The Dr. Z Z-Drive is a dual-voice preamp pedal built around two different overdrive circuits: one germanium, one MOSFET. It was made by Dr. Z in collaboration with EarthQuaker Devices, designed by Jamie Stillman, and produced from 2015 through 2023. It is now discontinued123.
The Z-Drive is no longer in production. EarthQuaker Devices' Corey Jenkins and Jamie Stillman explained that the pedal was discontinued because the specific diodes used in the circuit ran out, and "there was no good approximation for them," with any replacement changing the sound too much. Production ran from 2015 through 20233.
What the Z-Drive does
Delicious Audio's Paolo De Gregorio described the concept plainly: "With the Z-Drive you essentially get two pedals in one." A channel footswitch selects between two distinct-sounding preamp channels, configured in A/B fashion, meaning they cannot be stacked1. Guitar Interactive Magazine's Jonathan Graham described the same arrangement in his coverage of the release2.
The two channels sound different by design:
- Green channel (germanium): uses NOS germanium diodes and is a lighter, more open-sounding overdrive, which De Gregorio said "can move from a sparkling clean boost to dynamic, open sounding overdrive"12.
- Red channel (MOSFET): a more compressed, higher-gain overdrive, described by De Gregorio as running "from edge of breakup grit to blistering distortion"12.
The controls: EQ before two gain channels
The signal path places an active three-band EQ section before the two gain stages. Because the signal goes through the EQ first, turning the EQ controls clockwise can increase overall gain and distortion, a point both Delicious Audio and Guitar Interactive Magazine make12. That is worth knowing as a player: the EQ is not a tone cut after the dirt, it shapes what reaches the overdrive circuits, so it changes how hard they clip.
Each channel has the same control set:
| Channel | Circuit | Controls |
|---|---|---|
| Green | Germanium, using NOS germanium diodes | Level, Drive, Cut toggle switch |
| Red | MOSFET | Level, Drive, Cut toggle switch |
Both gain stages use hi-fi OPA 2134 op amps12.
Where it came from
The pedal began with a request from Dr. Z. In an EarthQuaker Devices interview, Jamie Stillman recalled: "Z reached out to me about designing an overdrive pedal specifically for one of his amps. That led to the Dr. Z Z-Drive," which he described as "a Germanium/MOSFET dual-voice preamp"3. The pedal was sold as a Dr. Z product, a collaborative effort involving Stillman, rather than under the EarthQuaker Devices name1.
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Questions
Why was the Dr. Z Z-Drive discontinued?
Corey Jenkins and Jamie Stillman of EarthQuaker Devices explained that the pedal was discontinued because the specific diodes used in the circuit ran out, and there was no good approximation for them: any replacement would have changed the sound too much. The pedal was in production from 2015 through 2023.
Can you stack the two channels on the Z-Drive?
No. The two preamp channels are configured in A/B fashion, meaning they cannot be stacked. The channel footswitch selects between the Green and Red preamp channels rather than running one into the other.
Who designed the Dr. Z Z-Drive?
Jamie Stillman designed the pedal. According to Stillman, Dr. Z reached out to him about designing an overdrive pedal specifically for one of his amps, and that collaboration led to the Z-Drive.
What op amp does the Z-Drive use?
Both gain stages use hi-fi OPA 2134 op amps, as reported by Delicious Audio and Guitar Interactive Magazine.
Is the Z-Drive made by EarthQuaker Devices?
The Z-Drive is a Dr. Z pedal made in collaboration with EarthQuaker Devices. Jamie Stillman of EarthQuaker Devices designed it at Dr. Z's request, and it was sold under the Dr. Z name.
Sources (3)
- Dr. Z Z-Drive (collaborative Pedal With EarthQuaker Devices), Delicious Audio, 2019-05-24
- Dr. Z Releases Z-Drive Overdrive Pedal Designed by Earthquaker Devices, Guitar Interactive Magazine, 2015-08-27
- Pre-Amp Alchemy: A Deep Dive into the ZEQD-Pre with Jamie Stillman, EarthQuaker Devices, 2026-03-12