EHX - Micro Synth XO Version  [schematic]

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Re: Micro Synth XO Version EHX (half-schematic)

Postby zmix » 03 Jul 2018, 13:53

ecollins12 wrote:OK, I have figured it out. Thanks to reading the Stomboxology article. This is for the xo version...The transistor is basically a switch. The clean guitar is on the emitter. When turned on via the divided square wave, only half of the AC signal is passed. Kind of like a /2 sine wave. The jfet just buffers the signal which is then filter a bit by the 220nF cap. I was thrown off because the schematic has the sognal from the Jfet tied to square wave from the 4013, which i believe is NOT correct.


This is fascinating. I have been a fan of the microsynth since it's introduction but never owned one until now, a second hand "XO" version I got yesterday.
I have been completely mystified by the sound of the sub octave circuit. It actually seems to reproduce the tone of the input signal (i.e. pickup selection, etc) and even more bizarre, fret noises when sliding up or down the neck of the guitar. I've never heard anything like it that wasn't a DSP based "Harmonizer™" based pitch shifter, and certainly never thought this sound would come from a basic divider circuit.. it's really something else!

People describe the differences between the original versions and the XO in the sub octave, describing the original as more 'synth like" -- which is what you'd expect from the square wave derived output from a 4013 flip-flop. I'll take a look at the schematics here and elsewhere, but it's quite possible that the original input signal is being chopped by the divider output and added to the square wave.
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Re: Micro Synth XO Version EHX (half-schematic)

Postby P-Trash » 05 Jul 2018, 12:59

zmix wrote:This is fascinating. I have been a fan of the microsynth since it's introduction but never owned one until now, a second hand "XO" version I got yesterday.
I have been completely mystified by the sound of the sub octave circuit. It actually seems to reproduce the tone of the input signal (i.e. pickup selection, etc) and even more bizarre, fret noises when sliding up or down the neck of the guitar. I've never heard anything like it that wasn't a DSP based "Harmonizer™" based pitch shifter, and certainly never thought this sound would come from a basic divider circuit.. it's really something else!

People describe the differences between the original versions and the XO in the sub octave, describing the original as more 'synth like" -- which is what you'd expect from the square wave derived output from a 4013 flip-flop. I'll take a look at the schematics here and elsewhere, but it's quite possible that the original input signal is being chopped by the divider output and added to the square wave.


Hi, zmix :) Maybe you can make a couple images of your microsynth's pcb ? I think, it may help to look for errors in the scheme or in the finished layout. Especially interesting to look at a supply part
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Re: Micro Synth XO Version EHX (half-schematic)

Postby zmix » 10 Jul 2018, 21:01

P-Trash wrote:
zmix wrote:This is fascinating. I have been a fan of the microsynth since it's introduction but never owned one until now, a second hand "XO" version I got yesterday.
I have been completely mystified by the sound of the sub octave circuit. It actually seems to reproduce the tone of the input signal (i.e. pickup selection, etc) and even more bizarre, fret noises when sliding up or down the neck of the guitar. I've never heard anything like it that wasn't a DSP based "Harmonizer™" based pitch shifter, and certainly never thought this sound would come from a basic divider circuit.. it's really something else!

People describe the differences between the original versions and the XO in the sub octave, describing the original as more 'synth like" -- which is what you'd expect from the square wave derived output from a 4013 flip-flop. I'll take a look at the schematics here and elsewhere, but it's quite possible that the original input signal is being chopped by the divider output and added to the square wave.


Hi, zmix :) Maybe you can make a couple images of your microsynth's pcb ? I think, it may help to look for errors in the scheme or in the finished layout. Especially interesting to look at a supply part


Image
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P-Trash (13 Jul 2018, 10:52)
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Re: EHX - Micro Synth XO Version

Postby zmix » 11 Jul 2018, 13:37

Apparently I'm unable to edit my posts? Just right click that image to download and view the whole thing.. hope it helps..!!

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Re: EHX - Micro Synth XO Version

Postby P-Trash » 13 Jul 2018, 10:54

zmix wrote:Apparently I'm unable to edit my posts? Just right click that image to download and view the whole thing.. hope it helps..!!


zmix, you are amazing :applause: thank you!
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Re: EHX - Micro Synth XO Version

Postby zmix » 17 Jul 2018, 01:52

I'm contemplating modding my Micro synth into a "Bass" micro synth because it won't trigger on any pitch below an "A" when using an octave divider before it,.
The changes listed in the schematic appear to alter the LP filter cutoff from 47Hz to 20Hz, but more importantly R24, when changed from 2k2 to 4k7 drops the HP frequency of R24/C7 from 72Hz to 33 Hz

NOTE THAT SOME OF THE PART NUMBERS IN THE SCHEMATIC HERE DO NOT CORRESPOND TO THE PART NUMBERS OF THE XO PEDAL ITSELF

R24 / C7 in the schematic are labeled as "R61" and "C55"

I'm going to simply tack solder another 1µf across C7 to drop the frequency to 36Hz and see how that goes:

Screen Shot 2018-07-16 at 20.49.28.jpg
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Re: EHX - Micro Synth XO Version

Postby KevinMitchell » 17 Jul 2018, 15:31

My layout will show the variations for guitar and bass :roll:
Sorry guys I've had allot going on. Some bad and some very good. But all is well.

I'm still picking away at this. Soon I'll be completely satisfied and will put up some samples along with the toner transfer layout. Might be a while before I have boards manufactured for distribution.

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Re: EHX - Micro Synth XO Version

Postby P-Trash » 03 Aug 2018, 13:30

Hi. Maybe someone may help me. Is it right to connect all pins#4 to v- and pins#8 to v+ (I talk about 4558 and 2272)? And should I connect 13700 pins#6 to v-? (Seems like pins#11 goes to v+, hope at least that is right)
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Re: EHX - Micro Synth XO Version

Postby Nocentelli » 03 Aug 2018, 15:42

P-Trash wrote:Hi. Maybe someone may help me. Is it right to connect all pins#4 to v- and pins#8 to v+ (I talk about 4558 and 2272)? And should I connect 13700 pins#6 to v-? (Seems like pins#11 goes to v+, hope at least that is right)


Yes, you are correct.
brownwhopping wrote:How can I learn by reading threads an making circuits, when some day I can see a lawsuit or somebody beat me in the face for that?

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