The TWA Chemical Z (RZ-01) is a Roy Z signature dual-channel overdrive pedal from TWA (Totally Wycked Audio), designed by Susumu Tamura, the creator of the original Tube Screamer1. TWA describes it as a signature overdrive inspired by the Maxon OD808, OD808X, and APEX808 circuits, and Maxon's own index of Tamura-designed pedals calls it the successor of the Apex808 and OD808X12. It was made in a limited batch of 100 units in the USA, and as of late October 2026 the maker's page lists it as sold out, with limited quantities available1.
What sets it apart from a stock 808-style pedal is a second footswitch. The pedal runs two clipping modes, NORMAL and HOT, selected on the fly, and its circuit is built around a rare op amp TWA calls the "Magic IC"1.
Two modes, one 808 foundation
The Chemical Z keeps the familiar three-knob layout of an 808-style overdrive: DRIVE, TONE, and LEVEL1. Two footswitches control it: BYPASS / ENGAGE, and MODE HOT / NORMAL1.
| Control or switch | What it does |
|---|---|
| DRIVE | Sets the amount of overdrive |
| TONE | Sets the treble roll-off / EQ tilt |
| LEVEL | Sets the output volume |
| BYPASS / ENGAGE footswitch | Turns the effect on and off |
| MODE HOT / NORMAL footswitch | Selects the clipping mode |
NORMAL MODE is described by TWA as standard 808-style overdrive. HOT MODE engages an alternate diode pair for increased gain, output, and a different EQ curve1. Those diodes are now-defunct Panasonic DA2S00100L parts, the same type used in the Maxon OD808X Overdrive Extreme, with more forward voltage than standard diodes1. Delicious Audio adds that the HOT mode's diodes produce more gain, more output, and slightly push the mid lows3.
TWA's spec sheet shows the difference between the two modes in numbers1:
| Spec | HOT mode | NORMAL mode |
|---|---|---|
| Maximum gain | 27 dB @ 2 kHz | 23 dB @ 2 kHz |
| Equivalent input noise | Typical 106 dB / A-wt. | Typical 104 dB / A-wt. |
The HOT channel's higher-forward-voltage diodes also change how the harmonics build. TWA explains that even harmonics are added at lower volume levels than the symmetrical clipping diodes would activate, producing rich integer harmonics4.
The Magic IC and how it differs from a Tube Screamer
The heart of the pedal is what TWA calls the "Magic IC," an op amp the company says was used in the APEX808 and in Tamura-Mod Tube Screamer mods1. Delicious Audio describes it as a rare op amp found in limited runs of the TS8083, and Pedal of the Day says the Chemical Z circuit is based around the "Magic" IC that was only found in limited runs of the best-sounding vintage TS808s5. The maker's page also states the Magic IC gives less compression and a more even frequency response than the typically used JRC4558, the op amp most associated with Tube Screamer-style circuits, along with an increased output level1.
For context on the family it comes from: the Tube Screamer uses a symmetrical clipping stage, as Guitar.com's review of the Boss SD-1 notes in contrasting the two circuits6. The Tamura-Mod TS808, another Tamura design sold by Maxon, houses its circuit in a die-cast zinc chassis rather than die-cast aluminum, which Maxon says has different electrostatic and electromagnetic qualities for lower noise7. The Chemical Z shares its designer and parts of its lineage with those pedals, but TWA positions it as its own circuit, combining elements of the OD808, OD808X, and APEX808, with the APEX808 circuit as the main source of inspiration according to Delicious Audio3.
Pedal of the Day found the pedal holds up in front of a modern high-gain rig, writing that "Chemical-Z has been optimized for use with high-gain amps" and calling it "aggressive yet articulate; edgy yet easy on the ears"5.
"More than just a copy of previous designs, Chemical-Z has been optimized for use with high-gain amps"
Roy Z and the Quad Cortex
The pedal carries the name of Roy Z, the guitarist and producer. TWA says Roy uses the Chemical Z to warm up the sound of his Quad Cortex1. For a player running a modeler or profiler, an analog overdrive in front of the unit is a way to add harmonic content and take the edge off the digital front end, and this pedal is Roy Z's chosen tool for that job.
Power, battery and connections
The Chemical Z runs on a 9V battery or an external 9V DC power supply, drawing a minimum of 5 mA1. Battery life is rated at approximately 70 hours on a standard manganese battery, a Panasonic 6F22, at 25°C / 77°F1, so a player gigging weekly can expect a battery to last a long time, though an external supply removes the question entirely.
The Chemical Z uses Buffered Mechanical Bypass switching, not true bypass1. With a buffer in the bypass path, the pedal stays active in the signal chain even when the effect is off, which suits long pedalboard runs but differs from pedals that hard-wire the dry signal past the circuit.
A limited run
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Questions
Is the TWA Chemical Z true bypass?
No. TWA lists the Chemical Z with Buffered Mechanical Bypass switching, with a BYPASS / ENGAGE footswitch and a second MODE footswitch for HOT / NORMAL. A buffer in the bypass path keeps the signal consistent through long pedalboard chains, unlike a true-bypass pedal that passes the dry signal straight through.
What is the Magic IC in the Chemical Z?
It is a rare op amp that TWA says was used in the Maxon APEX808 and in Tamura-Mod Tube Screamer mods. Delicious Audio describes it as a rare op amp found in limited runs of the TS808, and Pedal of the Day says the Chemical Z circuit is based around it. Susumu Tamura, the original Tube Screamer designer, chose it for this pedal.
How many TWA Chemical Z pedals were made?
TWA states that, like all its pedals, the Chemical Z is manufactured in a limited batch of 100, made in the USA. As of late October 2026 the maker's product page lists it as sold out, with limited quantities available.
How long does a battery last in the Chemical Z?
TWA rates battery life at approximately 70 hours on a standard manganese battery, a Panasonic 6F22, at 25°C / 77°F. The pedal also runs on an external 9V DC supply, drawing a minimum of 5 mA.
How is the Chemical Z different from a Tube Screamer?
TWA says it offers less compression and a more even frequency response than a standard 808, with increased output level. It is built around the Magic IC rather than the typically used JRC4558, and its HOT mode switches in an alternate diode pair for more gain, more output, and a different EQ curve.
Why did Roy Z use the Chemical Z with his Quad Cortex?
According to TWA, Roy Z uses the Chemical Z to warm up the sound of his Quad Cortex. Running an analog overdrive in front of a modeler is a common way to add harmonic content and soften the digital front end, and the Chemical Z is his signature pedal for that job.
Sources (7)
- TWA CHEMICAL Z, Godlyke Distributing, Inc.
- Designed by Susumu Tamura, Godlyke, Inc. (maxonfx.com)
- TWA Chemical Z Dual Overdrive, Delicious Audio, 2024-10-09
- TWA Chemical Z Overdrive, godlyke.com, 2024-06-07
- TWA RZ-01 Chemical Z™ Roy Z Signature Dual Channel Overdrive, Pedal of the Day, 2026-01-10
- Boss SD-1 review, Guitar.com, 2025-04-29
- TAMURA-MOD TS808 Tube Screamer (TS808TM), Godlyke, Inc. (maxonfx.com)
