The Source Audio Spectrum Intelligent Filter is an envelope filter pedal that, according to Source Audio, "marries the legendary tones of vintage envelope filter pedals with modern ingenuity"1. Unveiled at Winter NAMM 2019, it was pitched as more than a filter: MusicRadar described it as an all-in-one pedal that "opens up synth sounds, envelope filtering, octave and harmonizer effects"2. It works with both guitars and basses2.
The pedal is built for players who want vintage envelope filter character plus deep editing. On the surface it is a simple four-knob stompbox, but underneath it connects to Source Audio's free Neuro software (Mac and Windows) and Neuro Mobile App (iOS and Android) for editing far beyond what the knobs show1.
What it does
The Spectrum covers envelope filtering, synth, octave and harmonizer effects in one box2. Source Audio says you can "choose from a huge collection of filters including several types of low-pass, band pass, multi-pole, and phaser effects," 25 filters in all1. Guitar World, reporting on the Neuro editing tools, counted 29 different filter options there5.
The onboard presets lean in two directions. Guitar World described them as ranging "from vintage sounds inspired by the Mu-Tron and Lovetone Meatball pedals to contemporary envelopes that incorporate phaser-filtering, distortion and the OC-2 style octave effects"5. Guitar.com's Daniel Ong similarly noted presets "which range from Mu-Tron- and Lovetone Meatball-inspired presets to contemporary favourites that offer distorted octave, phaser and synth-like sounds"3.
The controls
The pedal keeps its playing surface simple. MusicRadar listed the controls at the NAMM unveiling: "Controls include Depth, Speed, Frequency and Mix"2.
| Control | What it does |
|---|---|
| Depth | Sets the intensity of the filter sweep2 |
| Speed | Sets the speed of the effect's response2 |
| Frequency | Sets where the filter sits in the frequency range2 |
| Mix | Blends the effect with your dry signal2 |
Guitar.com described this as "an easy-to-use four-knob control system. The latter allows you to adjust up to eight parameters via an ALT (alternate) switch"3. So each knob has a second function reached through the ALT switch, doubling what the front panel can reach without opening the editor.
A mini toggle switch offers a choice between 'Tron', 'Dumpling' and 'Crier' voicings2. It is also this toggle that cycles the six presets accessible directly on the pedal, with the full 128 available via MIDI1.
Presets, MIDI and stereo
The Spectrum holds 128 presets in memory: 6 accessible via the pedal's toggle switch and 128 available via MIDI1. Source Audio specifies that you can "save up to 128 effect presets recallable with MIDI PC messages via Mini USB"1. The same Mini USB connection is how the pedal talks to the Neuro software and mobile app for deep editing1.
It runs in stereo. Gearnews noted at NAMM 2019 that "it has twin inputs/outputs as well"4, and Source Audio's Neuro 3 Editor adds panning controls "to route each Voice to any location in a full stereo spread"1.
The pedal's bypass is selectable. Source Audio's Universal Bypass lets you choose between high-quality signal relays for true bypass and transparent buffers for analog bypass, so you can match it to the rest of your board rather than being locked into one scheme1.
First of the C4 Synth pedals
At Winter NAMM 2019, Source Audio positioned the Spectrum as the start of a family. Gearnews reported that "the Spectrum Intelligent Filter will be the first in a new line of C4 Synth pedals according to Source Audio"4, and MusicRadar confirmed Source Audio's own framing: "Source Audio says it will be the first in a new line of C4 Synth pedals"2.
The line that followed includes the Source Audio C4 Synth, which Source Audio describes as packing its synth engines "in a compact and easy-to-use effects pedal for guitar or bass"6. Pedal of the Day's review of the C4 Synth counted 25 filter effects in that pedal, the same figure Source Audio gives for the Spectrum's filter collection71.
Release and price
The Spectrum was unveiled at Winter NAMM 20193, with MusicRadar reporting it "will reportedly be ready to ship in Spring"2. Source Audio's current product page lists a sale price of $219.00 as of October 20261.
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Questions
Does the Source Audio Spectrum work with bass?
Yes. When the pedal was unveiled at Winter NAMM 2019, MusicRadar reported that it works with both guitars and basses, and Source Audio's later C4 Synth pedals in the same line are likewise built for guitar or bass. Bass players get the same envelope filter, octave and synth effects as guitarists.
Is the Source Audio Spectrum true bypass?
It uses what Source Audio calls Universal Bypass, which lets you select between high-quality signal relays for true bypass and transparent buffers for analog bypass. So you can run it as true bypass or as a buffered bypass, whichever suits your pedalboard.
How many presets does the Spectrum Intelligent Filter hold?
It has a 128 preset memory. Six presets are accessible directly from the pedal's toggle switch, and the full 128 are available via MIDI, using MIDI PC messages sent over the pedal's Mini USB port.
Can the Spectrum run in stereo?
Yes. The pedal has twin outputs, and Source Audio's Neuro 3 Editor adds panning controls that let you route each Voice to any location in a full stereo spread.
Does the Spectrum use MIDI?
Yes. Up to 128 effect presets can be recalled with MIDI PC messages via the pedal's Mini USB port, which is also how you connect it to the Neuro editing software.
What do the Tron, Dumpling and Crier settings do?
They are three voicings selected by the pedal's mini toggle switch. The onboard presets range from vintage sounds inspired by the Mu-Tron and Lovetone Meatball pedals to contemporary envelopes with phaser filtering, distortion and OC-2 style octave effects, so each voicing points at a different corner of that range.
Sources (7)
- Spectrum Intelligent Filter, Source Audio (sourceaudio.net)
- NAMM 2019: Source Audio's Spectrum Intelligent Filter is an all-in-one synth, filter, octave and harmonizer pedal, MusicRadar, 2019-01-26
- Watch Source Audio’s demo of the Spectrum Intelligent Filter, Guitar.com, 2019-09-10
- NAMM 2019: Source Audio Spectrum Intelligent Filter, gearnews.com, 2019-01-26
- Source Audio's Spectrum Intelligent Filter offers a world of tone-sculpting options, Guitar World, 2019-09-05
- C4 Synth, Source Audio
- Source Audio C4 Synth, Pedal of the Day, 2020-09-15
