KautenjaDSP Step Saw User manual

KautenjaDSP

KautenjaDSP Step Saw v2.0.0
Overview
Step Saw is an emulation of the Konami VRC6 sound chip from the Nintendo Entertainment
System (NES). The VRC6 chip contains two pulse wave generators, and a quantized saw wave
generator. Step Saw provides the key features of the VRC6 chip, namely,
•Dual pulse wave generator: Dual pulse waves with 12-bit frequency value and eight duty
cycles: 6.25%,12.5%,18.75%,25%,31.25%,37.5%,43.75%, and 50%
•Quantized saw wave generator: Stepped/quantized saw waveform with retro wave-folding
distortion effect
•4-bit Amplifier: A 4-bit amplifier controls the output level of each oscillator with base/attenuator
knobs and CV inputs
•Channel Mixer: Mix the voices together internally with hard clipping and intentional aliasing
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KautenjaDSP Step Saw v2.0.0
Panel Layout
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1 Frequency
The trimpot controls the coarse frequency of the three waveform generators. Frequency is
quantized to a 12-bit value for the oscillators, which is particularly noticeable in the very low /
high registers. The ports provide an exponential V/Octave input for controlling the pitch of the
tone generators. Inputs are normalled forward from Tone 1, to Tone 2, to Saw.
2 Frequency Modulation
When nothing is patched to the frequency modulation port, the trimpot can be used to fine
tune the frequency of the given waveform generator. When a signal is patched, the input port
provides linear frequency modulation to the corresponding waveform generator and the trimpot
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KautenjaDSP Step Saw v2.0.0
can be used as an attenuverter to attenuate / polarize the incoming signal. Inputs are normalled
forward from Tone 1, to Tone 2, to Saw, and support audio rates.
3 Amplifier
When no input is connected, the trimpot controls the given waveform generator volume level
with 4-bit resolution (i.e., ∈ [0 , 15]). When an input is patched to the port, the trimpot acts like
an attenuator that scales the CV control over the volume level. Because the amplifier has 4-bit
control, the envelope of the voice will sound quantized when used with an external envelope
generator. Inputs are normalled forward from Tone 1, to Tone 2, to Saw. At a volume level of
‘40‘ (≈1PM), the saw waveform general will begin to fold over onto itself and distort. This can
be useful for fat bass-lines.
4 Saw Waveform Hard Sync
An input patched to this port will reset the phase of the saw waveform generator when the
signal crosses a 2Vthreshold. This input supports audio rates.
5 Pulse Width
The trimpot chooses between eight duty cycles: 6 . 25%,12 . 5%,18 . 75%,25%,31 . 25%,37 . 5%,
43 . 75%, and 50%. When an input is patched to the port, the CV controls the offset from the
trimpot’s position. The position of the knob is offset by the CV in increments of 1 V . Inputs are
normalled forward from Tone 1 to Tone 2.
6 Outputs
Each voice produces an output signal of at most 10 Vpp when the amplifier is maxed out. The
individual oscillators cannot be overdriven to produce clipping, distortion, or aliasing
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. However,
outputs are normalled forward into a sum mix where hard clipping can occur. Excess clipping
will introduce an aliasing effect to the mix. Outputs in the mix are clipped before being normalled
to the next output. VU meter lights measure the output of individual channels going from off
( −∞dB to − 12 dB ), to green ( − 12 dB to 0 dB ), and lastly to red (0 dB to 3 dB ) when clipping
begins to occur.
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The saw waveform generator features a built-in wave-folder that does not introduce aliased frequencies when
the amplifier is overdriven.
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KautenjaDSP Step Saw v2.0.0
Data Sheet
Type Oscillator
Size 8 HP Eurorack
Depth NA
Power NA
+12Vdraw (mA) 0 mA
−12Vdraw (mA) 0 mA
+5Vdraw (mA) 0 mA
Sample Rate Programmable
Bit Depth 16-bit
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KautenjaDSP Step Saw v2.0.0
References
Green, S. (2003). NES Sound Emulator (Nes Snd Emu). http://www.slack.net/~ant/libs/.
Horton, K. (1999). VRC6 Chip Info. https://nesdev.com/vrcvi.txt.
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