PatchPierre.Net is live

Another small but important step in PatchPierre history;

www.PatchPierre.Net is claimed and live now... easier to remember if you are 'on the go' and want to check out the latest posts.

Service provided by http://www.simpll-solutions.nl/ in Sassenheim / The Netherlands.

SimpLL Solution offers IT-products and -services for businesses

Blind Panels

The regular Doepfer 19-inch Euro-rack system has a usable width of 84 HP. If the modules you install don’t use up the entire 84 HP, you are advised to cover up the empty spaces with blanking panels due to safety and EMC reasons.

As i wrote in an earlier blogpost, the (static) electricity from the system causes the A-100 to be a real dust-magnet.
Blind Panels are available in the following sizes;

A-100B1  : 1   HP
A-100B2  : 2   HP
A-100B4  : 4   HP
A-100B8  : 8   HP
A-100B42: 42 HP
A-100B84: 84 HP

Doepfer also sells the A-100B1.5, a 1.5 HP wide blind panel that for example fits the  Analogue Solutions modules together with eurorack modules of other manufacturers. 

Volts per Octave

The Volts-per-Octave standard luckily turned out to be a quite good one.
A lot of (early) synthesizers manufacturers adapted this standard, 'invented' and popularized by Bob Moog.

Best known manufacturers of early products using the 1V/Oct standard are Roland, Moog, Sequential Circuits, Oberheim and ARP. The big benefit of standards like these is inter-compatibility between products of different manufacturers. It allowes them to communicate better.

The V/Oct standard was wider adapted as other standards, like for example Yamaha and Korg's Hertz-per-Volt standard, that  represented an octave of pitch by doubling the voltage. 
A few synths that use the Hz/V standard are:
Korg: 770, 900-PS Preset, M-500 Micro Preset, M-500SP Micro Preset, Mini Korg, MS-10, MS-20, MS-50, Synthe-Bass, X-911
Yamaha: CS5, CS10, CS15, CS15D, CS20M, CS30
Moog: Taurus I Bass Pedals
Paia: 2720, 4700 Series

The Hz/V standard was used before the log converter was used in VCO's and is essentially linear control as can be found on various signal generators and function generators like those used by the BBC Radiophonic Workshop before they got a VCS3*. There are/were solutions available that convert from  Hz/Volt to V/Oct and vice-versa.  ( like the Korg MS-02 ).

No wonder that the A-100 system uses the V/Oct. standard. You can easily synchronize your system with almost any (old) machine that you have lying around, and most MIDI-to-CV converters use the same standard too.

For example i love using the CV (and Gate) output of my Roland TB-303 to control my A-100 system. The signal arrives at my system via a  A-180 2x4 multiple, so i have 3 copies of both signals available at any time.
Sometimes i use the CV slightly detuned for an interesting effect, sometimes i put it through a voltage inverter first, something that doesn't work out with all your 303-lines because of tuning.

The Gate output (trigger) of the TB-303 can be sent through a delay for some more interesting echo-like effects.
There are so many possibilities for your other gear to communicate with your A-100 with the 1 V/Oct standard... just go ahead and try... and amaze yourself.

*thanks to Tony Steventon for additional info

SiteTip I : Tone's Analog Synthesizer Projects and Products

I stumbled upon this interesting site last week; Tone's Analog Synthesizer Projects and Products. You can find it at http://synovatron.blogspot.com/
The overall site looks like a good start for everyone who is busy with, or starting on eurorack synthesizer DIY-ing and is operated by Tony Steventon, a UK electronics design engineer with a long interest in synths.
"Like most ideas it came out of trying to solve problems..." he wrote to me "... I could not fit either the jack sockets or bracketed pots on to standard 0.1" perfboard and came up with this idea over a year ago".

He continues "...several people have expressed an interest in learning how to take an idea through to a design and onto a prototyped module which I am quite tempted to do as a future 'learning' page on my blog..." "...I am working on my CV Tools module at the moment, which I have prototyped using my kits, but when that is ready for manufacture I am happy to consider some more ideas, I already have four promising ideas which may get developed either on my own or in collaboration with the idea originators."

Along with selling different DIY sets and prototyping kits, you can also order additional components for reasonable prices here. Listed are various Control pots (50k linear supplied as standard but 10k linear, 100k linear, 1M logarithmic or a mixture are available upon request), Pot mounting brackets, Decoupling capacitors, 16-pin headers, 3.5mm jack sockets, Red/green 3mm 2mA LEDs, TL084 quad op-amps (DIL), 14-pin IC sockets, 16mm soft-touch knobs (red, grey, orange, green, white, blue, yellow pointers), 10uF 16V electrolytic capacitors, 100nF ceramic capacitors, Headers - single, double, straight, right-angle, DPDT toggle switches to fit DIY2,  ...and more on request.

The site has an interesting (and growing) support page with all the datasheets and other practical tips on synovatron products. More info and discussion is possible at his dedicated Forum.


For sales, support and combined shipping enquiries you can contact synovatron@btinternet.com
CAUTION: These kits are intended only for experienced experimenters and constructors to prototype their designs. It is possible for you to destroy components or damage your synth if you are not careful. It is recommended that you use a separate regulated ±12V power supply for experimentation.

Filters I : A-127 Triple Voltage Controlled Resonance Filter

It is hard to say what my favorite A-100 filter is. Every filter has its own distinctive sound, and they all have a lot of Control Voltage input possibilities. I must admit i prefer low-pass filters... and filters with many outputs.

The A-127 VC Triple Resonance Filter is 3 bandpass-filters in one, each with its own LFO (sine) with adjustable frequency. The module has 3 individually adjustable outputs plus a mix output, and with all the controls for filter frequency and resonance it is a very flexible module.
\All 3 filters have an external CV input too, that by-passes the LFO when a plug is inserted in the socket. The amount of incoming CV's can be attenuated with a knob.

I love the sound of it, one of the characteristics of the 12 dB/Octave filters is that it can produce almost vowel-like sounds.
The LFO's can create amazing filter-sweeps as well with the frequency-rate adjuster.
As modulation inputs various CV's can be used like ADSR's and other LFO's (triangle/saw/rev saw).
Inputting voltages from any Wheel, Joystick or Theremin modules are also awesome ways to control this massive module.

You can even turn this module into a Triple Low-Pass Filter by changing internal jumpers, another nice feature. It might not be my most favorite filter of all, but this one is still the most-used filter that i own at the moment...

Busboard Access

Updated August 25th 2011

A good patch can sometimes turn out to a whole spaghetti of patchcables.
Luckily Doepfer provided the A-100 system with a subsystem that makes the routing of some Gate and CV signals through the internal busboard-system possible.

It's too bad that not all modules have this ability, but for some modules this is a good way to avoid "over-wiring" your system with patch-cables.

Only modules A-110 (Standard VCO), A-111 (High end VCO), A-111-5 (Mini Synth. Voice), A-140 (ADSR), A-164-1 (Manual Gate), A-185-1 (Bus Access), A-185-2 (Precision Adder) and A-190-1,2,3 and 4 (Midi Interfaces) have access to the CV or Gate signal of the A-100 busboard.

The A-164-1, A-185 (-1 and 2) and A-190 (-1,2 and 3) can be used to "write" the busboard, i.e. they can output the signals to the bus.

The others are able to "read" the busboard, i.e. they pick up the signals CV (A-110, A-111, A111-5) resp. Gate (A-140, A-164-1) from the bus.
The A-111-5 can pick up CV and Gate from the bus. Also the planned A-143-4 Quad VCLFO/VCO will be able to read the A-100's busboard.
For details please refer to the user manuals of these Doepfer modules.

Most of the modules come with jumpers inside that can connect or disconnect the signal from and to the busboard. If other modules should be able to "write" or "read" the bus some of them can be modified. More on this in a future modding blogpost.

Doepfer warns on their DIY-site for shortcircuiting modules and/or busboard, so please take note:
Pay attention that only one module is allowed to "write" to the same bus signal.  If two or more modules write to the bus this leads to a short circuit of the corresponding outputs.
Please let me know if i forgot some modules in the Feedback section of this post, thank you!

Quotes II : Tom Rhea

" Sound is sound. There is no such thing as an 'artificial' sound - only sound or silence.
A synthesized sound is not a replacement for a 'real' sound; all sounds are real "

Dr. Tom Rhea - Electronic music historian

Happy Knobbing III - New Joystick-Lever

The latest minor modification to my A-100 system  is the replacement of the A-174 Module's joystick.

I finally changed my black plastic lever with a newer aluminium one that i ordered at Doepfer last week.

Modules before 2007 had the black plastic lever as standard, all modules delivered after 2007 already have this aluminium lever.

It's just a small optical change, nothing more. The new lever is a bit shorter, but does have a nice/better grip though. And that for only 10 Euro's...

<  Old vs. new lever

A-134-2 Dual Voltage Controlled Crossfader

 My latest ( my 60th! ) Module is the A-134-2 Dual Voltage Controlled Crossfader.

This module, that contains two identical voltage controlled crossfader units can be used in combination with controller modules like the Wheels or the Joystick controller to make fades between different sounds  ( or even control signals like LFO's ) 

Each unit has two voltage controlled amplifiers (VCAs) with opposite control behaviour.

In standard (assymetrical) mode, with 0 volts CV added to CV1, input A is fully closed and input B fully opened.

Adding more control voltage to the CV1 input will result a volume increase at input A and a decrease of the volume at input B. In the middle position you will hear a nice mix of the two inputs.

Different settings for the module are available, by switching the internal jumpers you can make the CV inputs ready for bi-directional voltages ( positive and negative ).

By coupling both units you can even control 4 inputs with, for example the A-174 Joystick Module's control voltage, where the centre is the 50% mix and each 'corner' of the joystick is an individual input. A truly amazing and very versatile little module...

Booktip III - Synthesizers by Hans de Vries ( in Dutch Language )

This little Dutch book, written in 1983 (!) is probably one of the best synthesizer-technology-books that I own. The fact that it is written in Dutch wasn’t enough reason to keep this book out of this blog.

In 144 pages, Hans de Vries explores the basics of sound creation.
The first half clearly explains the basic building blocks of synthesized sound, very clearly written (... but in Dutch, remember...) and with lots of graphs and explanatory pictures ( b/w )

The second half of the book delves more into the use of synthesizers in practical situations like (home-) studio’s etc.. The book ends with an overview the most popular or groundbreaking (analog) instuments of that time, like the Korg MS20, various Moogs, Oberheims and Rolands, up to the fisrt digital synthesizer; the Yamaha DX-7

Funny detail in this book is the writer’s skepticism towards MIDI and Computerized sequencing. Remember... around 1983 there were only a few instruments equipped with MIDI, and computers weren’t cheap. Above that, computer-sequencing-programs were not widely available back then.

ISBN: 90-201-1642-8

Oscillator Synchronizing

Interesting sound-effects can be obtained by the synchronising of (multiple) oscillators.
In a typical setup, one oscillator (master) restarts the cycle-period of the other one (slave) , what results in equal base frequencies on both oscillators. This is called Hard Sync.

The result is an irregular waveform with it's own harmonic spectrum, completely different from 'standard' waveforms

Soft Sync is a more general name for all kinds of oscillator synchronisation.
This form is very similar to Hard Sync, but here the slave oscillator is forced to reset to zero with every cycle of the master regardless of position or direction of the slave waveform, which often generates asymmetrical shapes.

In Soft Sync, rather than resetting to zero, the wave is inverted;  its direction is reversed.
Further variations to the sound can be made by comparing the sounds with different comparison tresholds. For more info see the Wikipedia page on Oscillator Synchronisation
Soft Sync sounds smoother  and distinctly different from hard-sync.
It is difficult to replicate this effect on digital synths, due to aliasing problems.

Soft Sync-like effects can also be created with other modules, for example a phaser or a Phase Locked Loop (PLL) Module.