If the previous SHAKTI OHM 24- (https://psilobot.vercel.app/rubberv2/index.html) Step Engine was an unyielding, 16-bit algorithmic beat factory, RUBBER OHM v3.6 is its chain-smoking, vintage-obsessed cousin who refuses to write music unless it's routed through magnetic oxide and running at half-speed.Welcome to the RUBBER OHM // MASTER RECORDER PRO, an open-source single-file web application that abandons pattern step-sequencing altogether in favor of raw, elastic audio processing. It takes any loaded audio file and drags it through an analog-modeled tape channel strip equipped with pitch varispeed, a 3-band parametric EQ, delay feedback loops, and dynamic pitch modulation.Here is a deep-dive technical review and architectural reading of this vintage tape emulator.1. Visual & Physical Architecture: Studio Rack AuthenticityInstead of trying to look like a modern DAW plugin, RUBBER OHM presents itself as a heavy-duty, rack-mounted master tape deck.+-------------------------------------------------------------------------------+ | LOAD TAPE // DOUBLE-CLICK FADER TO RESET | +-------------------------------------------------------------------------------+ | [PITCH] [FILTER] [RESO] | [LO EQ] | [MID EQ] | [HI EQ] | [FEEDBACK]| | || || || | || | || | || | || | | || || || | --------- | --------- | --------- | || | | || || || | [SHAKTI R]| [SHAKTI A]| [DELAY MX]| || | | || || || | || | || | || | || | | [1.00x] [OPEN] [0.0] | [5.0Hz] | [0%] | [0%] | [0%] | +-------------------------------------------------------------------------------+ | TAPE DRIVE [TAPE START] [TAP] [120 BPM] [REC VERSION] | | [ slider ] RUBBER_OHM_v3.6 | +-------------------------------------------------------------------------------+ Aesthetic BreakdownChassis: Encased in a brushed dark panel (#1a2426) with a gold border (#d4af37) and subtle radial gradients, evoking 1970s mastering gear.Fader Ergonomics: Features 7 long-throw vertical faders ($300\text{px}$) for high-precision tactile tweaks (Pitch, Filter Cutoff, Resonance, Feedback), paired with 6 split-cell modules for rapid EQ and modulation adjustments.Tactile Quality-of-Life: Every slider supports a native double-click reset (dblclick event listener) to restore hardware defaults—a subtle touch that many commercial Web Audio tools mysteriously forget.2. DSP & Signal Architecture: The Vintage Tape PathLet's dissect the Web Audio graph inside buildEngine(). RUBBER OHM routes signals sequentially through filtering, equalization, non-linear drive, and an integrated feedback delay loop: [ LFO Oscillator ] (Shakti Modulation) │ ▼ (playbackRate Injection) [Audio Buffer Source] ──► [Filter Node] (Biquad Lowpass) │ ▼ [Low Shelf EQ] (250 Hz) │ ▼ [Peaking EQ] (1.0 kHz) │ ▼ [High Shelf EQ] (5.0 kHz) │ ▼ [WaveShaper Node] (Tape Drive) │ ┌─────────────────┴─────────────────┐ │ (Dry Output) │ (Wet Send) ▼ ▼ [Master Summing] ◄────── [Mix Gain] ◄── [Delay Node] │ │ ▲ │ └──┴── [Feedback Gain] ▼ [Master Destination] ──► [MediaRecorder] ──► [.webm Export] 3. Deep Technical Autopsy: The Mechanisms of Wow, Flutter, and Varispeed1. The Varispeed Pitch EngineReal reel-to-reel tape decks do not perform "pitch shifting" using phase vocoders; they simply speed up or slow down the tape motor, linking pitch and time together organically.RUBBER OHM models this by driving the playbackRate property of the AudioBufferSourceNode using semitone calculations:$$\text{Playback Rate} = 2^{\left(\frac{\text{Pitch Semitones}}{12}\right)}$$Sliding the pitch control smoothly speeds up or slows down the entire track, maintaining phase coherent varispeed identically to an Akai or Revox tape machine.2. "Shakti Rate & Amount": Analog Wow & Flutter EngineTo simulate tape drag, capstan slippage, and motor instability (Wow & Flutter), RUBBER OHM directly modulates the sample’s playbackRate using an un-synced LFO oscillator (lfoOsc):JavaScript// Pitch Modulation Setup lfoOsc = audioCtx.createOscillator(); lfoGain = audioCtx.createGain();
// Modulates playback speed directly! lfoGain.connect(source.playbackRate);
// Scaling LFO depth down to prevent pitch destruction lfoGain.gain.value = document.getElementById('lfoAmt').value / 400; By injecting low-frequency sine waves directly into source.playbackRate, it produces cyclic, organic frequency pitch modulation that creates classic vintage cassette wobble.3. Integrated 3-Band Parametric EQ StackThe signal runs through a series of three dedicated BiquadFilterNode instances configured to mimic analog console strip curves:Low Shelf: $250\text{ Hz}$ cutoff ($\pm 15\text{ dB}$)Mid Peaking: $1.2\text{ kHz}$ center frequency ($\pm 15\text{ dB}$)High Shelf: $5.0\text{ kHz}$ cutoff ($\pm 15\text{ dB}$)4. Tap-Tempo Calculated Delay SyncInstead of forcing you to enter millisecond offsets manually, the engine features a built-in Tap Tempo interface. It tracks timestamp deltas between clicks to calculate instant BPM averages and automatically updates the delay node:$$\text{Average Interval (ms)} = \frac{\sum (t_i - t_{i-1})}{N}$$$$\text{Delay Time (seconds)} = \frac{\text{Average Interval}}{1000}$$JavaScript// Updates the Web Audio delay node smoothly without clicking delayNode.delayTime.setTargetAtTime(avgInterval / 1000, audioCtx.currentTime, 0.1); 4. Hardware Emulation vs. Web Code RealitiesHardware SpecReel-to-Reel / Cassette Tape MachineRUBBER OHM v3.6 Web EngineSpeed ControlCapstan Motor Varispeed ($\pm 12$ Semitones)Direct playbackRate Exponential ScalingPitch InstabilityPhysical belt wear & motor jitterLFO-driven playbackRate Modulation (Wow/Flutter)SaturationMagnetic Oxide Tape CompressionNon-Linear Arctan WaveShaper CurveEqualizationSolid-state / Tube Console StripCascaded Biquad Filters (Low/Mid/High Shelf)Echo ProcessingSecondary Tape Head LoopRecirculating DelayNode + GainNode LoopExport MethodMaster Tape BounceInstant In-Browser WebM Stream Recording