Could you please post the layout as GIF and a scaled pnp file?
Not everybody has EAGLE Cad (but this would definitely be a reason to install the freeware version)

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Post by roseblood11 »

Does the voltage supply really work properly? How much voltage do you get out of the 7660S? With 1n400x diodes, it´s not much more than 16V, I guess? Can the 7815 work correctly with that input voltage? The datasheet says: "input voltage required to maintain line regulation: 17,7V) I´d suggest to use schottkys (1n5817 or similar) for D1 and D2...

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Post by Saruman »

the latest version of the schematic:
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OKKO DOMINATOR cir.JPG

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Post by Saruman »

С6 - 100pF

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mundry
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Post by mundry »

here's all the schematics, layouts, master and partlist.
mundry wrote:Hello everyone and sorry for my bad English.
it uses a TLC2272 instead of two TL072.
SOrry,is a TLC2274 insted of two TL072

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Post by Saruman »

mundry, R19 - 47k

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Post by mundry »

my fault , i didn't update this value

here's the projects updates, i can't delete the old files....
Attachments
okko dominatrix.rar
okko dominator with TLC2274 and midrange pot control
(406.77 KiB) Downloaded 779 times
okko dominator.rar
okko dominator with TLC2274
(384.93 KiB) Downloaded 679 times

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Post by audioguy »

mundry wrote:my fault , i didn't update this value

here's the projects updates, i can't delete the old files....
Is it verified?

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Post by roseblood11 »

That schematic shows the tlc2274 again... I wonder if that´s really a good choice here, because its max voltage rating is 16V. If the voltage doubler is build with 1n4004 diodes, it will deliver slightly more than 16V, and even more than 17V if schottky diodes are used.

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Post by guiddruid »

It seems completely pointless to run some of the opamps off the unregulated supply anyway. I would be suprised if it were possible to clip those inputs, given the amount of attenuation following the distortion stage.

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Post by mundry »

i can modify the layout and supply the TLC with Va (15v)

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Post by guiddruid »

Probably better going the other end of R38 - I assume that resistor is there to affect the distortion stage.

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Post by mundry »

here's the latest version 1.2

-i've changed the IC2 supply from Vb to Va so the supply of IC1 and IC2 is the same, i don't understand what kind of problem can introduce R38 :scratch:
guiddruid wrote:Probably better going the other end of R38 - I assume that resistor is there to affect the distortion stage.
-updated the charge pump diodes with schotty type (i'll try it Roseblood)

who had already made pcb with previous old versions can easily replace the TLC2274 with the TL074 without change anything
Attachments
okko dominatrix V1.2.rar
Okko dominatrix latest version
(333.11 KiB) Downloaded 835 times

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Post by roseblood11 »

That´s a little to quick...

Will the 7815 work properly, if it has to deliver that much current? Remember my question from a few days ago:
Can the 7815 work correctly with that input voltage? The datasheet says: "input voltage required to maintain line regulation: 17,7V)
Even with schottkys you won´t get 17,7V out of the 7660S... Maybe the configuration in the original Okko pedal only works, because the 7815 dosn´t have to deliver much current?

Or maybe it´s a part of the sound that the power supply is a bit weak? Someone should measure that under working conditions
(Voltage at the output of the 7660S and the 7815)

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Post by guiddruid »

Standard linear regulators have a dropout voltage (=minimum value of vout-vin) that's around 1.7 at full load - it's a little less at lower output currents, but still over a volt.

The charge pump will output at most (0ma load) 2*(9V - diode drop). With magic diodes and no load you would be at 18v. Take two diode drops off that, and you are at most at 17.4 for schottkys, or 16.8 for ordinary signal diodes. Add any load current, and it's looking dodgy.

roseblood11 is probably correct that the regulator may well start dropping its output below 15V (and therefore letting charge pump noise through) with the tone control opamps connected.

Replacing the standard 15V regulator with an "ultra low dropout" type should sort that - they can go down to about 300mV dropout.

Powering the tone opamps through R38 would mean that any variations in the current drawn in the distortion opamps will be seen on the power rail of the tone opamps. It's possible the current varies quite a bit, when the distortion opamp is distorting. Connect the tone opamps straight to the output of the (LDO) regulator, and you don't have to worry about that.

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