Intense Tech #01 — LSDj Wave Synth Deep Dive, Part 1 (Defense Mechanism)

The first intense-tech article: defense-mechanism explains the lsdj wave synth's SIGNAL, VOLUME, FILTER, CUTOFF and Q by way of the harmonic series, and shows how to extract a sine wave — the deepest bass the Game Boy can make — from a synth that has no sine setting.

Key claims#

• The wave channel plays "a 4-bit, 32-sample waveform": 32 hex digits 0–F on the Wave screen (the default saw reads 8ECDCCBBAAA999888776665554433231). Sixteen volume levels against 65,536 for 16-bit audio — "part of what gives the Wave channel its characteristically crunchy sound".
• Harmonic series in LSDj note names (version 6 and later; "for version 4, add 1 octave"): A3 220 Hz × 2 = A4 440 (octave), × 3 = E4 660 (octave + fifth), × 4 = A5 880, × 5 = C#5 1100 (two octaves + major third), × 6 = E5 1320. Multiples of 2 are octaves, of 3 fifths (9 = a major tenth), of 5 major thirds; 7 is "kind of an out-of-tune minor 7th", 11 an out-of-tune flat fifth.
• The default SIGNAL is a sawtooth (all harmonics); the LSDj saw at 440 Hz "sounds surprisingly faithful" to a high-resolution one. Square = odd harmonics only (also the pulse channels at 50 %); triangle = odd harmonics falling off faster — "a good sound for a very deep bass" (the NES triangle). There is no sine setting, but every option is built from sines and the FILTER extracts one.
• FILTER: Lowp passes the CUTOFF and below ("up to 15 overtones, in theory"), Highp above, Bandp the range at the cutoff, Allp everything with phase shifts around the cutoff. CUTOFF is 00–FF.
• Sine recipe: lowpass with CUTOFF 10 (16 of 255) keeps only the fundamental — "a wild sine shape appears", a little squashed; Q (resonance) boosts the cutoff: Q 1, then VOLUME 08 with Q 3 is "pretty close to a sine wave". VOLUME scales the signal before filter and Q; set PLAY to MANUAL to hear only the first wave. At low octaves this is "the lowest, bassiest possible sound you can get in the Wave channel", for sub-bass or kicks; the 16 levels let some overtones creep in.
• Every multiple of 10 in CUTOFF is one overtone: Bandpass with VOLUME 20 and CUTOFF 20 sounds the octave, 30 the octave + fifth, 40 two octaves, and so on; raise Q to emphasise it; higher overtones come out quieter, as in a real sawtooth; square and triangle "miss" some.

Practical takeaways#

Read CUTOFF in steps of 10 as harmonic numbers; lowpass 10 + Q + low volume = sine = the sub-bass and kick wave; bandpass at 20, 30, 40 isolates overtones for bell-like or hollow timbres.

Notable quotes#

"By the end of this lesson you'll understand how to make a sine wave."

Pages touched#

wavetable-programming · instrument-design · game-boy-apu · lsdj · intense-tech · defense-mechanism