The Lumen is an overdrive pedal from Hungry Robot Pedals, and the maker describes it as a State Variable FET-Based Overdrive1. It marks a return to the overdrive world for the company, and it takes an unusual route for the effect type: instead of the diode clipping found in most overdrives, it gets its distortion from cascading FET gain stages, and it puts an active state variable filter, a design more commonly used in synths, inside the overdrive circuit12.
How the circuit works
Hungry Robot is explicit about the design choice behind the gain section. While designing The Lumen, the maker set out to create an overdrive that used no diode clipping, opting instead for "a more natural approach of cascading FET gain stages," with the distortion created by soaking the transistors with gain1. Delicious Audio, reviewing the pedal in April 2020, likewise describes the gain section as comprised of cascading gain stages2.
The other half of the design is the active State Variable Filter. The maker explains that the filter is actually made up of three individual filters, low pass, band pass and high pass, that split the incoming signal into three frequency ranges and amplify them without tone loss1. Delicious Audio describes it as the introduction of a state variable filter, more commonly used in synths, within an overdrive circuit2.
Controls
| Control | What it does |
|---|---|
| Drive | Sets the gain level on the first FET stage1 |
| Clean | Sets the level of the clean blend; past 12 o'clock is boost1 |
| Level | Sets the volume of the drive signal1 |
| Low Pass | Boosts the low pass range of the filter2 |
| Bandpass | Boosts the band pass range, the mids2 |
| High Pass (H.P) | Sets the level of the high pass filter1 |
The three filter knobs only boost. At zero, they leave the signal unaffected, they do not do cutting, as Delicious Audio puts it2. The Clean knob works alongside the drive signal: it allows the original unaffected tone to be reintroduced to bring back some dynamics or to create semi-overdriven tones2.
The maker notes that it is normal for the Drive knob to crackle when turned1.
What reviewers said
Delicious Audio's Paolo De Gregorio, writing in April 2020, called The Lumen "a device that still bears Hungry Robot's trademark quirkiness"2.
Power and size
The Lumen runs on 9V DC with a negative center polarity and a 2.1mm barrel connector, and the enclosure measures 3.7" x 4.7"1. If it leaves you curious about the rest of the maker's drive range, Hungry Robot has also made pedals such as the Mosfet Breaker, the Dual Overdrive and the Mosfet Screamer, and you can read more about the effect type on the Overdrive Pedals page.
Videos
Eirik Stordrange
Eric Merrow
Devon Blue Whitaker (Devon Blue Whitaker music)
Questions
What is a state variable filter in a guitar pedal?
A state variable filter is a filter design more commonly used in synths, as Delicious Audio notes. In The Lumen it is made up of three individual filters, low pass, band pass and high pass, that split the incoming signal into three frequency ranges and amplify them without tone loss, each with its own knob.
Does The Lumen use diode clipping?
No. Hungry Robot states that while designing The Lumen, the goal was to create an overdrive that used no diode clipping. Instead the circuit uses cascading FET gain stages, and the distortion is created by soaking the transistors with gain.
Is it normal for the Drive knob on The Lumen to crackle?
Yes. According to the maker, the Drive knob sets the gain level on the first FET stage, and it is normal for the knob to crackle when turned.
What does the Clean knob do on The Lumen?
The Clean knob sets the level of the clean blend. Past 12 o'clock it acts as a boost. Delicious Audio notes that it lets you reintroduce the original unaffected tone to bring back some dynamics or to create semi-overdriven tones.
What power supply does The Lumen need?
The Lumen runs on 9V DC with a negative center polarity and a 2.1mm barrel connector, according to the maker's product page.
Sources (2)
- The Lumen, Hungry Robot Pedals
- Hungry Robot Pedals: The Lumen, Delicious Audio, 2020-04-23
