Mosfet Overdrive


From the Blackstone Appliances website:
Jon Blackstone builds guitar distortion devices that generate low-order harmonics, and are responsive to dynamics. This is the type of distortion that re-shapes the body of the note, instead of coating it with a noisy fizz.

As a guitarist/inventor, Jon has pursued these characteristics for many years, using a variety of technologies including overdriven tube output stages. Interestingly, he has achieved the best results not with tubes, but with small-signal MOSFETs and an unconventional input stage.

Blackstone’s current standard product is a compact battery-powered pedal called the Mosfet Overdrive 2S. It provides two footswitchable channels, each with its own drive and level settings, and true mechanical bypass.

Where the vast majority of overdrive pedals create distortion with a pair of head-to-toe diodes, the Mosfet Overdrive instead utilizes four gain stages, each contributing a small amount of soft clipping. This 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 Blackstone circuit is also unusual in that it interacts with the induc­tance of your guitar’s pickups to get its unique dynamic response. It is very sensitive to playing dynamics, but translates them into changes in waveform distortion, rather than passing them on as changes in output level. This gives you a greater range of expression in your picking technique, but at the same time evens out volume differences. Because the guitar’s pickups and controls are actually part of the input stage, you can get anything from a juicy, harmonic-laden lead sound to a barely-breaking twang with just the guitar’s volume control.

The Mosfet Overdrive is designed to provide these sought-after distortion characteristics entirely on its own. It is not a “boost” pedal meant to cause distortion to occur in your amp. The ideal amp to use with it is the one that best gets the clean sound that you like. The Blackstone will take it from there.


Note that the harmonics generated by the Mosfet Overdrive are more tightly clustered around the fundamental than those produced by a diode-based overdrive at a comparable setting. It also has a nice balance of even and odd harmonics, while the diode-based pedal’s even harmonics barely show up.

No fizz.  Like a good amp, the Mosfet Overdrive imparts harmonics that seem integral to the tone, as opposed to a disconnected fizz. This is not just filtering after the distortion, but a tailoring of each stage to prevent the generation of high-order harmonics in the first place. 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.

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.*

It doesn’t ‘plink’. Many distortion devices tend to over-hype attack transients, giving each note the same “chirp” regardless of what you’re doing with the pick. The Mosfet circuit exhibits a minimum of this tendency. It only spits when you dig in. It emphasizes the body of the note, making it easier to get notes to hang on, but with none of the “auto-pilot” feel of a gain-riding compressor.

The controls on the 2s are slotted-shaft pots flush with the etched steel nameplate on the top of the pedal. They can be easily turned with your thumbnail, yet hold their settings when the pedal is stuffed into a gig bag. The post-distortion EQ control morphs between the original Blackstone voicing and a 10dB mid cut.

At higher drive settings, the Mosfet Overdrive is very sensitive to the differences between pickups. For this reason, 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, so it needs to be the first effect after the guitar. 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. Probably every pedal, preamp or amp out there, no matter how it sounds, is the perfect thing for somebody out there. But if “fizz” or “plinkiness” bothers you, and you want something that inspires expressive playing, check out the Blackstone.

The Blackstone Mosfet Overdrive is built in New York City and sold directly by the maker.

Price: $NFS. Reference Section
Manufacturer: Blackstone Appliances
Color: Black