A-130 + A-131 Voltage Controlled Amplifiers

A Voltage Controlled Amplifier ( VCA or variable-gain amplifier) is an electronic amplifier that varies its gain depending on an incoming control voltage (or CV).
It is one of the most basic building blocks for a modular synthesizer.
Find more on this on Wikipedia.
Modules A-130 and A-131 are very simple VCA's that can be found in most basic Doepfer systems.

For audio signals, you would normally use the exponential VCA (A-131), and for control voltages the linear VCA (A-130), but it doesn't always have to be that way, though.

The amount of amplification of the VCAs is determined by the voltage at the CV input and the position of the gain control, which sets the overall gain in the system.
The VCA has two audio inputs, each with an attenuator.
They are amplified by the combination of the gain and the two CV controls.

Remark:
The old versions of A-130/131 (those with CEM3381/CEM3382, which are actually 2 VCA's on one chip*) are not able to process slowly varying control voltages (AC coupled in/output).
The newer versions of A-130/131 (those with CA3080) are able to process even slowly varying control voltages (DC coupled in/outputs).

*it might be worth investigating these a bit more for a future DIY treatment

Most Wanted Update - MSY2 Module for A-100 System

Old Version of the MSY2,
the newer ones are in black

Great news...

It looks like the idea that i posted in December 2010 for some kind of extended version of an MSY2 module for the A-100 wasn't that bad.

In the Yahoo Doepfer A-100 Usergroup Dieter Doepfer recently announced that they "...are working on a modular version of the MSY2 with some additional features ( USB interface, several outputs with different clock dividing factors and polarity and some more )."

The MSY2 MIDI-to-SYNC/Clock Interface can be used to convert Midi clock into analog clock signals.

There is no release date or price available so far.

A-138 Linear/Exponential Mixer

Module A-138 is a simple four channel mixer that can be used for either control voltages or audio signals. (although i hardly ever use one for CV)
Each of the four inputs has an attenuator, and a master attenuator, so that the mixer can be used to interface directly with an external mixer, amplifier, etc.

There are two versions of this module:
A-138 a: potentiometers with linear response, especially suitable for control voltage mixing.
A-138 b: potentiometers with logarithmic/exponential response, especially suitable for audio signal mixing.

The latest version from April 2004 is an improved version of the module A-138b.
For the revised versions control In1 works as a DC offset generator (about 0...+5V) provided that no patch cord is plugged into socket In1.
If this feature is not required it can be deactivated by removing a jumper on the pc board.
In the summer 2004 the A-138a was introduced with this improvement.

In the summer of 2007 Doepfer also released a mix expander module A-138x, that increased the number of inputs of the A-138 by five.
That module was discontinued last year...

Sample and Hold with Doepfer A148 by Raul Pena

Raul Pena from http://raulsworldofsynths.com/ just posted a few new video tutorials.
Here are the first six (of seven!) in a series dedicated to Sample and Hold,Track and Hold, and comparisons with the two.

Video 1 : Track and Hold Vs. Sample and Hold with Doepfer A148 S/H
http://www.youtube.com/watch?v=KvjiKzBaTAs

" Demonstration comparing Track and Hold with Sample and Hold using the Doepfer A148.Sound and Video by Raul Pena."

All other A-148 video's after the break

Most Wanted VI - Special Vocoder MIDI-interface

I read the following text on one of Doepfer's A-129 vocoder system pages a long time ago, but it is still on Doepfer's website;

" A special MIDI-interface for the vocoder system is planned.

The basic functions are a 16-way CV-to-MIDI interface and a 16-way MIDI-to-CV interface (way 16 will be used for other functions like controlling slew-rate or voiced/unvoiced).

The CV-to-MIDI section converts the CV outputs of vocoder analysis into MIDI controllers which may be recorded by a computer sequencer. 

The MIDI-to-CV section converts incoming MIDI controller information into CV's for the vocoder synthesis section. 

Additionally we plan to store some factory and user definable 'vocals' in the MIDI interface so that you may call up complete vocals (like 'a', 'e', 'o', 's', 'sh' and so on) by MIDI program change events (may be we use another MIDI event type for this purpose). 

Thus the vocoder system will become a universal MIDI controlled filter system not limited to the standard vocoder features. "

Okay, i must say that it all sounds impressive and also very useful.
I do hope this module will be taken into production, but i believe this has been
on Doepfer's webpage for a while now, which makes me think that this module will probably never be made.
It might be in the Universal 12 bit AD-processor-DA module plans, because these things do need some processing power but i'm not so sure about that...
With all the announced features you could imagine this would not be a cheap module to make, but we'll see though...

Find more of my 'Most Wanted' posts HERE

Wooden Ribbon Controller Project Part 2

My project is going great so far.
Most of the woodwork seems to be finished.
I carved out the whole  59.7 x  2.4 cm. strip where the fingerboard should come, about 3 mm deep across the whole surface.
I carved a bit too deep at places, but i will fill that up a bit with filler, so that should turn out fine.
The pressure sensor needs a flat surface, so that needs a little bit of extra attention.

I painted the wood 4 times now, with a glossy mahogany varnish, and it looks quite amazing IMHO...
It will get one last layer of varnish after the final assembly of the whole project
I screwed an iron ring at the top (but that might become an brassy one), and i am planning to screw one at the bottom for  attaching a shoulderband.

I changed my mind a bit about the old fingerboard that i wanted to use, but i will order a new pressure-board from Doepfer next week.
I also need to find a smaller piece of wood that can cover up the USB-connector or find another good way to hide the connections.

That does mean i have to wait a few weeks before i can take the last steps and finish the whole project.
I will keep you updated...

A-146 LFO2

Module A-146 (LFO 2) is a Low Frequency Oscillator, which produces periodic control voltages over a wide range of frequencies.
The LFO can be used as a modulation source for a series of modules (for example pulse width and/or frequency modulation of a VCO, modulation of a VCF cut-off frequency or amplitude modulation with a VCA).

It is quite different from the A-145 and A-147, that i discussed earlier HERE

Three outputs are available, with different waveforms: sawtooth / triangle; square wave, and positive-voltage square wave.
The waveforms are continuously adjustable from rising sawtooth, through triangle to falling sawtooth.
The same control affects the pulse width of the square wave.
A three-way switch can select one of three frequency ranges, spanning from one cycle every few minutes, at the lowest, up to audio frequency at the highest.

A nice LFO, but i don't own one myself... yet.
Too bad it has no CV input  and that it doesn't have a reset input...

More on waveforms: http://en.wikipedia.org/wiki/Waveform
also see Wikipedia for more indepth info on the different wave-forms:
Pulse wave             Sawtooth wave
Sine wave               Square wave
Triangle wave

Wooden Ribbon Controller Project Part 1

Today I decided to pick up an old idea that i had for a long time.
Whenever i play the Ribbon Controller, i tend to hold it like a guitar, not like most do on a tabletop surface.

I have always loved the combination of wooden elements and synthesizers.
This combination was/is still very popular since the early 1970's.
Look at all those (Mini)Moogs and many other synths with wooden side-panels for example...
That is why i also decided to make my Ribbon Controller out of wood.
It looks like a found a nice solution to an earlier project too.

So today i bought myself a nice piece of wood in the local woodshop.
On forehand i had the idea that the handle of an axe might be the kind of thing that i needed.
They had a few different sizes, but i found a hardwood unpainted axe hande that was 90 centimeters (3ft.) long and perfectly shaped and curved.
I might make it a bit shorter later, but for now this will do just fine.

I dismantled my old Ribbon Controler (i do own another one, the newer version) and drawn out the shape of it on the axe handle. I used 3 screws to fixate the fingerboard while doing that.
Next up is the carving... i want to sink the fingerboard into the handle, but that means i need to carve at least half a centimeter deep.

I already carved the first bit like the last picture shows, but i still have a long way to carve.
But i need to get myself a new chisel now so you will have to wait how this project will continue.
I will keep you updated... but don't expect this to be finished before 2012.

Ribbon Controller versions

Ribbon controllers, old model on top

One of the most used parts of my modular setup is without doubt my A-198 Ribbon controller.
You can read all i ever wrote about it so far HERE.
I love improvising with the manual controller and the sensitivity of the manual makes it fun to play with.

In combination with the A-156 Dual Quantizer and a A-170 Dual Slew Limiter it is quite easy to play, even for beginners.*
Together with and the different scales that are available on the A-156 you can make your ribbon-sliding-skills sound very impressive.
* I should note that is also easier to play the Theremin modules using these two modules.

From 2005 the A-198 (and R2M) manuals are equipped with an even more sensible pressure sensor.
The improved sensor now works along the entire manual.
So how can we distinguish these two models?
The newer version is white on top, instead of the greenish grey color of the old model's touch-surface.
The new version also does not have the text 'A-198' printed on it.

Ribbon controllers, new version at the bottom. Note; the orange stickers are not standard

The Doepfer R2M (Ribbon-to-Midi) is the stand-alone version of the A-198 with MIDI and CV/Gate outputs. R2M offers a lot more features than the A-198 (e.g. quantizing, gate function even in the hold mode, inverse scaling and many more)

Currently from June 2011 the cases have changed from silvergrey with black printing to black with white printing... also very slick...

Doepfer A118 Filtering with A120 VCF Low Pass Filter

More Video from Raul Pena (of http://raulsworldofsynths.com/)
This time almost 45 minutes long tutorials on using the A-118 Noise/ Random Voltage Generator in combination with the A-120 Moog Style Low Pass Filter... creating some interesting wind-effects...

Video 1 : Doepfer A118 Filtering with A120 VCF Low Pass Filter
http://www.youtube.com/watch?v=vin9o4GpJs8

" Part One Discussing the features of the Doepfer A188 Noise and Random Voltage Source module. Followed by a Demonstration of Filtering white and Colored Noise with the Doepfer A120 VCF Low Pass Filter. Sound and Video by Raul Pena. "

Video 2 : Doepfer A118 Filtering with A120 VCF Low Pass Filter Part Two
http://www.youtube.com/watch?v=9ZxRsxPLuI4

"Part Two Ongoing Demonstration of Filtering white and Colored Noise from the A118 Noise module with the Doepfer A120 VCF Low Pass Filter. Modulation Capabilities also explored with A147 VC LFO and A145 LFO. Sound and Video by Raul Pena."

Read more on the A-118 HERE
Read more on the A-120 HERE