WALDORF MICROWAVE I - The Secrets of Wavetable Synthesis

Waldorf Microwave I is a legendary hybrid synthesizer that combines wavetable synthesis with an analog Curtis filter. This instrument became a key element of electronic music thanks to its unique sound characteristics, which blend digital flexibility with analog warmth.

History of Waldorf Microwave I

Waldorf introduced Microwave I in 1989 as a compact alternative to PPG Wave. While PPG Wave was an icon of wavetable synthesis, its high price and large size made it less accessible. Waldorf aimed to create a rack-mounted synthesizer that would offer the same sound power, but in a smaller and more affordable form factor.

Microwave I was built on an ASIC (application-specific integrated circuit) chip designed by Wolfgang Palm, the creator of wavetable synthesis. This chip enabled fast digital processing of wavetable data, which was then passed through an analog Curtis filter, creating a unique hybrid sound.

Sound Architecture – Digital Power with an Analog Heart

Microwave I is an 8-voice synthesizer that utilizes wavetable oscillators and an analog Curtis filter.

Key Features:

•  Wavetable Oscillators – Ability to switch between various digital waveform cycles.
•  Analog Curtis Filter – A warm, resonant low-pass filter that adds depth and character to the sound.
•  Four Envelopes – Enable precise shaping of amplitude, filter, and modulation.
•  LFO with Multiple Waveforms – Modulates oscillator frequency, filter, and other parameters.
•  Multitimbrality – Allows the eight voices to be split into multiple sound layers.

Thanks to this hybrid combination, Microwave I is extremely flexible, making it an ideal instrument for experimental synthesis.

Wavetable Synthesis Technology in Microwave I

Microwave I builds upon wavetable synthesis, initially developed by Wolfgang Palm for PPG Wave. This approach to sound design combines digital waveforms with analog processing, creating a unique hybrid character that cannot be achieved with traditional subtractive synthesis.

Wavetable synthesis is based on wave tables, which contain sets of digital waveforms. Instead of using fixed oscillators that produce standard sine, saw, or square waves, Microwave I offers interpolation between different waveform cycles. This means that the sound can smoothly transition from one waveform to another, adding liveliness and dynamics.

Digital Oscillators and Waveform Interpolation

Each wavetable oscillator in Microwave I can dynamically change sound by shifting within the wavetable table. This interpolation technique enables complex sound transitions, essential for ambient, digitally expressive tones and dynamic filtering.

This allows for:

•  Real-time harmonic changes, where the oscillator smoothly transitions from a simple sine
   wave to an aggressive digital spectrum.
•  Pitch transformations via LFO speed, creating vibrant pulsating textures ideal for experimental
   music.
•  Percussive effects, where rapid shifting within the table produces metallic, bell-like, and
   synthetic tones.

Structure of Wavetable Tables in Waldorf Microwave I

Waldorf Microwave I features internal wavetable tables, which are a key component of its unique hybrid synthesis. These tables are derived from PPG Wave 2.3 but have an optimized structure, designed for the ASIC chip, ensuring precise interpolation between waveforms.

Table Count and Characteristics:

•  Number of Tables – Microwave I includes 32 original wavetable sets, adapted from PPG Wave
   but optimized for its architecture.
•  Waveform Count – Each table contains 64 individual waveforms, allowing smooth transitions
   via interpolation.
•  Sampling Frequency – The synthesis operates at 250 kHz, providing smoother interpolation than
   PPG Wave 2.3.
•  Digital Structure – Wavetables are created using 16-bit samples, ensuring a rich harmonic spectrum.
•  Table Modulation – LFOs, envelopes, and external MIDI control allow live movement within tables,
   resulting in dynamic sound evolution.

The Curtis Filter – Key to Analog Depth

What sets Microwave I apart from other wavetable synthesizers is its fully analog Curtis filter, which adds warmth and natural character to its sound. Many purely digital synthesizers suffer from a cold and sterile sound, but here, analog resonance and saturation compensate for the digital structure of the oscillators.

The Curtis filter not only functions as a standard low-pass filter but also self-oscillates, allowing for subharmonic resonance, enriching the wavetable sound with analog warmth and punch.

Examples:

•  Low resonance – A smooth sound with subtle saturation, ideal for blending digital oscillators
   into a mix.
•  Medium resonance – Highlights harmonic components, adding liveliness and dynamic motion
   to the sound.
•  High resonance – Produces aggressive and punchy analog waves, contrasting with the digital
   character of the oscillators.

The Curtis filter was also used in iconic synthesizers such as Sequential Circuits Prophet-5 and Oberheim Xpander, confirming its legendary status in analog synthesis.

Stereoping Synth Programmer – Expanding Editing Possibilities

Microwave I was originally designed as a rack-mounted synthesizer, which meant limited direct control over parameters. However, the German company Stereoping developed the Stereoping Synth Programmer Microwave Edition, an external controller that allows direct access to the synthesizer's parameters.

With later firmware updates, this programmer even enables user editing of wavetable tables, allowing musicians to create custom digital waveforms and thus expand the sound design possibilities of Microwave I.

Waldorf Microwave I vs. PPG Wave 2.3 – Detailed Comparison

Waldorf Microwave I is the direct technological successor to PPG Wave 2.3, preserving its wavetable synthesis while introducing modern MIDI integration and a more compact rack format. However, there are fundamental differences between these synthesizers that influence their sound characteristics and control approach.

Key Differences Between PPG Wave 2.3 and Microwave I

Filter – Analog Character

•  PPG Wave 2.3 uses SSM2044, giving it a distinct analog tone.
•  Microwave I is equipped with Curtis CEM3389, which is warmer and less aggressive
   than SSM2044.

Sound Clarity – Digital Interpolation

•  PPG Wave 2.3 has aliasing in higher frequencies, giving it a raw digital character.
•  Microwave I features cleaner interpolation between waveforms, ensuring smoother
   sound transitions.

Control – Rack vs. Keyboard Synthesizer

•  PPG Wave 2.3 has built-in control elements, allowing direct parameter access.
•  Microwave I is a rack module, requiring an external programmer for convenient editing.

MIDI Support – Modern Integration

•  Microwave I has full MIDI compatibility, allowing seamless integration into modern studio setups.
•  PPG Wave 2.3 has limited MIDI functionality, making DAW and sequencer integration
   more challenging.

Differences Between Wavetables in Waldorf Microwave I and Access Virus

Waldorf Microwave I and Access Virus (A, B, C, TI, etc.) take different approaches to wavetable synthesis. However, it is true that some development concepts were transferred from Waldorf to Access, leading to an increase in spectral oscillator capabilities across newer Virus models.

Key Differences Between Microwave I and Virus

Classic Wavetable Synthesis vs. Spectral Shaping

•  Microwave I utilizes true interpolation between waveforms, enabling smooth transitions between
   individual forms.
•  Access Virus employs spectral shaping, where LFO Shape can modulate spectral waveform
   characteristics, though it is not a classic interpolation system like Microwave I.

Number of Tables and Expansion

•  Waldorf Microwave I features 32 fixed wavetable tables, derived from PPG Wave 2.3. Each
   table contains 64 individual waveforms with smooth interpolation.
•  Access Virus A has 16 spectral waveforms, which do not allow classic interpolation but provide
   basic spectral shaping.
•  Access Virus B includes 64 spectral waveforms, significantly expanding synthesis capabilities.
   However, these are not classic wavetable tables, but defined spectral oscillators with
   shaping functions.
•  Access Virus TI contains 80 spectral waveforms, introducing new spectral oscillator types,
   including Grain Table, Formant Table, and Wavetable PWM, enabling advanced sound
   manipulation.

Table Manipulation Capabilities

•  Waldorf Microwave I offers smooth interpolation between individual waveforms within
   wavetable tables, ensuring organic and dynamic sound movement. Each table contains 64
   waveforms, which can continuously transition using LFOs, envelopes, or manual control.
•  Access Virus A, B, C, and TI feature spectral oscillators, which allow shaping and
   waveform modification, but do not use classic interpolation between waveforms like Microwave I.
   For example, Virus TI provides 80 spectral waveforms, which can be modulated via
   LFO Shape and other parameters, altering their harmonic structure.
•  Virus Hypersaw Oscillators generate rich layers of sound by syncing multiple oscillators into
   one signal. However, this type of oscillation does not support classic waveform interpolation
   but rather expands spectral content.

Why Is Waldorf Microwave I Still Sought After?

Despite being released over 30 years ago, Waldorf Microwave I remains one of the most sought-after hybrid synthesizers due to its unique blend of digital wavetable synthesis and the analog Curtis filter.

Key Reasons for Its Popularity:

•  Authentic Hybrid Sound – Combining digital oscillators with an analog filter.
•  Wavetable Table Editing – Thanks to Stereoping Synth Programmer, users can create
   their own waveforms.
•  Multitimbrality – Enables layering of sounds for complex arrangements.
•  Compact Rack Format – Easily integrates into modern studio setups.

Waldorf Microwave I is an excellent choice for musicians seeking a unique hybrid synthesizer with analog character.

Who Used Waldorf Microwave I in Their Productions?

Waldorf Microwave I was a favorite instrument among many renowned musicians and producers, who utilized its hybrid wavetable synthesis and Curtis analog filter for unique sound experiments.

Notable users include:

•  Aphex Twin – Used Microwave I for complex digital textures and experimental sounds.
•  Nine Inch Nails – Trent Reznor leveraged its aggressive digital waveforms combined with an
   analog filter for dark industrial tones.
•  Underworld – Applied Microwave I for deep bass lines and synthetic atmospheres.
•  The Prodigy – Liam Howlett integrated Microwave I into his setup for raw electronic frequencies.
•  Depeche Mode – Alan Wilder used Microwave I for synthetic textures and modulated sounds
   in production.
•  Orbital – The Hartnoll brothers utilized Microwave I for complex sequences and digital
   oscillator filtering.
•  Boards of Canada – Applied Microwave I for organic digital sounds with analog warmth.
•  Jean-Michel Jarre – Experimented with Microwave I in electronic ambient compositions.
•  Autechre – Used Microwave I for complex algorithmic sounds and experimental synthesis.

Conclusion

Waldorf Microwave I is a timeless hybrid synthesizer that has retained its relevance even decades after its release. Thanks to wavetable synthesis, the Curtis analog filter, and the ability to edit wavetable tables, it remains a popular tool among musicians and producers.

If you’re looking for a hybrid synthesizer that offers authentic vintage sound with modern flexibility, Waldorf Microwave I is one of the best choices available.