A lot has changed since Jon Black­stone first offered his “Mosfet Overdrive” circuit as a pedal in 1998. Yet here in 2024, with all the boutique amps, emulators and pedals available, many guitarists continue to rely on it as their go-to dirt box.

People that bond with the Black­stone Mosfet Overdrive are probably looking for the same thing Jon was during the decades he was modding tube amps – harmonics that seem integral to the tone, not a fizz that sits on top of it.

The pedals Jon is cur­rent­ly building are the same ones he's been making for 20 years or so. Two “channels” (foot­switch­able presets), in an MXR-sized pedal with unique recessed controls. They're sold here on this website, not on Reverb or Amazon.

While most overdrive pedals create distortion with a pair of head-to-toe diodes, the Blackstone instead employs four gain stages, each con­tributing a small amount of soft clipping. That avoids intermodula­tion and the creation of fizzy high-order harmonics, just as in the best vintage amps. Those amps sound good in large part because the distor­tion does not occur at just one point.

The cir­cuit is also un­usual in that it interacts with the induc­tance of your guitar's pickups to get its unique dynamic response. Because the guitar's pickups and controls are actually part of the input stage, you can go from a juicy lead sound to a barely-breaking twang with just the guitar's volume control.

The Mosfet Over­drive gets its distor­tion entirely on its own – it is not a "boost" pedal meant to cause distortion in your amp. It does its thing into pretty much any amp, at any volume.
 

3 WAYS IN WHICH THE BLACKSTONE IS DIFFERENT: 

The character changes as the gain increases.  It's glassy at low settings, becoming fat and midrangey when cranked. This is the opposite behavior of most pedals, which get thinner and fizzier at high settings. And this makes it versatile, ranging smoothly from very subtle to pretty heavy.

Control it from your guitar.  Another area where the Blackstone stands out is in how you can control it with the volume control on your guitar. If you listen to the third clip on the sound clips page, you'll hear how most pedals just get a little brighter when the guitar volume is increased from 6 to 10, while the Blackstone runs the gamut from almost clean to a fully saturated sound. The Blackstone must be the first effect after the guitar to acheive this.*
The Mosfet Overdrive ships in its original "reactive" mode. In this mode, it interacts with your pickups, which is the main reason it "cleans up" so much from the guitar's volume control. However, putting other pedals (or wireless systems) between the Blackstone and the guitar will result in thin, harsh tone when the Drive control is maxed out. But now the Blackstone includes a small internal switch that puts it in "buffered" mode. This permits unconditional use after other pedals, at the expense of some of the extraordinary "cleaning up" from the guitar controls.

OK, the controls are weird. It has slotted-shaft pots that are flush with the etched steel nameplate on the top of the pedal. They can be turned easily enough with your thumbnail, but they hold their settings when the pedal is stuffed into a gig bag. The EQ control is not a high cut, it's a post-distortion mid cut.

At higher drive settings, the Mosfet Overdrive is very sensitive to the differences between pickups. That's why the drive control for the "red" channel is divided into two ranges - one which causes single-coil pickups to sound fatter as maximum drive is approached, and one which tightens the bass when humbuckers or P-90s are used. In its standard mode, the circuit interacts with the guitar's pickups, and needs to be the first effect after the guitar. But there is now an internal switch that puts the pedal into "buffered" mode, permitting use after other effects, wireless systems and active pickups.

It's important to remember that recommendations you hear on overdrive pedals often stem from somebody getting a good sound out of a combination of a certain pedal with a certain amp, when a lot of the distortion was actually occurring in the amp. Again, the Blackstone is intended to get the distortion on its own, into whatever amp is suitable (or available!) for the gig you're playing.

Distorting the electric guitar is a very subjective thing. But if you're looking for a tone that's more juicy than fizzy – something that inspires expres­sive playing – you may want to check out the Blackstone. ∎