Here's FXDB's interview with Jon Blackstone of Blackstone Appliances:
I started Blackstone Appliances in 1998, but the Blackstone Mosfet Overdrive evolved from something I first attempted to build in the late 70s. I had heard that MOSFET transistors had tube-like characteristics. Then I saw an article in an electronics magazine about how to use MOSFETs, and I tried to make something based on one of the examples in the article. It sounded so-so. I set it aside, and continued to get my distortion by cascading preamps in my modified silverface Twin, or running a Deluxe Reverb into a dummy load. I was a total gotta-be-tubes guy then, and I really didn't know squat about solid state electronics. But from time to time I would dig that old project out, and one day while I was trying something I thought would reduce noise, I started getting lots of second and third harmonics, and a nice, smooth transition from clean to dirty. It was similar to what I was getting with the Deluxe, but with the MOSFETs I could get more of it, and it was easier to control.
In the 80s and 90s I boned up on solid state electronics. Turns out, it actually doesn't hurt to know what the heck you're doing. I never went to engineering school, but you can learn a lot from books, and the engineers hanging out on the newsgroups in the early days of the internet were really helpful. I was doing a lot of modding on a 50-watt Marshall, but I kept futzing with the solid state circuit, too. By the mid 90s, I was running my amp clean, and getting all the distortion from the project circuit. I had it in a big weird chassis, with presets that I changed with a control voltage sent from the guitar. I was never a pedal guy. I've never had a pedalboard in my life.
In 1998, I thought I'd explore offering my distortion circuit as a pedal. I got a table at the guitar show they used to do here in New York, and set up a headphone thing where people could A-B my prototype against any pedal they brought by, or against a cranked Marshall I had driving a dummy load. I just wanted to see if people liked it, but a lot of people wanted to BUY it. So I took pre-orders, and I was in business.
The Mosfet Overdrive is not a boost pedal. It's meant to do all the distortion itself, into a clean amp. Here in New York, you're always playing through somebody else's amp. We ride the subway. We carry our rigs in our gig bags. Of course, a lot of my customers do get additional break-up in the amp, but usually they're mixing the colors of the two, not using the pedal to simply kick the amp harder.
Electronically, my circuit is different because it has four stages that contribute distortion, while most pedals have one. You need that complexity, not just to soften the transfer function, but also to rotate the signal a bit before each time you squash it, and to have different things going on at different points in the decay of the note. And the input stage is unconventional, which is why it cleans up from the guitar controls so much.
I'm not really into copying or tweaking classic circuits. Most boutique overdrives or distortions are based on the Tubescreamer or the Rat. As great as those classics are, I think a lot of people want something else, and minor tweaks aren't going to change the basic character of those circuits.
There are three basic technologies for crafting guitar tone. Tube amp designers stick with the familiar, which is understandable. Digital is promising, but I'm not drawn to it because I don't want to rely on a microprocessor, and I believe there are inherent shortcomings in A-to-D conversion of undistorted guitar signals. What's cool about analog solid state is that there's a lot of freedom to innovate, and you wind up with something that can run on a battery.
Which of your pedals is the most popular?
I just make one thing. I have some other things kicking around that I may put into production at some point, but I think people like that I'm a specialist.
Who uses your pedals and for which genres?
Billy Gibbons really took a shine to the Blackstone Mosfet Overdrive some years ago, and has been buying a lot of them from me ever since. I've done some special versions of it tailored to his tastes. Billy and I have a lot in common in terms of our appreciation for vintage industrial design. When he comes through New York, we usually get together and talk about gear over food and drink. (Or talk about food and drink over gear). Lately, we've been cooking up some ideas for a signature model. It's such an honor that he'd come to me for this, because he's not only a major rock star and an influential guitarist, he's also a serious connoisseur of design and custom gear.