Modifying the A-124 Wasp Filter for self-oscillation

Out of the box the A-124 Wasp filter can not go into self oscillation, in contrast to most of the other filters in the A-100 system.
Lucky for us modifying the module for self-oscillation is quite easy;
Doepfer's DIY page tells us that;

"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."

Locating the R13 resistor was perhaps the most difficult part of the job. Because the resistors are all soldered on the PCB very tightly it is hard to read what the printing on the board says about the mounted resistors... but i found it!

Locating the R13 resistor

R13 is located in the gap between IC1 (CD4069) and IC2 (i.e. the upper CA3080, close to C4/100pF). See picture above.

I did have a few spare parts lying around, including a 10k resistor. Soldering in parallel in this case was very simple. I did this on the backside of the PCB.

After locating the correct resistor you can simply solder the new resistor on the other side of it. Not much can go wrong.

Just be aware that your soldering-iron doesn't overheat or burn your resistor.

I read mixed reviews of this modification, but you have to remind yourself that the A-124 itself acts kinda unpredictable in the first place, due to the design that "abuses" digital inverters as analog operational amplifiers leading to distortions and other "dirty" effects.

A post-modification audio demo by Madrayken ( Dene Carter ) can be found HERE

 WaspPostMod by Madrayken 

A-175 Dual Voltage Inverter

The A-175 (Dual) Voltage Inverter simply does what the name says; it contains 2 separate inverters that invert the voltage of incoming signals; an input of +4 V will be output as -4 V, an input of -3 V will be output as +3 V, and so on.

Two LEDs give a visual indication of the (positive or negative) output signal for each inverter.

I use this module a lot, as i blogged before, most of the time both inverters are constantly attached to my A-174-1 Joystick module. I am thinking of buying another one soon, because this module is just so useful.

I love the fact that each inverter has 2 inputs, so they can be used as a (mini) multiplier.
In this way you don't have to 'lose' the original signal.

As input source you can use almost any CV source, not just the ones that produce both positive and negative voltages. 

A simple LFO will do, and the Joystick and Modulation Wheels are also very handy basic controllers.

The A-175 manual has some interesting user-examples, including a basic panning patch and a scale/arpeggio-mirroring patch, but again; possibilities are endless, the only limit is your imagination.

Quotes IX : Jean-Michel Jarre

" I think that you have to seriously have fun, or taking serious things in a light way... and obviously for me before all, music is made of fun and pleasure and excitement. "

Jean-Michel Jarre  Composer, musician, artist, producer

(from WikiQuotes)

How To Hide an Arpeggiator

An arpeggiator is a feature available on some synthesizers that automatically steps through a sequence of notes based on an input chord, thus creating an arpeggio.

One of my biggest personal complaints about the 'original' A-190 MIDI-CV Interface was the fact that the front-plate had the text 'arpeg.' on it while an arpeggiator function wasn't even implemented (and still not) in this module.

Doepfer recently stated that "...there were plans to add an arpeggiator when the module was designed about 15 years ago. But we found that the processor power is not sufficient to add this feature..."
He also stated that the new A-190-3 USB/Midi-to-CV module does have an arpeggiator available. ( the A-190-3 is the modular version of the Dark Link and Dark Energy USB/Midi interface, watch an 8-minute video about the Dark Energy's arpeggiator functions below ).

The same functions should work on the A-190-3 ( and Dark Link ) too, but i haven't had any hands-on time with this module to check and haven't seen much info on the web.
It does look like a very basic arpeggiator that will be hard to program, only with external MIDI-controller-messages ( like the R2M if i am correct ), but it is a good start.
I would rather see a more dedicated arpeggiator module from Doepfer, with easy accessible buttons and switches for the different settings and run-modes. Something like the Toppobrillo Quantimator (PDF) or the forthcoming Flame Chord Machine would be nice...

The weird thing though is that the whole arpeggio function is not mentioned anywhere on the module's web-page while this is such a useful function.
In fact; it's the first A-100 module that has a (basic) arpeggiator (!)

Because an A-190-3 manual isn't available yet, you can find a bit more info on how the arpeggiator works in the Dark Link manual ( PDF /page 13)*

*thanks to Paul Rogalinski for the tip

Video: Using Doepfer Dark Energy Arpeggiator

Detailed reference video by Dmitry Shtatnov with Doepfer Dark Energy internal arpeggiator + live song performed using Dark Energy and A-100 modular system.

Black, The New Silver

Like it or not; It looks like Doepfer is slowly changing the main colors of their products into the new black and white color-scheme.
It all started with the Dark Energy synthesizer and the Dark Time sequencer, and recently they changed the case-colors of their USB/MIDI interfaces MSY2, MCV4 and Dark Link.

The first (and probably only) A-100-related new black thing is Doepfer's Ribbon Controller ( The R2M control box and the manual, not the A-198 module itself )
As of June 2011 the cases of this Ribbon Controller will be black with white printing instead of the old silver-grey look.

I like this move towards black from Doepfer because it does make these instruments and boxes look slick(er).
It is probably cheaper too for them to produce, but i'm not sure of that ( and doesn't really matter to me).

But what will be next..? Will they also change the A-100's front-plates?
I guess (and hope) not... that will seriously mess up the overall view in my opinion, although i do like the black and white look from the vintage Moog and Roland modulars.
Fact is that those modules are far better readable due to the high contrast, but i don't think they should apply this to the older A-100 modules. ( but íf Doepfer ever comes up with a range of specific drum-modules i wouldn't mind them being black and white because this can be seen as a separate (sub-) system... )

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...