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Delta Amp Overdrive

Based On
Vertex® Steel String
Effect Type
JFET Overdrive
Build Difficulty
Project Summary
Jack Orman’s classic mini-boost circuit, using J201 JFETs to achieve an amp-like overdrive tone.
Delta Amp Overdrive printed circuit board

Printed Circuit Board

What's included?
PCB only. Build instructions and parts list can be viewed or downloaded from this page.


In stock

Complete Kit

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Kits are developed based on interest, so if you’d like to see one for this project, let us know.
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Project overview

The Delta Amp Overdrive is an adaptation of the Vertex Steel String Clean Drive, first released in 2016 and marketed as a Dumble-style drive pedal. The name refers to the Steel String Singer, a model of Dumble amplifier).

Aion FX endeavors to be as charitable as possible in talking about commercial companies, but there’s no way around it: Vertex has a history of shady business practices, using slick marketing to make up for a lack of design integrity or originality.

You can find hours worth of reading material on The Gear Page if you want, but briefly: Mason, the owner of Vertex Effects, was caught in a series of lies in 2014 for selling an expensive “boutique” wah pedal that was discovered to be just a rebranded BBE Ben Wah. He confessed, apologized, and promised to be honest going forward. Somehow, people still continued to buy his pedals even after this.

In late 2016 he released the Steel String pedal, said to be the product of design research against a real Dumble Steel String amp. But when it was traced by the DIY community, it was found to be a near-exact copy of Jack Orman’s classic Mini Booster circuit with Aron Nelson’s mods and R.G. Keen’s improved biasing scheme, with a few minor tweaks to the values. It was marketed by Vertex as an original circuit, but once again there was nothing original about it.

So to give credit where credit is due: the Mini Booster is a fantastic JFET-based circuit developed by Jack Orman dates back to the early 1990s, and Aron Nelson had the great idea to add a Big Muff-style tone control to the end of it in 2000. Vertex had zero original ideas, unless you count marketing it and concealing his source without credit.

The Delta Amp Overdrive is a direct adaptation of the Steel String Clean Drive, but with the option to use either through-hole or surface-mount (SMD) JFETs.

Since the J201 is very difficult to find in TO-92 through-hole format, and many DIY hobbyists are intimidated by SMD parts, Aion FX offers J201s in SMD format that have been pre-soldered to adapters so they can be used as through-hole parts.