Synth Workshop Modular Mayhem On the Kurzweil PC3

July 1, 2010

Kurzweil_1_frontOn Kurzweil’s PC3 series synths, a layer of a sound program can have up to four “units” of DSP—measures of how hard the chips work to create sound. You can spend DSP units on a modeled analog oscillator, a filter, or other synthesis building blocks. Thus, the PC3 is sort of like a virtual modular synth, only with DSP emulating modules, and algorithms (signal chains) acting like patch cords.


Things like the Triple Saw oscillator or four-pole filters use all four DSP units of a layer. Cascade Mode gets around this limit by running one layer’s output into another layer’s DSP, with up to 32 layers in series. To illustrate this, we’ll run a Triple Saw oscillator into a series of filters: four-pole lowpass, four-pole highpass, and finally, a sweeping allpass filter for a cool phasing effect. Dave Weiser

 Click images for larger versions, after these online extras.


Step 1: Create the Triple Saw oscillator.

PC3D_2Start with program 1,024: “VAoneNaked- SawMono,” a basic template for virtual analog sounds. Hit Edit, go to the ALG page, and select algorithm 5. Cursor down to the large single DSP “block” and scroll the data wheel until you see “TRIPLE SAW.” This oscillator generates three individual saw waves; one stays in tune while the other two can be detuned for fatness on the DSPMOD page.


PC3D_3This might not make sense initially, but go to the DSPMOD page and turn the level for this layer all the way down to –96dB. Now, we’ll create a layer into which this oscillator can be cascaded. Hit the left “more” soft button until you see a “DupLyr” soft button. Hit this to duplicate the current layer, and you’ll find yourself in Layer 2.



PC3D_4Step 2: Create and set the lowpass filter.

We’ve duplicated our oscillator, but we need this layer to be a filter. Remain in Layer 2 and go to the ALG page. Change algorithm 5 to 105. (Each PC3 algorithm has a Cascade Mode counterpart, referenced by the original algorithm number plus 100.) Below that, select “Layer 1” as the Alternate Input. Now you’re running Layer 1 into Layer 2. (Toggle between layers with the +/- buttons to the left of the display.) Move the cursor down to the DSP block and scroll until you see “4POLE MOGUE LP.”

PC3D_5On Layer 2’s DSPMOD page, set the level at –15dB, filter frequency (LP Frq) to 1,319Hz, and resonance (LP Res) to 7dB. With the cursor on LP Frq, move to the source field at top right (Src1) and select “Data” (slider A on the PC3) as the source—simply hold the Enter button and wiggle the slider. Set the depth to 2,400 cents. You’ll hear the Triple Saw oscillator through the filter, and be able to sweep the filter with slider A.

Step 3: Create and set the highpass filter.
PC3D_6Duplicate Layer 2 the same way you did Layer 1, but first, turn down its level on the DSPMOD page. In Layer 3, go to the Alg page, select Layer 2 as the Alternate Input, and select “4POLE HIPASS W/SEP” as the DSP block type


PC3D_7On the DSPMOD page in Layer 3, set frequency (HP Frq) to 98Hz and resonance (HP Res) to 7dB. Keep slider A (Data) as Source 1 (it’s already there since the layer is a duplicate), but raise its depth to 3,500 cents. When you move slider A, you’re now affecting the highpass and lowpass filters. Raise the Level to –15dB in the bottom left field.


Step 4: Create and set the allpass filter.

PC3D_8Duplicate Layer 3, but this time, don’t turn down its volume. The way an allpass filter works requires that it be mixed with a dry, unfiltered signal. In Layer 4, select algorithm 108 with Layer 3 as the Alternate Input. Make the DSP block “3POLE ALLPASS.”


PC3D_9Next, go to the DSPMOD page. Make AP Frq 988Hz, AP Width 0.400 oct, and AP Sep1 (separation) 2,000 cents. Move the cursor in the left column to the AP Frq row, then on the right, select LFO1 as Source 1 (hit keypad button 0 and scroll backwards—you’ll see LFO1 after a few clicks). Set LFO1’s depth to 2,000 cents. Raise the level for Layers 3 and 4 to –6dB.


Step 5: Add some modulation.

PC3D_10 On the LFO page in Layer 4, set rates of .30Hz minimum and 8.6Hz maximum. Set the shape to “Sine.” To make a slider control the rate, wiggle that slider (I used slider B or MIDI 13) while holding Enter. Varying the rate while playing adds a vibe reminiscent of classic sci-fi or old Parliament albums.
     You now have three detuned saw waves running into a series of three filters, with slider A sweeping the cutoff and slider B controlling the rate of the phasing imparted by the allpass filter. Since we’ve used only four of 32 layers, your “virtual modular” setup can get a lot more complex. Just repeat the basic workflow: Duplicate your layer, decide what “module” that layer will be on that layer’s ALG page, then tweak the “knobs” of the module on the DSPMOD page. Happy programming!

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