EHX - Deluxe Octave Multiplexer  [schematic]

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

[img][IMG]https://i1377.photobucket.com/albums/ah50/ege_ergul/EH_Multiplexer_wiring_001_zpsyfeijq69.gif[/img][/img]



Hi, Does anybody know about, what absent resistor values are ? Some of the resistor values are unmentioned on the layout.
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Pote Gui
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Post by Pote Gui »

Hi folks!

I've just finished reverse engineered this pedal as I couldn't find a schematic one the net. It is not as clean as I wanted it to be at the beginning (started this off with a ruler, finished it without...), but it's better than nothing, right? I've planned to make a cleaner one using Kicad when I'll have time, but not for now.
It's on five pages because I couldn't manage to make it with less pages! I think it's quite usable anyway, but you'll tell me. Maybe someone here can make a one-page schematic?
Here we go!
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Deluxe Octave Multiplexer 5.pdf
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Deluxe Octave Multiplexer 4.pdf
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Deluxe Octave Multiplexer 3.pdf
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Deluxe Octave Multiplexer 2.pdf
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Deluxe Octave Multiplexer 1 (2).pdf
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apollomusicservice
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Post by apollomusicservice »

Pote Gui wrote: It's on five pages because I couldn't manage to make it with less pages! I think it's quite usable anyway, but you'll tell me. Maybe someone here can make a one-page schematic?
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Pote Gui
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Post by Pote Gui »

Great! Thanks!

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Pote Gui
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Post by Pote Gui »

And by the way, the (?) near the values are for those for which I'm not sure (hard to see the color and can't measure it unless unsoldered). The revision number of the board is 1325C. So it's a little bit different from the 1325D schematic Dirk posted the link some times ago.

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Pote Gui
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Post by Pote Gui »

Ah, I found some mistakes... I'll correct them and post a new version in pdf.

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uncleboko
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Post by uncleboko »

Page 1 - GE diodes = 1N3666, diode from base of 2n5087 is 1N5226A

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Post by Pote Gui »

uncleboko wrote:Page 1 - GE diodes = 1N3666, diode from base of 2n5087 is 1N5226A
You're right! Thanks for your help. I've checked my drawings and I've corrected them. I'll post them soon.

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toneman
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Post by toneman »

is this the one?
Tone-to-the-Bone

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uncleboko
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Post by uncleboko »

No, it used a CA3098 and was dated Jan/Feb 1978.

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Pote Gui
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Post by Pote Gui »

Ok, I've double-checked all the pages, and now it seems ok. If anyone find a mistake, please tell me and I'll correct them.
If appolo can assemble these five pages in one, that could be nice.
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Deluxe Octave Multiplexer 5.pdf
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Deluxe Octave Multiplexer 4.pdf
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Deluxe Octave Multiplexer 3.pdf
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Deluxe Octave Multiplexer 2.pdf
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Deluxe Octave Multiplexer 1.pdf
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Pote Gui
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Post by Pote Gui »

Hello,

I've recently bought a DOM and it seems that it may doesn't work properly. It does generates one octave down, but fails to generate a clean two octaves down sound.
The other thing that's bugging me is that wether I use the one or two octave generator using the Mix knob, the tracking of the fundamental isn't very good, and the sound jump from an octave down to an octave up and back again to the octave down, etc... in an random way. Plus, there is a kind of delay before the sub note appears after hitting the guitar cord.
Finally, there is a loss of signal between direct and processed sound.
Fuzz is ok.

The schematic is here.

I've checked the power supply and it's ok : +5V/-5V.
The FETs seems ok and the 2N5087 too.
All ICs seem ok.
Pots responds well as expected.

The 4013 is generating +5V to -5V square wave oscillation related to the signal frequency. One output of the 4013 is twice the frequency of the other, as it should be. It works well on the bench with a sine wave at the input, but fails when using a guitar. I can see with my oscilloscope and a guitar plugged in the pedal that the square wave does jump from a frequency up to its double from time to time, which is never the case with a signal coming from a LFG. I guess that's because a guitar generates some natural harmonics that tends to be tracked by the circuit. That's why I think there is a problem with the part of the circuit that extracts the fundamental and stick to it. But I don't understand how this part of the circuit works (page2)...

Another thing I don't understand but doesn't seem to be related to the problem, is that there is almost no DC voltage at pin 1 and 7 of the CA3098 when those pins are the high and low ref at which it triggers. But it triggers... Althought the duty cycle is not really good, it doesn't seem to worry the 4013 that generates perfect square waves at pins 2/5 and 9/12. The trimpot seems to help correct the duty cycle but with the mismatch of the hi and low cycle, it can't help it. I've tried to input a stronger sinewave at pin 8 of the CA3098, and it does improve the duty cycle of the square wave at pin 3 in a way that I can use the trimpot to make it 50/50. So maybe the compressor circuit at page 1 doesn't provide a strong enough signal to allow the pedal to work at its best?

Thanks for your help and advices!

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Pote Gui
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Post by Pote Gui »

Nobody? No idea? No nothing?

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Dirk_Hendrik
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Post by Dirk_Hendrik »

very minimal response then.
Have you attempted to play single notes? These flipflop divider type octavers cannot handle chords. In such a case if it does get enough of a single frequency to operate (somewhat) I can very well imaging the tracking is too poor to effectively do another octave down.

The 4013 based divider will not do octaves up.
Sorry. Plain out of planes.

http://www.dirk-hendrik.com

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Pote Gui
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Post by Pote Gui »

Thanks for your reply Dirk! By the way, it's funny to see the slight differences between the two versions according to our schematics!
Well, even with single notes, the problem remains... When I say octave up, it is relative to the generated octave down, so actually it's the frequency of the original note!

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Post by GBlekas »

I know it’s years later but did you ever sort out that sub divider knob issue?

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