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!
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.
Today was day one of Ableton‘s #LoopAtHome and they set a challenge to build and record your own ‘Gizmophone’ instrument. Unfortunately, I had urgent gardening to attend to (?) so only managed to hack something together at the last minute, using whatever scrap items I could find. This included an offcut of windowsill, a metal Ikea leg and some old wire I found at the end of the garden. And this is the result…
I did manage to include a Piezo condenser mic too, but it had terrible background hum, so only really worked for short percussive noises which I combined into an Ableton drum kit. I also dialled in a smattering of the Corpus effect to make the sounds ring a little more, but only at 5.5% wet.
Some sounds were actually Ok!
The revelation though was the metal Ikea leg. When tapped with a spanner, it made a high pitched bell tone that was (almost) in tune. I created a patch using Ableton’s sampler instrument, sorted out the tuning then duplicated it with slightly different filter settings before panning each version slightly left and right.
Another technique that worked really well was swirling and scraping the spanner inside the wire springs, which created a lovely rhythmic texture which I layered behind the main percussion sounds. Lots of editing of warp markers in that one, as well as some Beat Repeat to add variation, but really pleased with the end result.
I created a quick demo of my ‘instrument’ so you can hear what it sounds like. Some additional kick, snare and synth bass was added to fill the sound out.
And if you fancy having a look ‘under the bonnet’, I’ve even zipped up the Ableton project folder too!
It only uses stock Ableton plugins, so should work fine (have tested on my Microsoft surface and iMac) – Ozone Elements is on the master channel, but you can just ignore that if you don’t have it installed yourself.
Not sure what the plural of Mantis is, but I now have three of the Tip Top Audio cases of the same name, laid out end-to-end on my desk like a mini mission control.
Analog Synth Mantis
To the left is the Analog Synth Mantis which is probably the more ‘vanilla’ of the three cases. Built around three different oscillators (OSC303, Tip Top Z3000 and the Doepfer A-110), each with a separate, dedicated filter (VCF303, Intellijel uVCF and Doepfer A-105 respectively), as well as the usual array of VCA’s, ADSR’s and LFO’s (Mainly Doepfer or Erica synths modules).
Dinsync’s excellent Modseq module allows me to do some repeatable Sample and Hold style manipulation of the filter cut-offs, or paired with the Ladik Easy Quantizer module, makes a mean bassline sequencer for the OSC303.
Other modules of note include the FoH Choices joystick, which is paired with the clever little Ladik Joystick Math module which makes it a lot more flexible, and a small selection of Make Noise modules including the Moddemix and LXD which are both great for teasing out plucky, percussive sounds.
Digital & Sequencing Mantis
The middle, Digital & Sequencing Mantis has something of a split personality. The top row provides the master clock for the whole system, which I have distributed between the three cases using a combination of different powered multiples to create a semi-permanent clock backbone.
It also provides additional sequencing and quantizing capabilities, courtesy of a Turing Machine with the Pulses and Voltages expanders and the GMSN Pure Sequencer, both paired with Doepfer A156 Dual Quantizer. These are great when I want something a little more unpredictable than the ES-40 / Ableton Live combination or my Beatstep Pro. Alternatively, the sequencers work great as modulation sources for my percussion modules.
The lower row houses my ‘Digital’ modules, including the obligatory Mutable Instruments trilogy of Braids, Rings and Clouds, as well as Erica synths Black Hole DSP which has some lovely Shimmer effects. A Mutable Music Things ‘Ears’ module rounds things off, used primarily to trigger the strum input of Rings.
Gates & Percussion Mantis
Moving to the right we have the Gates & Percussion Mantis which has a wide variety of drum and percussion modules as well as gate triggers, clock dividers and logic modules which are great for coming up with abstract drum patterns.
The sound sources themselves include the ALM Taiko modules (Still on the lookout for the limited Haswell’s Taiko if one ever comes up on eBay or Muffwiggler), multiple kick drum synths (With the Hexinverter Mutant Bassdrum being a current favourite) and a selection of Tip Top Audio 808 modules.
It’s worth remembering that percussion modules don’t have to be limited to providing drum sounds though, as many have pitch CV inputs which allow you to use them for basslines and tuned percussion alike. They also often have built in VCA’s and envelopes, further increasing their effectiveness for a relatively low cost.
Also in this case are some additional effects courtesy of the Sara VCF filter from DinSync, ALM’s EQ and Music Thing’s Spring reverb module. There’s also a passive ring modulator I made with some germanium diodes which is pretty unique sounding.
And last but not least, we have the Audiodamage ADM09 USB audio interface which is normally linked to an iPad 3 running the stunning Borderlands 2, granular synthesis app. You can coax some amazing sounds out of Borderlands, particularly when feeding it a diet of modular synth noises from the ADM09.
One day, I might even learn what it all does 🙂 Seriously though, I’ve just signed up to the Learning Modular Patreon page which gives regular hints and tips on how to get the most out of your modular synth, as well as free access to a course of your choice on the main Learning Modular site. Can’t be bad!
I’d hope I’m comfortable with the basics, so went with the ‘Level 2 Eurorack expansion’ which is very comprehensive and appears to be regularly updated to keep it current. Chris Meyer who created and presents the course has a great knack of making complex concepts sound easy and I’m learning so much already. Here’s an excerpt from the course…
The only danger is that I’m now lusting after a Mordax Data module, having seen Chris demonstrate his one. I’m sure I can make it fit somewhere 🙂
Well, this house building business takes a lot more time than I had expected, and whilst I’ve become something of a dab hand at building airing cupboards and fitting out utility rooms, I’m finally coming out of the other side and getting a bit of time to work on my music.
I’ve recently taken delivery of a third Mantis case (someone should have told me this Eurorack hobby would turn into an obsession!) and am working out what modules to put into the gaps.
As you can never have enough filters, I decided to go DIY and search for something interesting for the last 8HP of the ‘Analogue Synth’ Mantis case.
This led me to a PCB and Panel kit by Guru Gara Synth, based around the 4-pole 24dB CEM 3320 filter. The filter was used in lots of classic 80’s music technology including most notably the Prophet 5 synth (Rev. 3), the Fairlight II, PPG Wave 2 and the Oberheim OB-SX – none of which I would ever expect to be able to own! (Unless Behringer feels like cloning them of course).
The kit doesn’t come with any build instructions, but the PCB is very clearly laid out, so that’s no biggie. As the CEM3320 has been out of production for some time now, I went for the AS3320 from soundtronics.co.uk which is a modern equivalent and very reasonably priced. From the YouTube videos, it does sound rather nice!
More info on the 3 Mantis cases themselves and how I’ve configured them in a future post.
I don’t often use guitar pedals, but they are good for creatively messing up the ‘clean’ sounds from my synths. It was always a bit of a hassle setting them up though, and as you know I like a project, so I put together a basic pedal board. All fairly standard stuff, but I introduced a mini mixer in the chain so that I can mix the wet and dry signals from the delay. It also allows me to create some feedback loops by using output B from the reverb and putting it into Input 3 on the mixer.
My requirements were also that they should be powered off of a single plug. The pedals were straightforward in that regard, but the mixer used 12v rather than the 9v pedal’s typical need.
The solution came in the form of the Donner DP-2 Guitar Pedal Power Supply, which has 10 outputs including one at 12v. The included power lead didn’t fit the socket of the mixer though, and I also needed to invert the polarity too, so had to invest in a couple of adapters which did the trick!
Some cable ties helped to control the rat’s nest of wires underneath and I added some castors too. Originally, there were 4 castors, but I decided to remove 2 of them so the board tilts at a nice angle.
The photos look a little wonky, but that’s just the angle of the photo – they are square, honest!
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, 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.
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.