Category Archives: Tech

Custom MIDI Slider box

Time for a new project, inspired by this post on Gearslutz. A custom DIY MIDI controller featuring three full size 100mm sliders and based on a Teensy 3.2. This will be used to control MIDI CC’s for my Kontakt libraries.

I sourced components as close as I could to the original post. The Teensy was from Amazon, the sliders and case from Farnell and I’m just waiting for some black 8mm slider knobs from eBay. Was difficult to find 100mm sliders and a case with the right dimensions in the UK so I’ve posted links below.

Bourns B10k Slide Potentiometer
Takachi Plastic Enclosure 30 x 150 x 100

Cost so far is around £50, but I already had some of the components such as LED, USB connector etc. Still quite reasonable though and I’m surprised something like this doesn’t already exist in the market.

Filter update

After some more thorough testing, I determined that the volume of the 3320 VCF was a little on the quiet side, noticeably lower than my other modules. Putting this down to the use of 100k resistors rather than the 91k specified on the circuit board, I decided to replace them and am happy to report this did the trick!

One other interesting thing I noticed is that even with the resonance turned all the way down, and cut-off all the way up, the 3320 VCF does add a little bit of colour to the incoming signal, softening the edges and (dare I use a cliché) making it sound warmer.

Resonance seems to self-oscillate nicely from about 50% onwards and seems pretty easy to tune. There are also optional solder points on the PCB for a 1v/Oct input, so I’ve no doubt it could be quite a capable oscillator too.

All in all, a great addition to my modular synth and looking forward to trying out some other Guru Gara Synth modules in the future!

Pain in the resistors

Well that was a pain in the… resistors.

Finally got the new 3320 VCF module working after tearing my hair out a little. With the lockdown, I’ve had to source the components in dribs and drabs and can’t always get the exact components stated on the circuit board.

About a week ago, I finally took delivery of the last capacitors I needed then excitedly plugged it in and heard… nothing.

A bit of headscratching later, I chanced upon the idea of sending a voltage through the CV input which initially did nothing, until I swept the filter knob, which revealed a comb filter type noise, but only when the knob was pointing straight up. Resonance did nothing to the sound, and I had silence at either end of the filter range.

Where do I start?

My first thought was that perhaps the 100k B potentiometers were faulty, or that I had bought the wrong ones and got my Linear vs Exponentials in a twist. So, I checked stock at http://www.thonk.com and fortunately they had some.

Then, this morning, I had the joy of desoldering the old pots and installing the (arguably superior) new ones. Unfortunately, it didn’t fix the issue.

I checked my soldering again – all looked sound to me – so as a last resort double checked that I’d used the correct resistors. And low and behold, the 91k resistors I had been sent (and which were in a bag labelled 91k) were actually 910k! In fairness, the difference between the two is just a red stripe rather than an orange one, and even my wife wasn’t sure what colour they were when I asked her to check. So I desoldered all four of them, and replaced with 100k resistors (the closest I could find) and I’m pleased to say the module sprung into life.

I still didn’t have any resonance though, but tracked this down to some damage I’d inadvertently caused on the board around one of the resonance knob pins. I could just about work out where the pin was meant to be going though, so added a jumper wire to link to the appropriate resistor, and I have resonance too!

Whether the 100k vs 91k resistors makes a difference to the sound, I’m not really sure, but it sounds good to me and I’m currently enjoying feeding some sample and hold through the CV input.

This was the first time I’d built a module just from a PCB and Panel, rather than a full kit, and it definitely makes me appreciate the convenience a full kit gives you, even if I did save a bit of money along the way.

Korg DDD-1 LCD

So the good news is the Blue LCD I bought on ebay is fully compatible with the Korg DDD-1! The model I went with is the HD44780, although it has slightly different dimensions to the original, so I had to get a bit creative with attaching it to the case. I also had to extend some of the wires from the circuit board so they could reach the solder points.

Unfortunately, my excitement was short lived as I managed to kill the backlight within a few minutes as the voltage was probably too high.

So, after ordering another replacement (Yellow backlight this time), I decided to put an inline resistor on pin 15 to reduce the voltage. A quick google suggested something around 47 ohm should do the trick, but the smallest resistor I had to hand was 100 ohm.

I’m happy to report it all works fine though, and with no annoying whining sound!

I’ve also replaced the main navigation / cursor buttons which are a lot more responsive now. The back-up battery replacement was a bit fiddly, but I’ve done that too 🙂

Interestingly, the HD44780 was also the model I used on my Akai S2000, but that’s working fine without an inline resistor!

Hello again!

Hello again, it’s been a while! The last 18 months have seen me buy a new house, move in, move out again, then pretty much rebuild it.

We are finally getting back to normality though, and I now have the luxury of a dedicated studio space in the house (no more shed at the end of the garden!).

Whilst unpacking my equipment, I decided it was time to give some TLC to some of my more aged items.

Korg DDD-1 Drum Machine

Korg launched the DDD-1 drum machine in 1986. Built like a tank, it’s sounds have arguably aged better than competitor drum machines of the day such as the Roland TR-505 and Yamaha RX series. You aren’t limited to the 18 onboard sounds either, as it has 4 rom card expansion slots and Korg released a large number of expansions which pop up from time to time on ebay.

It also has an optional sampling board but these are very difficult to find, not to mention cost prohibitive on those rare occasions when one comes up for sale. More usefully though, an enterprising individual has reverse-engineered the rom cards and built an adapter that lets you add your own sounds, stored on EPROM chips.

I have a couple of these adapters myself, and have started burning my own EPROM’s with sounds created on my modular system. Of course, as the DDD-1 is only 8-bit, the samples don’t sound exactly the same as the originals, but this only serves to make them more unique.

Time for surgery

I purchased my DDD-1 a couple of years ago, and it generally works fine, but does have a high-pitched whining noise which I suspect comes from the LCD backlight. This isn’t present on the audio outputs though so is something I’ve largely learned to live with.

More recently though, I’ve noticed that the selection slider is a bit temperamental and the plus and minus selection buttons need quite a hard push before they work, which makes it difficult to program. Being over 30 years old, there’s a high probability the back-up battery will soon fail too, so I’ve decided some surgery is in order.

The back-up battery is your usual CR2032 button affair, although in their wisdom, Korg elected to solder this on the board. So I’ll also be fitting a battery holder to make future maintenance easier.

I’ve also noticed my Akai S2000 display is becoming fainter too, so will probably replace the LCD on that too at the same time.

Simple modular sequencing with Max For Live

Have been working on Max For Live patches to sequence my Drum Skiff.

As I mentioned previously, I’m using an excellent Max For Live Mutable Grids emulation by Mots, along with a CVPal controller patch from Spektro Audio. (Check out their CV Toolkit too!).

This outputs three channels of drum triggers (or gates) through the CV Pal module, all perfectly synced to Ableton Live. So I wanted to do something creative with the unused fourth CV Pal output.

Max For Live Patch

I came up with a simple Max For Live patch which outputs a MIDI note at regular intervals ranging from half-notes through to 32nd notes. By using this in-line with the Grids emulation and CVPal controller, it acts as a clock source for the Pico Trigger module giving me lots of trigger options for my drum modules.

Goodbye Drum Machine, hello Drum Skiff!

Have decided I needed a few more HP’s for drum synth modules, both to expand my sound palette and add extra modulation sources. So, I purchased a Make Noise 104HP Skiff and have just finished filling it up – isn’t she pretty!

I still want to revisit using Arcade buttons as triggers in the future, but for now this is providing a lot of random percussion fun! This is thanks in large part, to the three Erica Synths Pico modules which give a nice mix of controlled and uncontrolled triggers, lfo’s, sample and hold and noise. And all in bite-sized 3HP chunks!

More tea vicar?

The Bastl Instruments Tea Kick is another of the new modules and it sounds lovely and clear with a real weight behind it, but still very musical too. It’s inspired by the Twin-T Resonant Structure as employed in the Roland TR808 Kick, but capable of a much wider range of sounds. It also has a CV input for tuning along with a separate square wave output, so can even be used as a rudamentary bassline oscillator. This is in the new, aluminium styling, rather than the quirky wooden front panels Bastl normally use but it looks amazing.

Along with the Synthrotek DSM, and a bargain priced Tip Top Audio RS808 rimshot module (Which is more flexible than it sounds), I can now get a much wider range of sounds that really compliment my two Taiko modules.

But, that also means I need a more flexible mixer with extra inputs, so the Tip Top Audio Mix Z fits the bill.

Integration with Ableton Live

As much as I love the self-contained nature of the drum skiff, you can never have enough trigger sources and that’s where the Mutable instruments CV Pal comes in. CV Pal is being used with Max For Live to emulate the Mutable Instruments Grids, meaning I can keep the patterns locked in tempo with my Ableton Live sessions, and a great job it does at that! Dead simple to set up too, so will put together a post on that perhaps. You can get the CV Pal in a kit at Thonk for under £30 (plus VAT) , and it’s well worth looking into.

Eurorack Drum Machine Update

Well, I’m making rapid progress. Have already built the frame for the Eurorack Drum Machine, based around a repurposed Pittsburgh Modular Cell 48 case, and installed three of the modules.

The Akemies Taiko and Pip Slope modules should be arriving early next week.

The Pico Trigger is amazing and really easy to program with the browser based pattern editor which works great from my iPad. 8 patterns can be stored in the module at any one time, even after powering off.

I particularly like the way that each of the 4 tracks has an independent length parameter (1 to 16 steps), great for programming polyrhythmic patterns that change over time.

The arcade buttons aren’t yet functional, but there is a DIY section on the Doepfer website which helpfully explains how to build a manual gate so I’ll start there; just waiting for some veroboard and a 6HP blank panel to be delivered first.

Also contemplating squeezing in a Synthrotek 555 LFO too to add some modulation.

Eurorack Drum Machine

Nearly finished with my rebuild of the modular synth. The Tiptop Mantis Case is full and I’ve also built a second suitcase synth based around modules from Mutable Instruments, Including the ‘Ears’ module which Santa got for me 🙂

So now I’ve turned my attention to building a portable, Eurorack based Drum Machine. Here’s a mock-up of what it could look like…

The core pattern sequencing will be handled through the Erica Synth Pico Trigg module, with the 5 arcade buttons at the bottom allowing me to manually trigger Accent and Choke on the two ALM Taiko modules as well as the Trig input on the ALM Pip Slope.

An ALM PE-1 rounds things off, doubling as a handy 2:1 mixer in addition to EQ duties.