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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.

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

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

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

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 thank you!

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:

My layout will show the variations for guitar and bass
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.

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)

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.

PCBs should be available Spring of this year.
Be back soon with a prototype.

-KM

KevinMitchell wrote:PCBs should be available Spring of this year.
Be back soon with a prototype.

-KM

That's a good news))

By the way, seems like exist several revisions of the original pcb, and in newer vertions (like REV. E in Zmix's attachment) V- connected with the case. Because of that, there are some differences between schematic and PCB image. Maybe someone knows, how to supplement the circuit to connect jack's sleeve pin with V-?

Hey guys, any updates? I sprung for a shotgunn modified bass microsynth recently and im in love. I would love to have a diy one to play with.

Due to my morality and EH's sue-happy nature I plan on providing PCBs and OTAs for a clone of the older version I'm calling the Retro Synth. That along with a couple other projects will be released later this year.

The newer version is still in my horizon. Just not perusing it while I have sources for the CA3094 chips. Also - there's talk of companies like CoolAudio or Alfa bringing these chips back into the wild.

-KM

KevinMitchell wrote: ↑29 May 2020, 19:27 Due to my morality and EH's sue-happy nature I plan on providing PCBs and OTAs for a clone of the older version I'm calling the Retro Synth. That along with a couple other projects will be released later this year.

The newer version is still in my horizon. Just not perusing it while I have sources for the CA3094 chips. Also - there's talk of companies like CoolAudio or Alfa bringing these chips back into the wild.

-KM

I'd implore you to reconsider, waste of (a lot of) a rare chip useful for repairs and makes it more difficult for many to build. All of them bar one in the original can be replaced with LM13700 easily and be functionally identical. Several of them in the circuit aren't even using the output buffer that makes the CA3094 special.

Also, I've not heard of any reproductions on the horizon, nor do we know even if they are if they'll be in DIP format still.

After a conversation with Scruffie I've decided that I will peruse the old version - converted to use LM13700 in a 1590BB.

See ya later!
-KM

A reworked Space Drum circuit using LM13700 was posted a while back which might give some clues.

viewtopic.php?t=11251

KevinMitchell wrote: ↑12 Jun 2020, 16:15 After a conversation with Scruffie I've decided that I will peruse the old version - converted to use LM13700 in a 1590BB.

See ya later!
-KM

peruse or pursue ?

Would there be room for the slider pots?

yeah, the slider pots are on a separate board. I believe Kevin said he may do a normal pot board version as well.

I am really looking forward to this.

I had emailed Kevin and am hoping to hear back on his thoughts with the mod info I found.

Basically, the guy who runs FX doctor literally told me he wont mod my pedal (big box version) even for the mods he does offer. the only mod i asked for that he blogged ( on their site) about and posted pics of a modded unit but says he doesn't offer is an effects loop mod. I thought it would be a useful addition. No reason, no explanation other than "the mods listed on our mod page are all we offer".

The other mod is the expression pedal mod for the stop frequency and a "voice" defeat mod.