Saturday, February 12, 2011

Monotron Acid Demo!

Korg MonoTron Analogue Ribbon Synthesizer on zZounds

Threw this together this afternoon!

Monotron acid demo by Gravitronic

What you are listening to is two tracks of korg monotron, and some 909 drums via the excellent d16 909 emulation VST.

The first monotron track is MIDI sequenced from ableton live sent to a MIDI->CV converter and finally to the monotron, which has been modded and calibrated to approximately 1V/oct tuning. This is a 24-bar loop that is repeated a few times. There is reverb on this track to give it that acidy depth.

The second track is the 909 bass drum being sent through the monotron, and at the same time me playing the knobs on the front of the monotron for the second synth part. I can't get the monotron gate to open for the external input without playing the oscillator as well yet so I sort of needed to have that second synth part in there whether I wanted it or not.

I had to up to compress the audio and add quite a bit of gain in order to get this loud enough to post but other than that and the reverb this is pretty much raw. No work was done to try to reduce the noise floor, which after 2 tracks combined you really can hear it quite loud. Apparently changing the filter chip will reduce the hiss. Not sure if I'm going to do that or just leave it as it is.. its raw.

Mods to the monotron are as described in a previous blog post.

Korg MonoTron Analogue Ribbon Synthesizer on zZounds

Friday, February 11, 2011

Holy crap I want a octatrack

Second video is super loud, so be careful.

Makes me want to sell my mopho keys and play with this & my DIY rig and get away from ableton live.

Tuesday, February 8, 2011

Starting out with DIY

I was recently asked on the vintage synth forum about beginning DIY. This seems to come up a lot with synth players who might be looking at DIY to save money, out of interest for a specific DIY synth, or as another hobby they are interested in learning.

A lot of people will tell you DIY synth building will not save you money. That is a half-truth. DIY gives you endless options of how you want to build your project. If you care about perfect panels and pay for professionally cut panels, then you will probably not save money. If you plan ahead and buy parts for a few things at once, you can save a lot. With the TM3030's I'm building now, I am building two (which is a negligible addition in time when you consider part sourcing and label planning) and have sold one to an interested friend. After selling one my total cost on the other TM3030 will be approximately $100. For a 303 clone!

Anyways here's my response in full about synth building:


DIY is awesome! I'm about to start a DIY modular after building a few synth kits and if you're smart about it you definitely get to save money and if you're like me, building stuff is enjoyable.

I did have a paia fatman, however I did not build it myself. That synth I bought already built from a guy selling off his stuff for cheap. However I did recase the rackmount unit into the desktop enclosure so I got to look at it a bit. As well, I've built.. a midibox SID, MFOS soundlab, x0xb0x, and am now finishing two Oakley TM3030s (basically a 303 clone without the sequencer).

The first synth I built was a MIDIBOX SID and I must say at first I had no clue what I was doing. Amazingly, I got it all working. I would suggest maybe a sammich SID as a first project. You get everything you need as a kit, the community is great, and it's not that complicated of a build whatsoever. Stuff the parts, fit it in the case, tada it's done. It looks like the struthi-1 is also a kit that contains everything, which would make it a good starting synth. However I think it's sold out a lot of the time.

I'd say the PAIA would make an excellent "second synth" project. Mainly because if it didn't work after putting it together without some idea of what's going on, you are going to be stuck without someone who has an oscilloscope and an idea of what's going on.

As for soldering skills, I'd suggest spending 50-100$ on an iron with an adjustable temperature, and also learning the proper technique from watching some videos online. The key thing that I got wrong for a LONG time was that you need to apply the iron tip & solder directly to the components you want to solder. You cannot put solder on the soldering iron tip, then apply the tip to the component, and live with a touch of solder holding the things together. That will not last at all!

If you are serious about learning and don't want to wreck your first synth I'd suggest maybe getting a little kit from sparkfun or the MAKE online store to start. It'd be a good warmup and as a small project you wouldn't get over your head.

After doing a couple full kits and getting the soldering skills down, the next big skill to learn is how to source components from online stores. A lot of projects just sell you the board and a list of components and you need to learn to source them yourself from mouser, digikey, etc. I did the x0xb0x like this (self-sourced the components) but thankfully started with someone else's bill of materials (BOM). This was a good initiation to filtering out the available parts you don't care about and finding the ones that fit your board. The DIY forums on,, and, are great resources full of people to guide you when you go wrong.

The other step that's separate from soldering is case building. I wasn't very good at this at first but I've made a technique that is cheap and passably good enough. Basically I make my frontpanels and drill guide as an image in Inkscape, print them with a normal laser printer, then use gloss as both the glue to glue the image onto whatever case I'm working on, and then also coat the image with a healthy layer of gloss as a sealant. The result is a bit sparse but is good enough. Especially since it costs ~$1.00 instead of $50+ for a professionally cut frontpanel.

You can see some of my work on the Oakley TM3030s on my blog here: ... pdate.html . It has some pictures of the labelling process I was talking about. I will probably also post this Q and response on my blog as it's a full summary of my opinion on starting on DIY. Good luck! Let me know how it goes and if you get stuck I'll try to help.



Sunday, February 6, 2011

Modded Korg Monotron

Buy a Korg MonoTron Analogue Ribbon Synthesizer on zZounds

This is my work in progress modified Korg Monotron.

So far I have the pitch/filter CV and gate wired up, still have to do audio in/out and make the power supply as mentioned by the DIN-Sync blog.

To fix the pitch CV tracking issue thus far I have removed resistor R11 as described along with tons of other information on Steve Woodward's blog.

For the audio output I plan on using the pre-amp output which will hopefully be less noisy than the headphone out! This is described in an Unofficial Monotron Forum thread.

As well as adding input/output I plan on fixing the "click" at the end of the notes as described by Scott Willingham in a Muffwiggler forum post.

Unfortunately I'm dealing with an issue other people haven't mentioned much which is that the synth seems to pick up my hand's proximity and it effects pitch and filter cutoff frequency quite a bit. Makes it hard to tweak, although you can "play" it a bit just by waving your hand! I'd like to fix this but am not sure where to start... I read somewhere that someone tried wrapping it with aluminum tape to protect, I might try that as I have some from an xbox360 RROD fixing attempt.

Buy a Korg MonoTron Analogue Ribbon Synthesizer on zZounds

Tuesday, February 1, 2011

TM3030 Update!


Did the logos/cases for the 2 TM3030s and also the Korg Monotron breakout box :D. Boards almost finished, need to do big caps, rare parts, and wait on 1 "new" rare part shipped from hong kong. Should have everything else finished by it's arrival.


I do the frontpanels with the cheapest method known to man. I make the labels with Inkscape, print them with a laser printer, cut them to size, and use "Polymer Medium (Gloss)" as both the glue and coating to protect the label. Use a paintbrush and cover both the back of the logo and the top of the case, not too thick. Then lightly press the paper to remove any bubbles and let excess gloss exit sides and be removed.

Let it dry a bit before applying the top coat. Your paper may be transparent a bit while the gloss underneath is drying and the results look like they'll be terrible but when it dries the paper becomes opaque again. Note: when pushing out bubbles or extra gloss do not press too hard or you will make a blemish. Look at the monotron breakout box for what I mean, the dark spot is where I used a ruler to press the paper down to remove the bubble. Don't do that, just gently use your fingers.

Coat well on top to protect and seal the logo.

After it's dry, you can drill out the holes. Be careful while drilling, sometimes the logo will rip a bit. As long as it's not much it'll be covered by the knob or jack anyways.

It's not pro but I can do labels for pennies this way and the result is pretty nice. If you used a thicker stock paper you'd probably get better results.