Filters III : A-124 Wasp Filter

The A-124 is a special 12dB multimode filter using the filter circuit of the EDP Wasp, a monophonic black and yellow analog synthesizer, that was built around the end of the seventies and manufactured by the UK company Electronic Dream Plant.

I totally love the sound of the A-124 Wasp Filter module. It does have it's own special sound due to the special circuits in it which makes the module sound a little dirty and distorted. This can sound very nice with extreme filtersweeps, i often control the cut-off frequency with the pressure CV from the A-198 Ribbon Controller.

The module has 2 audio outputs; a band-pass and a combined low/notch/high pass output that can be controlled with the 'mix' knob that defines the relative amounts of low and high pass signals.
( middle position is notch )

One downside of the module is the lack of a QCV input like most A-100 filters have, so sadly the Resonance cannot be controlled via an external voltage. You can only adjust this manually.
It would have been nice if the Mix could also be controlled by CV...   IMHO

Out of the box this filter can't go into self oscillation, in contrast to most of the other filters in the A-100 system, but modifying  for self-oscillation is quite easy;

Soldering a 10k resistor in parallel to R13 (27k) leads to self-oscillation of the filter at the max. resonance setting of the resonance control.*

 More info on this modification can be found HERE

100th PatchPierre Post

Woooooot! ...again. :-)

My 100th post already (the 50th was on December 7, 2010), and the blog is still going strong.
With fewer posts though, but the viewing rates are still slightly growing every month.
Thank you all again for regularly visiting this site and for your valuable feedback.
I hope my blog can still please the people who just got into analog (modular) synthesizers, and also provide the more advanced users with interesting links and different insights.

In this post i would like to take a quick look into the most popular of my first hundred posts.
Although i cannot exactly tell how many people read each post (many of the visitors land on the main page, where they might read multiple posts at once), i can tell by the individual clicks what the most popular posts were and tell a bit about their traffic sources.

By far the most popular post was my Busboard Access post from November 17, 2010.
I guess struggling for hours through the manuals for a complete overview of all modules that are capable to read or write to the A-100's busboard was worth it.

Also still very popular is my PatchPierre Mobile App for Symbian post from December 8, 2010.
I am still very proud with the almost 5000 installs of the application on Nokia Symbian and selected S40 devices. I do hope Nokia will find a way to port these kind of self-made apps to the Windows Mobile platform and Market too. The more installs, the better... :-)
I did get an email from OVI that my App will soon be updated with some new extra features and an 'enhanced user experience'. A blogpost about that will follow...  (meanwhile the app is still available HERE)

The A-101-2 Vactrol Low Pass Gate and  A-156 Quantizer Follow Modification posts were also quite popular, together with the various other DIY and Modifications posts that i did.
The Book-tips and the CD-tips also seem to be of your interest. I still have a few book-tips on the shelve, and i will try to post some interesting (synthesizer-related) CD-reviews in the near future too.

And... where did all this traffic come from?
Well, Google's search in all its varieties ( .com /.co.uk /.fr / .de / .nl ) was by far the #1 top referring site, but that is hardly a surprise.
Social Media-sites like Twitter (#2) and Facebook (#4) also proved to be very useful to attract readers to the site, and  a lot of viewers came from the Nokia/Symbian mobile application referrals ( #5, but not as much visits as i expected, a lot of people still seem to only read my blog in-app, thus still missing out on a lot of the links ).
More surprisingly was the #3 spot, because Tony Steventon's Synovatron.blogspot.com seems to have been a true link-farm for links to my blog. Thanks for that Tony ;-) Keep up the good work with your interesting projects!
The link to my site on the Doepfer A-127 webpage has also attracted quite a few (new) readers, i'm pretty proud with that one and it looks like the MuffWigglers have (re-)discovered/ finally found this blog too. ( thanks to THIS post ) I have seen a lot of traffic coming from there in the last month... Welcome!

I hope i can serve all of you with at least 100 more posts in the future, but it might take bit longer than the first 100...

Saving Patches

One of the downsides of a modular synthesizer is the lack of memory banks.
There are times when you have finally found that perfect sound, but need some modules for other patches...
A good (photographic) memory will often do the job in the more simple cases for anyone, but for bigger patches you might need a little reminder sometimes.

To 'store' patches you have a few options;
First, always try to sample the sound you made with a (hard- or software) sampler. Although that often does not catch every aspect of your sound, it is always good to keep what you made in some audio-way. Try sampling it in all its varieties, with your favorite settings and or knob-twists.

Okay... you now have the sound , but not the list of modules that were used to make that sound.
Doepfer came up with the nice idea of patch-sheets in the last page of every module's manual.
You can print out these modules, stick them on a bigger sheet (i've even seen some on pinboards) and draw in your knob-settings and patchcables.
The idea is/was nice, but i hardly ever used these sheets. But it can be handy for some...

I also like the online Eurorack Modular Synth Planner. With hundreds of modules from 52 different manufacturers (!) you will be able to configure your patch including a variety of colored patch-cables and save it as a screenshot.
This great site is regularly updated with the latest eurorack modules, but still has a few (small) bugs and imperfections. Follow them on Twitter to get their latest updates.
Another online planner is Stefan Breitenfeld's Modular Planner, also very neat but with much less manufacturers/modules.

My personal favorite way to store my favorite patches is the modern way.
Thanks to my smartphone i always have a digital camera in my pocket.
One or two quick snapshots of my patches is often enough, and only takes a few seconds.

LFO's A-145 and A-147

Low Frequency Oscillators or LFO's produce periodic control voltages that can be used as a modulation source for all kinds of other modules.

The A-145 LFO1 was the first and one the most basic single Low Frequency Oscillators that Doepfer sold.
It provides 5 different waveforms; sine,sawtooth, triangle, pulse and inverted sawtooth ,and each waveform has their individual (and simultaneous) output.
With the Frequency-knob and the 3-way switch you can select a wide range of frequencies, from on cycle every minute up to audio frequency at the highest.
A reset input allows you to synchronize the LFO signal to an external trigger signal and each trigger will re-start the waveform from its zero-point.

The most obvious use for an LFO is to do some pitch modulation on a VCO to create a vibrato and to modulate amplifiers (VCA's) for a tremolo effect, but with a creative mind you can use these two modules for all kinds of sound manipulating.

The A-147 Voltage Controlled LFO is basically the same LFO as the A-145.
It doesn't have one of the A-145's sawtooth waves, but does have an extra Control Voltage input that is very useful.
Think of an A-174-2 Wheels Module or A-174-1 Joystick Controller as the most used control voltages, but dare to think further... how about controlling the A-147 frequency with noise or perhaps another LFO for example?
My personal favorite use is to put a voltage of an A-198 Ribbon Controller or Theremin Voltage though the CV input and send it to an VCA to get a tremolo effect, but at a higher frequency in the higher notes.

I will discuss the A-146 LFO2 in a future post because it is a slightly different module with different features and uses.

Booktip VIII - History of House by Chris Kempster

History of House is a very interesting book about the history of House music and the technology behind it.
The book is compiled and edited by Chris Kempster in 1996,  the articles come from music-technology-magazines like 'the Mix', 'Music Technology' and  'Electronics and Music Maker' (E&MM)

The 206-paged book is divided into three parts; The Artists USA, The Artists UK & Europe and a third part that is called 'The Technology'

The first part contains interviews with some of the most influential house-deejays/producers like Marshall Jefferson, Lil'Louis, Larry Heard, Juan Atkins, Derrick May, Kevin Saunderson, Richie Hawtin and Carl Craig.
The interviews that the author/ compiler picked are very well written, and besides giving an insight into the history of house music, they also contain a lot of tech and synthesizer references. Most producers explain what instruments they used and why.
The second part of the book features UK and European artists Kraftwerk, M/A/R/R/S, S-Express, Baby Ford, 808 State, A Guy called Gerald, The Orb and Goldie.

The third and last part is all about the classic House-instruments and probably the most interesting for the readers of this blog.
Here you can find some  interesting articles about the classic house drum machines like the TR-808 and TR-909, the Roland TB-303 acid bassline, SH-101 and Juno 106 synthesizers, the Alesis MMT-8 and Korg SQD1 sequencers and from more modern machines like the Ensoniq Mirage, Yamaha DX100 to the Akai S-1000 and Kurzweil K2000 samplers.

Overall this is a very entertaining book for anyone who is interested in house music, the (mid-)80's synthesizer history and/or its instruments.  8/10

Sanctuary Publishing, Limited, 1996
ISBN: 1-86074-134-7

A-170 Dual Slew Limiter

I mentioned my A-170 Dual Slew Limiter earlier in a few BFF posts, but so far i never took the time to write a separate blogpost about it. Until now that is...

The A-170 Dual Slew Limiter consists of  two separate slew limiters, also known as portamento controllers or integrators.
In electronics, the slew rate represents the maximum rate of change of a signal at any point in a circuit. Just like a Glide circuitry, it flattens or smoothes the incoming signal.

The top section of the module is the 'simplest' of the two Slew Limiters, with one joint control, which sets both rise and fall times (from approx. 0 ...10 sec).

For precision voltage control this one is recommended, but version One (before May 2009 / check your version number on the module's PCB) had a small voltage drop that was caused by the protection resistor at the A-170 output.

( check Doepfer's solutions for that HERE ) 

A-170 modules after May 2009 don't have this voltage loss.

The second Slew Limiter has separate controls for rise and fall times, and you can set the overall range (high/low/medium) for these parameters with a three-position switch. 

Because the diodes in the lower Slew Limiter are voltage-dependant, there is a voltage off-set of around 0.5 V.  This naturally makes it unsuitable for precise 1Volt- per-octave work, but for simple voltage control this is no problem at all.

Not only is the lower Slew Generator suitable for pitch-CV's, you can alternatively use this one as a simple AR (attack/release) envelope generator (works with any gate/trigger or LFO).
Very useful if you don't have enough envelope generators and want some punchy or percussive basslines.

Also worth reading: Wikipedia Current Limiting

Quotes VIII : Karlheinz Stockhausen

" ...being quiet and meditating on sound is something completely different and will be discovered very soon by a lot of people who feel that the visual world doesn't reach their soul anymore. "

Karlheinz Stockhausen - Composer
( 22 August 1928 – 5 December 2007 )

DIY A-180 2 x 4 Multiples Module

Unwired DIY A-180

Okay... Maybe not my smartest DIY-project, but at least i tried;
In one of my earlier posts about Doepfer's pre-punched blindplates i stated that you can easily make your own A-180 Multiples module, and save yourself a little bit of money by making your own.

That last thing is correct; it does save you some money (even a bit more if you shop around for components), but if you count the time putting the parts together you can ask yourself if it was also worth your precious time.

I did order a few of the 4HP width blindplates (punched for 8 socket / identical to A-180 front panel but without printing) and also ordered a bunch of sockets from Doepfer and just had to give it a try.

Mounting the jack sockets was simple though the pre-punched holes. Because i wanted it to be a 2 x 4 multiple i thought it would be smart to turn the both sets of 4 multiples in a different way for easy wiring and a certain balance. (but not really necessary)
The wiring was a bit harder. it's not easy to solder very short wires, especially for a beginner like me. It took ages for me to solder all the sockets together, but i finally got it together and the end result works fine. Be sure you leave no exposed wires on the back, a passive module like the A-180 cannot cause lot of electrical damage but can cause audio or CV 'leakage'.

But... was it worth the 10 Euro's that i  saved by buying the loose components?
For me it just wasn't, but i can image with even cheaper components and connectors or a piece of breadboard instead of soldered wires it might work for you.
Because i still have another pre-punched A-180 blindpanel i will also make the other one.

Not only to work on my soldering skills, but in my opinion you never have enough multiples.

The A-180 front panel without printing is available as a spare part. It can also be used for other DIY modules, for example as a connection unit for other modules that have to be controlled by the universal vactrol module A-101-9 .

Most Wanted - Future Modules Update

It is always good to keep an eye on the posts from the Doepfer Yahoo Usergroup.
Not only to get answer to all the A-100 questions you have, the DIY-tips, and the interesting module discussions but also for Dieter Doepfer's own input, troubleshooting and the occasional company updates.
In one of his latest posts he announced a few interesting 'new' things on Doepfer's to-do list, including a few that are not yet on Doepfer's Future Module page.

The ones you can already find on that page are the A-190-5 polyphonic USB/Midi-to-CV/Gate interface, the A-142-4 Quad Decay, A-195-1 Pitch-to-CV/Midi/USB interface, A-192-2 CV/Gate to Midi interface, A-143-4 Quad VCO/VCLFO and the A-100 touch keyboard.

The original A-126(-1)

I already blogged about the forthcoming A-157 Trigger Sequencer (not much info on the Doepfer site, only in a NAMM 2010 brochure), but the update of the A-126 module was new for me.
The A-126-2 Frequency Shifter II will be a redesign of the old module. 

Because of availability of the special circuit CEM3382 used in the original module's internal quadrature VCO, the 'original' A-126 is no longer available and they had to stop the production of this module. 

It looks like Doepfer is now working hard on a succeeding model without an internal VCO.

Other modules that were mentioned were a VC Slope Generator ( no specs or further info available, but maybe something like the Serge Universal Slope Generator ?- i'm only guessing !), a Master Clock module/synced LFO, the A-100 bus board V2 with some Analoge Systems connectors ( no more Analogue Systems-to-Doepfer adaptors necessary? ), and an A-100 miniature power supply redesign 

Besides that, Dieter posted that they are also still working on various non-A-100 Doepfer products like the Dark Matter (Dark Energy expander with Noise, S&H, a second VCO, Multimode-VCF, additional waveforms and maybe some other effects), the Dark Link, and an expansion board for the DIY Synth. 

" ... still on our to-do list. But I can't say in which sequence the planned products will be released."

Note: Please don't call or mail them too often at Doepfer about release-dates or updates of future modules. The Doepfer website is updated very regularly, so you will find all the latest info there...

Using the A-100 for Sound Processing

A-119 External Input /
Envelope Follower

The A-119 External Input / Envelope Follower module allows you to integrate any audio signal (electric guitar, microphone, midi sound module, computer sound card, CD player, tape-recorder ...) into your A-100 system.

Audio inputs of audio-processing A-100 modules (e.g. filter, VCA, phaser, flanger, waveform processor, distortion, wave multiplier, ring modulator, frequency shifter, spring reverb, panning ...) all require line level signals of around 1Vss. , and if the signal source does not have the required level an external pre-amplifier like the A-119 is recommended. 

This module consists of a (pre-)amplifier, an envelope follower and a comparator.

The pre-amp has 2 inputs, one unbalanced (Asymmetric) for line level signals, and a balanced (6.3mm jack /Symmetric) input for inserting low level signals, like microphones or electric guitars.
The module provides two simultaneous audio outputs of the amplified signal.

The envelope follower 'reads' an incoming audio-signal and sends out a proportional voltage as an envelope to its own output.
The brightness of the LED indicates the envelope output level, which is very useful...

The voltage at the output signal can be used to control the filter frequency, loudness or any other voltage controlled parameters such as filter resonance, LFO speed, clipping level, wave multiples, frequency shift, phase shift, delay time and more...

The comparator generates Gate signals out of the incoming signal.

Whenever the audio input exceeds a certain (adjustable) level, a Gate-signal is produced.

This signal can again be used to trigger various other external modules like envelope generators or even voltage controlled switching.

Again, this is a very useful module that i cannot do without anymore because i often use external audio inputs. Most of the times i have a microphone plugged in for vocoder use or for filtering pleasures, but i have used it with my guitar and other audio too.
I do find it a bit strange that it is not included in one of Doepfer's pre-configured basic systems, for me it was a must-have.