synthgeek's blog

After posting the PBBPF schematic to the Deathlehem forum, RichardC64 posted an improved schematic which adds small (1k works) resistors to keep the whole signal from being sent to ground, and also adds quick & dirty voltage control using diodes as variable resistors:

From his forum post:

Note that as VR1is reduced, HPCV has less and less effect. On the low pass side, As LPCV increases, there’s less resistance in series with C3, increasing the total capacitance to ground, and thus lowering the LP roll-off. The overall effect of both CVs would be a BP with variable width. Suggested values are R1 & R3 1k-10k, R2 & R4 100k or more, and C3 maybe another 1uF. Trial and Error.

Well, it’s done, and the last bit of experimentation yielded some unexpected results. During my initial tests with using the other side of the second 556, I accidentally found a way to use it as a pseudo-noise generator of sorts. I noticed similar behavior on the APC side at certain settings, but thought it had something to do with the interaction between the oscillator and monostable- apparently it’s possible without the monostable as well.

There are various strange interactions between these new controls and the existing ones- for instance, the new switch not only acts as a pitch drop for the new osc, but also enables the touch points on the first one.  There also seems to be a sort of cross-modulation effect going on (see the audio example further down). All in all, things seem rather unstable with the second module now (certain things seem to make the second half stop working until the power’s cycled, various other strange things happen), which leads me to believe I’ve done something wrong- but it also makes things interesting, so I’m going with it.

Another “happy accident” that happened was that I came accross a nice touch point to make use of the spike- in fact, I found two, so I added a second spike.  I also added some other decorations. Yep, ugly as hell, just like the sounds it makes. :)

Back panel- there are now two outputs for the second module, as well as the output and CV in for the APC:

And now the audio (random touching & twiddling)- first “osc 1″ of the second 556 module (note the sort of AM-type ringing):

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and then “osc 2″:

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This update includes some cosmetic changes, as well as a voltage starve mod (the knob on the top) and a CV input to the oscillator which drives the APC (the silver knob on the “faceplate” controls its level). I’ve decided to name this synth the Mimsy Modular, in honor of the inventor of the Stepped Tone Generator the APC is based on (Forrest M. Mims III), and in reference to my favorite poem (Lewis Carroll’s “Jabberwocky”).

The black stripe is electrical tape, the spike is just something I had in a junk drawer- though it currently serves only as a decoration, it may be used as a touch point in the future. The batteries are now held in place with metal clips which are hot-glued to the box. The metal strip with the voltage starve knob is also held in place with hot glue, and also holds the on/off switch for the APC in place.

Here’s a shot taken during the latest update showing the output of the right-hand module being fed into the APC’s CV input:

And here’s a recording of some knob twiddling with the second module plugged into the CV input, no effects:

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My next plan is to wire up the unused side of the second 556 in a similar fashion as the first, but pitched lower. I will also be trying to find a way to make interesting use of the CV inputs.

A very cool modular softsynth has been released for free by Native Instruments (who Dr. Sync, the developer, now works for). Link:

http://www.syncmodular.com/

Saw this posted at Matrixsynth, so awesome I had to repost:

Saw this in a post at Matrixsynth. My very first keyboard ever was a Casio SK-1, so these kinds of things are always especially interesting to me. This time, however, it’s not actually a circuit bent SK-1, but rather something different based on the chip:

Glitch Labs – Sample Smasher Model 100

WANT!

It seems the main site is not up yet, but the forums have some info.