CirrusDynamic Overdrive

From the vendor

An updated version of the Tube Screamer featuring a frequency-adjustable midrange boost that can be placed either before or after the drive stage.

Project description

The Cirrus Dynamic Overdrive project is a clone of the Ibanez ST-9 Super Tube Screamer, an incredibly rare Tube Screamer variant only produced from 1983-84. It’s essentially a stock Tube Screamer with an added stage, a semi-parametric midrange control that delivers a fixed boost at a variable frequency.

The ST-9 was introduced near the end of the original run of the 9-series and was quickly discontinued along with the rest of the series. However, the circuit reappeared the next year in 1985 as part of the Master Series, this time called the STL Super Tube. This series had broader distribution and so the STL version is much easier to find.

Curiously, the STL version made one major change to the circuit: transplanting the mid-boost stage after the clipping instead of before, where the original ST-9 put it before. There are no other changes to the circuit, but there is a notable difference between pre-clipping and post-clipping mid boost.

The Cirrus project incorporates both versions, allowing the mid-boost section to be placed either before or after the clipping using an on-board slide switch. (This is the main update from the original 1590B version of the Cirrus, which uses on-board jumpers to set the mid-boost location but can’t be toggled.)

In addition to the mid-boost slide switch, the Cirrus also includes a clipping diode switch so you can select between three different sets of diodes.

Note: This project uses a type of capacitor that has been temporarily discontinued by WIMA. Please see our news article about the issue and the substitution spreadsheet for project-specific recommendations. We are stocking a limited supply in the mean time. The build document has not yet been updated to reflect this.