The retrofit of my PAiA 9720 Dual Oscillator / Modulator went really well.  My Moog Unit (MU) style modular synthesizer is growing and the mix of different manufacturer’s brands of components lends to it an eclectic mix of sounds.  While I really love my Synthesizers.com components I’d like to mix up the sounds produced by my modular by integrating modules from a wide variety of manufacturers.  Having started my modular journey by building a PAiA 9700 I definitely wanted to include it in that mix of modules.

At first I integrated the 9700 with crossover cables.  The were cables with 1/4″ jacks on one end and 1/8″ jacks on the other end.  I got some really cool sounds.  The PAiA modules are grittier for lack of a better word.  They sound sort of like a handful of dirt was thrown into them giving them a more unpredictable sound and feeling.  Perhaps this is because of the use of 5% resistors throughout rather than the more conventional 1%.  It allows for far more drift from the designed specification.  Whatever it is I liked the result and wanted to integrate the PAiA modules more fully with my modular.

As mentioned earlier this conversion began first with the 9720 Dual Oscillator / Modulator.  This conversion brought the number of oscillators in my system up to five.  Having five oscillators in a system has allowed me to produce some damn cool sounds.  I intend to double it before I’m finished.  I was now left with the 9700K MIDI2CV8 converter, the 9710 VCA / Modulator and the 9730 VCF / Modulator.  The nice thing about the PAiA modules is that most include an Attack / Release (AR) or an Attack, Decay, Sustain, Release (ADSR) modulator (or envelope generator).  This flexibility gives the PAiA modules the capabilities of multiple modules.  While the cramming of features into a single module is more of a Eurorack thing it does sometimes come in handy.  The modulators are normalized on the PAiA modules which mean they are tied into portions of the modules circuitry without the need for patch cables.  This normalization, however can be broken through the insertion of a cable into the modulator’s output.

As with the 9720 module the 9710 and 9730 modules only require a slight modification to  support the Synthesizer.com’s +/- 15 volt power supply.  This modification involves first removing the R1 and R2 resistors and replacing them with straight wire link jumpers.  I just used left over pieces of component clippings for this.  While you can short the resistors by just wiring one end of the resistor to the other there will still be resistance on the circuit as some of the electricity will pass through the resistor so I opted to remove the resistors entirely and add the jumpers.

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R1 & R2 (Lower Right) Resistors Replaced With Jumpers

The second step in the power modification involved replacing the 4-pin power connector with a 6-pin Dotcom compatible connector.  The PAiA modules use +15 volts, Ground, Signal Ground and -15 volts.  To add the new connector I simply cut the existing 4-pin connector wires around mid-point and added my 6-pin connector.  Because the Dotcom power supply only has a single ground connection I soldered the Ground and Signal Ground cables together and then linked them to pin 4 (Ground) of the Dotcom connector.  Remember to remove pin # 2 on the connector you use so that it will mate correctly with the Dotcom power supply connector where pin 2 has been filled in for correct orientation.

I should note that I made and tested these power modifications prior to removing the panels from their original FRAC settings.  This way if for some reason the modules failed to function I far less troubleshooting to do than if I had modified everything at once and then tested.  Once I was satisfied that the modules worked with the Dotcom power supply I continued my modifications.

You may have noticed that I didn’t include the 9700K MIDI2CV8 module in the list of modules to which I made this power conversion.  This is because modifying this particular module is significantly different.  While the 9710, 9720 and 9730 modules sit downstream from the 9700K the 9700K itself is connected to the 12VAC wall-wart power supply and supplies the other modules with power.  In order to make the necessary modifications I referred to the Powering the 9700K MIDI2CV8 document provided by PAiA.  This document can be found here.  In a nutshell the modification involves replacing the power connector, rerouting a capacitor, removing the 7805 voltage regulator as the Dotcom supply has its own +5 volt pin required for IC3 (this reduces the power draw by a factor of 10), routing +5 volts to the board and modifying the existing power switch.  This last step is important as the switch cannot simply be removed. The 9700K requires a reset to get things going.  This reset was automatically accomplished with the switch was flipped to activate the power.  I replaced the switch with a momentary pushbutton switch.

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Note the Routing of the Yellow (+5) Line from the Power Connector

When transferring the 9700K to a new panel I decided to leave the board’s connectors in their original positions.  This meant drilling out the panel so that the board could simply be mounted in place while allowing access to the MIDI IN, MIDI THRU and DIP switches.  The tricky part was the DIP switch hole which is rectangular rather than round.  For this I drilled out small holes inside the rectangular area and filed it into shape.  My result is not perfect but it works ok for me.  Additionally because the functions of the output jacks varies based on the positions of the switches I opted not to screen the panel but rather refer to a cheat sheet for the functions of the jacks.

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Modified PAiA 9700K Mounted In the MU Modular

 

Speaking of panels…. Rather than pay wild fees to have a single panel screened by a printing company as I did with my 9720 I opted to have a silkscreen produced for each the 9710 and 9730 modules.  This worked out both good and bad.  The screens produced by Metro Graphics in British Columbia were excellent, however, my silkscreening ability is still lacking.  The results I got for the panels were acceptable for my own use but I wouldn’t produce them for sale until I’ve worked out the kinks.  Some things I’ve learned include; keep the screen about 1 – 2 millimetres off the panel itself.  Cover the area to be screened with a layer of paint prior to using the squeegee.  Apply EVEN pressure using both hands when using the squeegee.  Press hard.  In addition the acrylic paint that I’m using may not be ideal and I’m still searching for the best paint for the job.  As you’ll see from the photos the screening isn’t great but as I said… it’ll do for my personal use.

Once the power modifications were done and the panels screened and drilled it was time to  transfer the modules.  The biggest cost for the job was the 1/4″ jacks.  These panels have LOTS of jacks.  The 9730 has sixteen jacks and the 9710 has thirteen.  I used Switchcraft 112AX jacks.  These are 3 connector normally closed jacks.  I could have gotten away with 2 connector jacks for many of the connections but I got a better deal buying the jacks in bulk (for this project and several others I’m currently working on).  Two of the jacks are actually stereo jacks used on the 9710 VCA.  I began by connecting the jack’s ground lugs all together.  The PAiA FRAC modules have some funky methods of connecting the jack grounds to the potentiometers.  By linking all the jack grounds together it became much easier to connect the few pot grounds to the jacks then back to the board.

Once that was done I desoldered the flying wires connecting the 1/8″ jacks to the PCBs for each of the boards.  I should note that I did one complete module at a time rather than complicate things by doing the modules simultaneously.  Then I removed the potentiometers from the FRAC panels and separated the boards and panels.  For all but one connection (the Pan knob on the VCA) the potentiometer wires interconnecting one another did not have to be cut.  Only one or two ground wires linking the pots to the 1/8″ jacks had to be cut and these were easily reconnected to the new 1/4″ jacks as the jack grounds were all linked together.

I used the PAiA Illustration Supplement for each module to guide the re-wiring process.  I first connected the required resistors, capacitors and bridge wires to the necessary jacks before attempting to wire the flying wires to the panels.  This made soldering things in place much easier.  I then mounted the potentiometers to ensure everything fit into place nicely.  The next step was to connect and pot grounds to the jacks to ensure everything was grounded correctly.  Finally, following the supplements, I connected the flying wires to their respective sockets.  Once again, as with the 9720 VCO, the wire lengths were sufficiently long that they reached their target jacks without extension or replacement.

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9710 VCA Refitted

I did have to remove each module’s LED and add some flying wires to the PCB so the LEDs could be relocated to accommodate my panel design.  Just for kicks I used blue LEDs for the PAiA modules making it easy to locate them in the dark.

Once done each panel was tested using a bench power supply before connection to the modular’s Dotcom QPS1.  If I made a mistake the bench supply would take the hit rather than my production machine.  Fortunately each module worked perfectly and I installed them into the modular after calibration.

So now my modular has the added bonus of some PAiA modules plus I now have 2 MIDI to CV modules allowing me to run my keyboard to some oscillators and an external iPad based sequencer (I still don’t have a sequencer module) to other oscillators.  I’m very pleased with the result!

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5U 9730 VCF / Modulator
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9710 VCA – Note the Right Side – Apply EVEN pressure when Screening

 

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