Thursday, September 22, 2011

6V Gakken-based Filter Sounds

This is a demo of the Gakken-based 6V filter I made last year. Had this in my multi-tracker since then, but CD drive broke on it, so could not export any audio until now.
This is a B-line with squelchy fills in between. The original sounds were made on the Korg EMX-1, and each was fed individually through the filter at different settings.

It really is an easy build, and even though its not great to tweak, it does work nice via CV modulation (?), and it doubles as a lo-fi distortion box.
I have also fed drum loops thruogh it, and with some gating they sound pretty sick.

This is a copyright free demo, so if you like the sounds feel free to sample the crap out of 'em! Just stick a link in a comment so I can hear what you did with it.

HOMEMADE no drums by MickeyBoyeeee

Wednesday, May 18, 2011

Monotron-Squared - Demo

Here's another jam session to demonstrate the sounds of the Monotron-Squared, a dual VCO monotron with square wave circuit - see earlier posts for project development.
Monotron-Squared - Jam/Demo by MickeyBoyeeee

Tuesday, May 17, 2011

Monotron-Squared: Preliminary Demo

Here's the first demo of monotron-squared, which is very close to being complete and tempting to keep playing in its current (not-quite-finished) state!
Note that the square wave-shape circuit is engaged, and the only pots I use hear are cutoff, resonance, LFO rate, LFO depth, PWM, keyboard tracking depth, and the pitch range (1Meg-ohm) that drives the second VCO from the first (see previous posts).
Also, the 1Meg pot is not grounded (case wise), so I only touch it for some buzzy interference effect...
More to come.

Saturday, May 7, 2011

Monotron-Squared update

1 mega-ohm still not enough! Though much better. May do a voltage divider before pot.
Also, can't get CV mixer to work, so will either build MFOS mixer (which I have for audio out from mono 1 and VCF2  (as separate filter input) OR I may just get an RC4580, as this op-amp operates at 5V no problem. Getting some fat sounds out of it so far - will put some demos up soon.

Friday, May 6, 2011

Monotron-Squared update

Wrong about 300k ohm on CV link between VCOs - took out resistor to reinstate pot as 500k, and I think I'll change it for a 1Meg pot!!
Also, from Din Sync's CV mixer design, 100k resistors on inputs (from VCOs) are too big - tried parallel connection with 100k to give 50k, and had much stronger signal. In fact, with the 100k's, the square wave mod does not work - so will try 47k (or even 36k or 25k?!?!).
Also, the polarizing switch was busted, so testing became frustrating. Have to re-do switch!
When polarizing mixer is working, its amazing!
(Note: LM358 was working, but I did try 5532 and it does not like minimum supply voltages!)

Lesson: Get a solderless breadboard, mate!

Sunday, May 1, 2011

Monotron-Squared - problems update

Dual Oscillator Problem Fix:
So I found a way to fix the dual oscillator connection, and combined with a 260k potentiometer, will also adjust the range of the second VCO. This should work in a similar fashion to the range adjustment for the monotrons' ribbon "keyboard", except it'll be adjusting the range of the incoming CV signal.

The connections I am using are C5 of monotron 1 (there is no capacitor here, just the terminals, and labeled NU on the schematic from Korg), and the middle bottom pin of Q1 from monotron 2 (which I think is pin 2, but could be pin 4 - have no data sheets on that dual transistor - don't know which way is up on it either!).
Between these connections I put said potentiometer - only had 500k, so added a 550k in parallel to make it about 260k - anything less than 100k has a really widely spread range, and more then 300k is also useless. Still, this will be neat for adding layers of notes.

The pitch knob is still operational on second VCO (monotron 2), but the most exciting thing is that any pitch bending on VCO 1 (i.e., from the LFO, or CV pitch bend) is also received at VCO2!!

CV Mixer Section:
Since I'm still a bit crap at soldering, I often file the gaps between the copper strips on the pre-fab experiment boards to make sure there are no shorts. Since I disconnected and reconnected a few times, I had filed kind of sloppily and had actually divided one of the power rails!! What a doughnut! So I reconnected this using a blob of solder.
Now, when things were not working properly, I still had the polarizing CV mixer section working, but since filing the power rail I also dropped the LM358 op-amp on the floor! I still have not hooked it up again and may need a replacement. I do have a NE5532, but its minimum supply voltage is +/- 5V. The monotrons' Vcc is 5V, but I have measured only 4.67V and have concerns about this operating inefficiently. Therefore I'll probably just replace the LM358 if need be.

LFO Routing:
I have since stripped down most of my re-route switches for LFO 2 (LFO from monotron 2) but have a short between the switches I re-did. I used the soldering iron to shrink the heat shrink, and I got a little solder in this, so I think it'll be an easy fix.

VCO 2 Routing:
Since I'm re-doing so much, I decided to try and flip the output of VCO 2 from before the square wave voicing circuit and after it, so that in the former connectivity the dual sawtooth waveform will get some square shaping, and the latter connection will combine square and sawtooth waves. Also, I have a connection to take VCO 2 directly back to VCF 2 - which is then equivalent to simply mixing two individual monotrons - each being played from the same CV notes.
This should give some really fat tones and harmonics - in fact, with the triggered noise gate output, mixing VCF 2 out put with VCO1, with some LFO and stuff, and lots of resonance, I'm already getting some dark and twisted overtones layering up the single voice. Its pretty awesome.

So, all I have to do is wire/solder CV 260k pot between monotrons; re-do CV mixer inputs and output; check LM358 op-amp is working - if not: replace it; clean up or fix LFO routing switches; and, drill out one more hole in the front panel to accommodate 260k pot.

In the future I may try to reinstate the ribbon controller, as its quite fun to use, and great for wobbly effects and sweeps, etc. But to do this I need to get hold of a ribbon cable connector - I already have an adequate piece of ribbon cable that I stripped out of a busted DVD player, and it is compatible with the monotron ribbon cable connector. But not sure if I can be bothered just yet...

Wednesday, April 6, 2011

Monotron^2 - Troubles

So, my LFO routing was not quite right - added unnecessary diodes in wires and actually prevented signal from leaving LFO section!
VCO 2 does not work - this is the monotron unit that I first modded - so may have damaged something via over heating! (I get 3.5V instead of 4.58V - as with VCO1 from newer unit!)
Other issues: CV (pitch) input voltage gets divided, so can only control one unit at a time from a single CV line - can't just put them in parallel (I don't know why????) else you have to play notes way up the keyboard. So will try to link units via a different connection point!
I am getting a strong gate signal across both units, and it is re-triggering both LFO's perfectly.
The audio out mixer works a charm (nice and clean too - all noise does come from monotrons).
Also, square wave mod works nice, as does the PWM and the noise gate circuits.
Finally, using the second monotron's filter section for a separate filter also works great, but I do have to put an input resistor on it, as it totally distorts right now. The aux in has 10k resistors on each channel, and I found that this distorts with a hot signal, so I'll probably put 15k or 20k instead - mono, of course.
I have not determined if the CV mixer is working yet, but it seemed to with one channel. And I also got the polarization going on the one working VCO, and it does do some sort of voltage inversion - very cool.

Had a short on CV mixer across output and supply - now fixed.

Should have used stranded cable for VCF connection from Monotron++ board, as it keeps breaking while I trouble shoot.

Sound checks in the studio.
Almost there - sounds fat with single VCO...
Get some fat tones with the one VCO and square wave mod, and since the gated output comes from the audio mixer, can get some added resonance from the second filter without any aux input!
Still, it will be even fatter with dual VCO...
Will update very soon with trouble shooting and repairs.

Monotron^2: Coming Together part 2

Without testing - just too excited about getting the thing working!

Thursday, March 31, 2011

Thursday, March 17, 2011

Monotron-Squared Continues...

Got all the parts now, and all the boards are prepped. Just wiring up the pots and switches, and figuring out how to mount all the different parts in the enclosure. Also have to cut some traces and solder onto both monotron boards - mono 1 and mono 2 - in order to have dual VCO. May not be able to have SYNC option for the two oscillators, but will try anyways.
Also, using VCF 2 (filter of mono 2) as a stand alone filter, with its own line out.
Altogether will have dual VCO with in-built CV mixer to mix them, squarewave VCO waveshaper with PWM, a dedicated filter, and an audio out mixer to mix the mono 1&2 and the VCF 2 outputs.
To do all this, I utilized a voltage inverter to get +/- 5V supply voltages for the CV mixer circuit and the audio mixer circuit. The CV mixer was modelled from Din Sync's module(, with different Op-Amp and smaller supply, and the Audio mix out circuit was taken from the "simple mono mixer" at MFOS (
Anyway, still got tons of work to do - but should be done soon!

Here's the Square Wave & PWM board with all components installed. This circuit board includes a gated output.
Here's the votlage inverter and CV mixer circuits.
Same board as above, but with added Audio mixer circuit.

Board mounts for some switches and another board for the PWM pot, Square/Saw select switch, and polarizing switch for CV mixer; both were manufactured via chemical etching.

Where they'll sit in enclosure.
  Had alot of trouble trying to get matching knobs - so used regular potentiometers and knarled them myself!

Knarling me Knobs!

Looks more like monotron style knob.

Next to monotron knobs.

What they'll look like in the box.
Mounts for the filter knobs.
Mounts for the VCO mixing pots.
All the Op-Amps, and a spare 5532.

Thursday, March 10, 2011

Monotron mkII Enclosure - drilled and ready

Got the box!
Waiting for one more Op-Amp to arrive in the post, and got to pick up some knobs, some more chemicals for board mount switches (cheap ebay switches - don't match breadboard grids!!), and a new soldering iron with a fine tip (in order to make connections on device side of monotron pcb's).
What a mess!

Thursday, February 10, 2011

Another old tune from the dusty storage room: Wideload

Another older tune - not quite polished enough to release, but it has a couple of fat moments in it.
Again, made as Prysmal - before Fulcrum EP was made.
(This is an mp3 also, but still has a few uploading glitches in first minute!)
Wideload by MickeyBoyeeee

Wednesday, February 9, 2011

4 unreleased tracks: Fulcrum EP

Here's some tunes I finished a few years ago - artist name Prysmal. Uploading on soundcloud caused some glitches around hihats on intros - I'll try and reupload soon. I intended to release an EP of these 4 tunes:
(Note: Re-uploaded on Soundcloud as mp3's rather than .wav's, and only Fulcrum and Pingpong has some glitches on hihats on intro - I've uploaded them about 6 times now!)
1. Fulcrum
Fulcrum: Track 1 from Fulcrum EP by MickeyBoyeeee
Pingpong: Track 2 from Fulcrum EP by MickeyBoyeeee
Unstable: Track 3 from Fulcrum EP by MickeyBoyeeee
4.Bradley's Song
Bradley's Song: Track 4 from Fulcrum EP by MickeyBoyeeee

Tuesday, February 1, 2011

Square Wave & PWM Board - Nearly Done

Here's the board with most of the components added.
Just waiting for some PCB mount switches and a 2SC2878 transistor to arrive in the post, and have to find some monotron-like knobs - PCB mount type.

Design from Takeda's Monotron++ at
Also in the process of finding out if a NE5532 can substitute a 4580 op amp. It seems that some people think a 5532 will only operate properly at over 9V, and requires +/-V supply. The 4580 can run as low as 3V, so 5V Vcc will work. The 5532 is rated as low as 2V (in spec sheet) but may require +/-V supply.
This should be OK as I've made another circuit to "mix" the VCO outputs from 2 monotrons (more on this later...) for which I had to get -5V for an LM358 op amp to run properly. It seems most people go for a +/-12V supply for such op amps, but that is just from uneducated and uninformed research (i.e., on the web). Again, this chip is rated quite low, so hopefully it'll make it with +/-5V supply.
I'm getting -5V from an ICL7660, which I think replaces (or is identical to) the MAX1044. By hooking up some capacitors and grounds, you can invert your supply voltage. The circuits I found (which were identical) worked for both 9V and 5V supplies. In fact, the circuit (which I'll post later) states on the schematic that it is good for 3.5V to 10V; that is, you can get -3.5V to -10V from a positive supply.
More progress reports to follow.

Tuesday, January 25, 2011

Monotron Modifications Continue...

Prototype board manufactured!
Design for board from here:
Now, since I drilled, pressed on the etch resist and finally etched out the circuit board using some chemicals, an updated design was posted. I'm still going ahead with the old design.
Square wave, PWM, noise gate, clean audio out board

Etching off the copper...


Transparent view - all holes drilled.
  Components to follow... I still need to get some board mount knobs that match the monotron knobs (suggestions welcome) - I already stripped a monotron (to use as second VCO) and used three of the knobs on remote board (see earlier post), but don't want to buy a 3rd monotron just for knobs - plus they're not that easy to remove (when your green like me!).
The extra knob-mount point (to right side of board in last pic) is intended for "glide" control in conjunction with the midi mod on monotron++. I'm not doing the midi upgrade, so instead I'm going to mount a keyboard tracking depth knob (as I did with the Gakken) since its a bit more versatile than just a keyboard tracking switch at a fixed resistance; will probably put switch too.

Thursday, January 6, 2011

Monotron - Remote Knobs for VCO&LFO2 and Stripped Monotron

Here's the remote board to hold the knobs. The middle was going to be the clear LFO rate knob, but I broke it in the process of trying to recreate LED and attaching it with super glue. Well actually it was when I filed the underside to get rid of excess glue and messed up the central pivot (axis pole), and now the wiper jogs off the resistive tracks inside! So I'll have to do a surface mount LED for LFO2 rate.

Remote knob board
 I sat the knobs higher to give space for switches.

Here's the stripped monotron:
Stripped out power supply, jacks, vol. wheel, and knobs
Tried to photograph all the circuitry to create a map - to match up Korg's schematic, but camera is a bit crap:

Wednesday, January 5, 2011

Internal Voltage Divider Done - now get 1V/Oct

Here's a solution to get 1V/Oct - I just used a trimmer as a variable voltage divider to replace the external test V-divider I made before. I'm still tuning it right now, and the sweet spot drives the octave range up two full octaves (So note C3 = C5).

More spaghetti!

So (for novices like myself) I took CV in to pin 1 (could have gone to pin 3, opposite operation), the line the R7-south off pin 2 (the wiper) and a wire to ground from pin 3 (could have used pin 1, opposite operation).
Still, could have saved all the trouble with Silent Way!

Febuary 6th 2011 - Additional Info:
Here's the basic circuit for the voltage divider:

Instead of using two resistors for a fixed voltage divider, a single trim pot replaces both.
Then terminal 1 (or terminal 3) is equivalent to the Vin connection above. This will be the CV input.
Then terminal 3 (or terminal 1) goes to ground.
Then terminal 2 on the potentiometer (trim pot), which is the "wiper" terminal, is Vout above. This will go to south side of R7 if you did Din Sync's mod for CV input.
The interchanging of terminals 1 and 3 does not matter; the direction of operation will just be opposite for either choice - resulting in Clockwise (CW) operation or Counter-CW operation.
This circuit is based on the ratio of Z1 and Z2 (or R1 and R2 for resistors). Because of this, using two 10k resistors is identical to using two 100k or two 1M resistors, according to the following equation:

Vout = [R2/(R1+R2)]Vin
For the list of values above you will always get that Vout = (0.5)Vin.
With a trim pot you can "tune-in" the right ratio to get Gakken on 1V/Oct.

Note that this is the simplest case. To get proper V-division, you would have to know about the impedences of the circuitry connected to it.

Etched PCB for monotron - remote knobs

Here's some pic's of chemical etching in progress. I wanted to keep original knobs from a second monotron - to build a dual VCO monotron using two monotrons - so had to make remote board for surface mount knobs.

Etching off the copper

After a few minutes agitating the board

Was taking longer than expected, apparently chemical reacted with tin coating on paint tray...
Thats why it was getting warm!

New tray - ceramic baby

Almost done - and no skin burned off.

Only the etch-resist remains.

Nice. Rough, but it works.

All of this was also a test run for the squarewave/PWM mod, similar to the Gakken mod, except that the monotron one I found requires a PCB. I've been drilling holes (with a hand drill) and rubbing on etch-resist dots for a while now:

Lots of dots..................

Will put up links and such as project progresses. Next I have to paste on the lines.
So far I've stripped all knobs and jacks off of the second monotron and today I ripped apart the power supply, as I want to feed everything from first unit (if it works???).