For a long time I have been toying with the idea of creating a Control Voltage tuned Radio that I can DIY and add to my Eurorack Modular Synth setup.

There are a ton of uses I can see in having easy access to the radio waves: random noise, strange sounds, fuzz and white noise.

But being able to control the tuning with CV so I can jump around the dial, or slew my way from one spot to another I think would be really awesome.  If for no other reason than I like the idea of programming up a sequence and then every time it runs it will be different since the sound source is constantly evolving and changing.

So research began by looking at how radios work, and things didn’t look good to start off.  It seems that radio tuning is all about capacitance, not voltage.

The simplest tuner consists of an inductor and capacitor connected in parallel. The capacitor is usually made to be variable (although the inductor can made variable it requires a more complex mechanism and is rarely used). This creates a resonant circuit which responds to an alternating current of one frequency

http://en.wikipedia.org/wiki/Tuner_(radio)

This means “most” of the time the tuning pot is not a pot but a variable capacitor type thing, which means you can’t just swap out the pot with a CV source (which was my initial hope, ignorance is bliss).

All seemed at a lose until I found out that some radios use what is called “varactor diode tuning” this is a diode that in essence replaces the capacitor bit, but the neat bit about the diode is that it’s voltage controlled.  This means that the tuning pot will be handling voltage and suddenly we have somewhere we can bolt our CV into.

The next snippet of info, was that Ramsey (the makers of great electronics DIY kits) make a series of kits that all use Varactor Diode Tuning, include a $40 FM receiver kit.

So later part of 2010 I ordered one up, and it sat on a shelf for a few months whilst I tried to finish off other “higher priority” projects.

Then NAMM 2011 came around, and I was intrigued to see that Buchla, the makers of VERY high end modular synths was showcasing a new module the 272e which had 4 FM receivers that could all be referenced via CV.  Now their concept is very different to mine, they have digital tuners that you tune and they then allow you to control the outage from each using complex envelopes, there is no CV control of the tuning – that said they do look really very nice indeed.

Buchla patch Model 272e through the 296e Spectral Processor. from Richard Devine on Vimeo.

But if nothing else it spurred me back into life.  So earlier this week I soldered up the Ramsey kit.

With some awesome help over on the muffwiggler forums (MANY THANKS DAVERJ!)

I tapped into a couple of places on the PCB and hooked it up to a very low frequency Oscillator I had running a sine wave, and low and behold I had CV controlled tuning.

Now the tricky bit.  I doesn’t work great. It doesn’t work with CV only with the Oscillator, so it needs a stack load more tweaking and testing.  But my hope is in the next week to get it hooked up to Silent Way and have a fulling CV tunable radio incorporated into my modular synth.

Quick test patch, to see how we can control the ES-1 module from Expert Sleepers using Max/MSP.

Usually the ES-1 is controlled by Silent Way (which has a ton of awesome functionality; calibration, quantizations, LFO’s etc. But i really wanted a way that I could quickly get up to my neck in craziness using max/msp to control the ES1, so this is my first quick test.

Is it just me or does it seem exponential the sound (and Hz increase on the toptop z3000) as you slide the amplitude slider to the right?

More coming soon…

Patch Attached Below:

----------begin_max5_patcher----------
657.3oc0W0ziaBCD8L4WgkOVklZa9HPus8P+CziUqpHfSVWA1Tvnlrq17auF
CjjskDbBDz1KfX.m48dya737xLK3JwVZAD7Yv2AVVuLyxRGpJfUyyVvzvsQI
gE5OCReNNLZObd8q3koLdBUpeG4XPQorMJpIZVnL5IFeyOxoQx5LZ6u.MGPr
WVcyws8J3wlkvh0oTr5meD6Aqh85rYUWlaHXiDooTtrEsR5VclgeSTxiAB9m
DqW2IUvMAWK3xB1yTcLxBzUyPMoHXb0MrKR+D5LTzEdRV4go5rBeHmElLlj+
gzrDlrLldWYNwknIqmALe4zP7ulS+UIkGs69VxqM0tFva6wk2JHthlObxQNO
4bH0DxKn5VGrq9mQtKiVu.HqpP.fqB4afc55cFWQnHRjQuk8mVUttUY7sOuB
fQZpais0bO3Xmcmry9l3PBKtmB4a4.9B1QcCnSPckRCZa6KUv5tJQNTkRDgR
0hxJkml4CRGBojhaw7R+sJQ+SOaNnpq8KcpEnqwTeAIB6oG.Enu5h62S2sDg
+uqaF6p2qBW6QFktYzHKBc6JJXa1ObkA2ux3421vzmxnfDWwwtDkfwUSTcfJ
dbWMFj.2S5HLvWn2U3hNC+IwX7g8.7E26enFCR63cGswfrvc.FCuQdzW+iMR
KSzDQg3qdRRyI5F5nDWCmjfG2AIQ6hRn6UlYzc0efcVVehes7Tu8wM6OHl4O
zKElv3+8+jSiup3uUtJDk4Qsou8LXfiPLlVHY7PISvO8iTmVEfO7QOwhio7S
GCmxhyDpADMf.7XmEOSwjmoPBMYPp5PP8iIzjho.CfDYZUIjAPJXZgD98Wgy
2.H4MocbtFfH+IUiHFpQn2W6JMDHod30Y+waXj2r
-----------end_max5_patcher-----------

Ever since buying a couple of modules, I’ve fallen in love with analogue modular synths, they are addictive beyond belief and I’ve yet to find anything as engrossing as standing in front of it twiddling knobs for no apparent reason generating all sorts of swirling modulating filtering noise. I can loose hours very easily. As always though I’m never satisfied and I want to tinker. One of my projects I’m most actively researching is the idea of an arduino based Step Sequencer.

There are a million threads online with people desperately trying to get their trusty arduino’s to generate control voltage. The problem you have is that the arduino doesn’t live in a real analog world, it’s all about the digital. The only smooth it can do is PWM, and even then it’s really not go lovely to listen to. There are huge threads about people applying filtering, or faking analog with complex software, or powering 8bit, 12bit 16bit DAC and the huge amount of arduino sketches needs to handle them, and to be honest it’s totally terrifying for something that is as easy as turning a pot. So I decided to take a different approach. (if you really want to make music with an arduino, go see midivox, I just got a couple and they kick ass)

I want to keep the analog signal pure, and only handle the step side of the equation using the arduino. So the initial idea would be 8 pots, 1 thru 8. a single CV in, a single CV out. The arduino would be hooked up, so that when messages are sent down the USB connection, current passes thru 1 specific pot and comes out the other side.

So I can set up my “notes” with the analog pots, and then just trigger which one, when, how long and what order they get “played”.

After this initial prototype, I’d shoot higher and aim for 3 or 4 rows of 8 each with their own dedicated CV in and out, and gate outs, and tempo outs, and LED’s flashing, and a front accessible USB port, and way to store sequences on a memory chip that is slotted into the front and sequences chosen using nothing but the power of the mind, etc etc etc.

It seemed like a no brainer DIY project, that maybe one day would lead to PCB’s and kits and open source and all that stuff I aspire to do.

Due to my limited real knowledge thought I’m already overflowing with questions. First of which is how I do this, and what’s the best “switching” mechanism should I use. Should I use relays, optoisolators, Voltage controlled resistors, transistors or just good old plain Jane relays. I have some open question on the arduino forums so hopefully I’ll get some validation for my madness. Any suggestions feel free to jump in.