Describe the process that led to the transition from Boogie’s Mark I to its Mark II amp and the development of the Dual-Mode Preamp.
Let’s back up and describe the Mark I, because it’s such a huge part of the evolution. It introduced cascading high gain to the world—where an extra tube of amplification was added—and that satisfied the main complaint players had in those days. Namely, they had to turn up too loud to get their tone for blues and rock. The cascading high gain of the Mark I provided a new type of amplifier performance tailored specially for lead playing by overdriving the extra preamp tubes. The other important first was that all that high gain could be tamed by a master volume control, and the player could adjust the amount of sustain and distortion apart from the loudness.
You could say the Mark I was the transition piece between the old and the new, because it gave you this high-gain performance by plugging into input 1, and it also provided traditional vintage performance from input 2. But after building the first few hundred—all in my house, mind you—I heard about the desire to footswitch on the fly between the two sounds. So I started including a little A/B switch box and low-capacitance cables so you could toggle the guitar between the two input jacks. For a lot of guys, this worked just fine, but, for others, it forced a compromised setting. So the quest continued. Also, I was surprised by the impact the Mark I had, not only on players, but on other manufacturers, as well, and I was regretting that I hadn’t patented it. [Note: After one year of public sales, it’s too late to file for a patent.] So, I looked for a way to make the Mark I fully footswitchable and patentable. Unfortunately, it wasn’t easy.
What did you do?
Ultimately, I had to re-arrange the sequence of the tube stages, putting the extra gain stage in the middle of the preamp string, and switching it in and out with a little aerospace relay. One of the trickiest problems was getting the reverb to work right in both lead and rhythm modes. The other important element was adding separate master volumes for each mode. Then I went to work on writing the patent. It seems basic now, but in 1978, that Mark II was the first amp that provided two different modes of amplification—one for clean and one for lead. And you could preset individual gain and master controls for each mode and footswitch between them. As such, it was the first “fully modern” amplifier.
What can you tell us about the patent?
The patent title is: “Dual Mode Music Instrument Amplifier,” and it set the stage for all modern footswitching amplifiers. I’ll never forget talking to the retired head of the amplifier division at the Patent Office. He said, “Son, this is one of the best written patents I’ve read, but you’ve got a big problem.” “Uh-oh,” I asked, “What’s that?” And he replied, “It’s going to distort.” Well, we went round and round on that one, and he never did understand that that was the point!
For you legal types, the first part of a patent is called the “Specification,” which I wrote. The second part is the “Claims,” which lawyers write in technical mumbo jumbo. The Claims try to broaden the patented material to anticipate copies with insignificant changes and prevent them from skirting the protection. But Claims that are too broadly written open the door to more prior art and risk invalidating the entire patent. None of the copiers ever denied copying, they all just tried—unsuccessfully—to invalidate the patent.
Any advice for aspiring patent seekers?
If you can write them yourself, they’re not too expensive. Of course, you’ve got to have a unique and potentially valuable idea in the first place, and actually be able to make it into something useful that people really want. We’ve been reasonably aggressive—and quite successful—in using our patents and trademarks to retard the rip-offs, so I think patents, though imperfect, are valuable. The idea is to encourage more invention by granting exclusive use to those who innovate something new. [To see the patent in full detail, check out uspto.com and search for patent number 4,211,893.]