The Vertex Steel String Clean Drive is an analog overdrive pedal from Vertex Effects that aims to put a Dumble Steel String Singer amplifier on a pedalboard. Vertex says it "faithfully recreates the tonality and feel of the iconic Dumble Steel String Singer amplifier in a stompbox format," and that it was designed alongside the "Real Deal" Dumble Steel String Singer, serial number 0011. Premier Guitar describes it simply as Vertex's take on a Dumble Steel String Singer, billed as a "clean drive"2.
The Steel String Singer it copies is a rare, six-figure clean amp, and the players associated with that sound include Stevie Ray Vaughan, whose Dumble Steel String Singer is the amp the pedal traces back to34. Vertex markets the pedal toward the clean and lead tones of albums like "Texas Flood", "Venus Isle", and "Continuum"1.
What it does to your sound
Vertex positions the Steel String between a boost and an overdrive. The maker describes it as a "100% analog tone tool" that "will do it all from Overdrive, to Fat Boost, to Compression, to EQ shaping and more"1. On the MKII, the gain knob sets where it sits: below 50 percent the pedal acts as more of a clean boost with D-style coloration, and above 50 percent it moves into light overdrive4. In a Sweetwater demo, Vertex's Mason Marangella described gain settings below 1:00 as an "incredibly versatile clean boost, with a Filter control to dial in how much of that D-style midrange shaping your instrument demands," with drive above that and enough gain wide open for heavy drive tones5.
The related Steel String Supreme expands on the same idea with a five-control EQ section, a Clean blend knob, and an EQ footswitch, while the standard Steel String keeps the simpler three-knob layout67.
The controls
The original Steel String is a simple three-knob device: Gain, Filter (tone), and Volume68. The MKII keeps those three and adds a Jazz/Rock toggle48.
| Control | What it does |
|---|---|
| Gain | Sets boost versus drive; below 50% (MKII) it is a clean boost with D-style coloration, above 50% light overdrive4 |
| Filter | Tone control for dialing in D-style midrange shaping5 |
| Volume / Level | Output level84 |
| Jazz/Rock toggle (MKII) | Voices the low-end EQ; Jazz cuts bass about a dB, Rock returns it to stock45 |
The Jazz/Rock toggle came from player feedback. Marangella explained that some players found the D-style sound "so fat it's almost too fat" through small combo amps, so the Jazz position trims the bass5. Delicious Audio notes the toggle mirrors the Jazz and Rock voicing of the original Dumble amps, and that the feature also appears on the Dumble Special Overdrive series86.
Power and bypass
The Steel String runs on 9 to 18VDC center-negative power, with the adapter not included1. Vertex says 18V provides more clean headroom4. There is no battery option in the listed power spec. Switching is true bypass, specified as mechanical true bypass switching on the MKII4. The Slight Return Edition of the pedal draws 20mA9.
The center-negative 9 to 18VDC requirement means the pedal needs a matching power supply, and the higher voltage is the one to use for the cleanest headroom on boost settings14.
History and versions: MKI and MKII
The Steel String Clean Drive was first released in 2016 and marketed as a Dumble-style drive pedal, according to Aion FX, which also notes it was marketed by Vertex as an original circuit but says "once again there was nothing original about it," and that it was "said to be the product of design research against a real Dumble Steel String amp"10. Delicious Audio dates the company's first Steel String pedal to 2017, voiced after serial number 1 of the original amp as a simple three-knob device6.
The MKII arrived in 2020, adding the Jazz/Rock voicing toggle8. It is based on serial number 001 of the 6L6 Dumble Steel String Singer and is 33% smaller than the MKI, with the complete circuit included4. Vertex pitches it as a "sub $200" stompbox4. A gold MKI was a limited edition color with only 200 pieces made11.
The line grew from there. The Steel String Supreme launched in October 2020 with Gain, Level, Output, Fat, Clean, and Filter controls12, and the Steel String Supreme SRV followed with an independent EQ section and five extra tone-shaping controls over the MkII13. A Slight Return Edition single-channel version also carries the serial 001 circuit in a 4.5" x 2.2" x 1.8" steel chassis weighing 1.0 lbs9.
What reviewers said
Premier Guitar reviewed the pedal as a Dumble Steel String Singer take billed as a "clean drive"2. On That Pedal Show, Mick and Dan tried it in 2017 and found "a really interesting low-end and huge push in the low-end," noting it does not have a glassy top end and is "fat bigger"3. The maker's own product page shows a 4.92 rating across 100 reviews1.
A demo video by Shawn Tubbs and a demo by Chris Buck appear on the maker's page, framed as "John Mayer's Dumble In A Box?"1.
In Sweetwater's Supreme demo, Mason Marangella and Ford Thurston described the standard MKII as "the little brother" of the Supreme, "also great but" without the expanded controls, and suggested stacking it with a Tube Screamer-style circuit to reach SRV and John Mayer territory7.
Related Vertex pedals
- Vertex Steel String Drive MkII: the compact second version with the Jazz/Rock toggle
- Vertex Steel String Supreme: the MKII circuit plus a five-control EQ section and EQ footswitch
- Vertex Steel String Supreme SRV: the Supreme circuit styled after Stevie Ray Vaughan's Dumble
- Vertex Ultra-Phonix HRM and Vertex Ultraphonix Special Overdrive MKII: Vertex's Dumble Overdrive Special-inspired drives
- Vertex Tone Secret and Vertex Tone Secret OD: Vertex's Tube Screamer-style overdrives
For more on the category, see overdrive pedals and boost pedals.
Videos
Premier Guitar
Vertex Effects
Vertex Effects
Questions
What does the Jazz/Rock toggle do on the Steel String MKII?
It voices the low-end EQ. In the Jazz position it cuts the bass by about a dB, which Vertex added after players found the D-style sound too fat through small combo amps. In the Rock position the bass returns to the stock setting. It works the same way on the Steel String Supreme.
Can the Vertex Steel String run at 18 volts?
Yes. The pedal runs on 9 to 18VDC center-negative power, with the adapter not included. Vertex says 18V provides more clean headroom, so players who want the cleanest boost setting can benefit from the higher voltage.
Is the Vertex Steel String a clean boost or an overdrive?
Both, depending on the gain setting. Vertex says that below 50 percent gain the MKII acts as a clean boost with D-style coloration, and above 50 percent it moves into light overdrive territory. The maker describes it as usable for overdrive, fat boost, compression, and EQ shaping.
Is the Vertex Steel String true bypass?
Yes. Vertex lists true bypass switching across the Steel String line, with mechanical true bypass switching specified for the MKII. The bypassed signal passes through without the circuit coloring it.
Is the Vertex Steel String Clean Drive based on a Dumble?
Yes. Vertex says the pedal was designed alongside the Dumble Steel String Singer serial number 001, and that it recreates the tonality and feel of that amplifier in a stompbox. Premier Guitar describes it as Vertex's take on a Dumble Steel String Singer.
How many gold Steel String Clean Drives were made?
The gold MKI was a limited edition color with only 200 pieces made, assembled in California. A later MKII run was recalled by a customer review as 1000 units made and ready to ship.
Sources (13)
- Steel String Clean Drive, vertexeffects.com
- Quick Hit: Vertex Effects Steel String Review, Premier Guitar, 2017-10-23
- TPS Pick’N’Mix: Orange Fur Coat, Vertex Steel String, Walrus Audio Julia, Sinvertek FluidTime II, That Pedal Show (youtube.com), 2017-10-03
- Steel String MKII, vertexeffects.com
- Vertex Effects Steel String Drive mk 2 Overdrive Pedal Demo, Sweetwater, 2020-03-14
- Vertex Steel String Supreme, D-Style Drive, Delicious Audio, 2021-09-16
- Vertex Effects Steel String Supreme Demo, Sweetwater, 2020-10-14
- Vertex Steel String Drive MkII, Delicious Audio, 2020-10-14
- Steel String (Slight Return Edition), vertexeffects.com
- Delta Amp Overdrive / Vertex Steel String, Aion FX, 2020-06-05
- Gold Steel String Clean Drive, www.vertexeffects.com
- Vertex Effects Steel String Supreme: Can it get you that John Mayer Continuum tone in a pedal?, gearnews.com, 2020-10-15
- Vertex Effects Steel String Supreme SRV Preamp Pedal Demo, Sweetwater, 2021-11-16
