It's true I've been in a foul mood for quite some time, but I had no reason to take it out on you, therefore I apologize.
I am going to make another long rambling post which I cannot reasonably expect anyone to read, so other than one technical correction to your rebuttal which I shall make first, feel free to skip the rest of the post.
The term of a patent runs from the application date, not the date of issuance. The patent in question has an application date of August 30, 1995, and expires twenty years from that date, not the date of issuance in 1997. If you think briefly about the consequences, you'll see why that is (it used to be 17 years from issue, but it didn't use to take the USPTO three years to issue a patent). Therefore, the patent is fourteen years old, more than two thirds the way through its life.
Long rambling part:
Next, about patents in general. It's true, I have filed for no patents. Thinking back, given that somehow in 2001 a person was granted a patent for balanced guitar wiring, strangely in the great scheme of things I could have also been eligible for a patent. Nevermind that I think his original patent could probably be challenged on grounds of prior art and being obvious. His circuit described in the patent had several shortcomings; I published a circuit that improved those aspects. Now, were I to use a balanced guitar circuit, I would have to license his patent, but anyone using my circuit would have had to license both patents (until his expired first, then just mine, etc.)
Except I had no intention of doing that, because in the natural order knowledge is and wants to be free. So I just published a white paper and declared my elements of the circuit design to be public domain.
That wasn't even that clever of an idea; I've had better ideas but those had clear prior art, so . . . anyway, let's talk the silliness of the modern patent system for a minute. I used to have a friend who is a patent attorney. His biggest client was the parent company of Titlest. He spend a good chunk of his career filing patent applications for golf ball dimple patterns. Are there hundreds of potential golf ball dimple patterns? I imagine. Are there hundreds of useful golf ball dimple patterns? I don't know, but I do know that Titlest doesn't sell hundreds of different golf balls with different dimple patterns.
What does that mean? It means they aren't filing these patents because they believe each new dimple pattern is the best ever. It's a form of corporate mutually assured destruction is what is it.
But I don't accuse our diligent amplifier designer of such foibles. Unlike dimple patterns, he has a single good, workable concept. Unlike the balanced wiring one, I think his is actually a novel idea. I even suspect I would like his amplifier, probably much more than you would. I never claimed his patent was bogus.
But what it is, and solely is, it's a brilliant technical solution to a marketing problem. As I argued before, there are prior art solutions of hybrid design that accomplish these same goals:
- no output transformer
- tolerant of various loads
- open-circuit tolerant
- short-circuit tolerant
- regulated power supplies
The problem is if you put a transistor in the "audio path", it's not a "pure tube amp". He has staked out a marketing position that his arrangement of MOSFETs still comprise a "pure tube amp". But as I and many others have argued, guitarists really do want output transformers and their nonlinearities.
I think hybrid design has a lot of potential, but it has to overcome the "stigma" of being a hybrid design. Let's consider these hybrid designs:
(for purposes of this discussion, each stage should be considered to consistent of one or several active elements, along with accompanying passive elements)
a) preamp tube --> transistor
This is the typical hybrid design. I built one and I rather enjoyed it. But purists rightly point out there is no power tube distortion, transformer saturation, nor rectifier sag.
OK, let's move on:
b) preamp tube --> power tube (dummy load) --> transistor
This is slightly more clever, but more expensive, and all of the power in the dummy load is wasted. Oh well, we now have power tubes pumping, and at any volume (because a pot can be placed downstream in a buffered transistor stage).
I should note at this point the amplifier is capable of all of the performance traits of the ZOTL, it just lacks the marketing cachet (presuming that purists accept the ZOTL as all-tube).
c) preamp tube --> power tube --> transformer (dummy load) --> transistor
Now we have spend even more money and weight and power than it would take to build your basic tube amp, but we can drive the output any way we require.
However, we can reconsider the output transformer design--given that it doesn't really need to drive an 8 ohm load, we could make the dummy load on the secondary more compatible with smaller and cheaper transformer design. Also, we'd only really need one or two power tubes, yet still have whatever wattage output is required via the power transistors. Does anybody want to own a Fender Champ plugged into a solid state Marshall? I dunno.
d) preamp tube --> transformer --> power tube (dummy load) --> transistor
Now things are getting interesting. Once we decide that our goal is to saturate a transformer, we realize that it's much easier to saturate a small transformer than a large one, and it won't take nearly as much power. Do we need a transformer in that part of the circuit? Of course not, but if it accomplishes our sonic goal, who cares?
Our transformer has now dropped from an $80 unit to maybe $10, and would only weigh a few ounces. The power tube(s) is still screaming away into its dummy load, and we are listening at bedroom levels (sorry, if you want speaker breakup I can't help you)
Let's keep going:
e) preamp tube --> transformer (dummy pot load) --> preamp tube --> pot --> preamp tube --> pot --> power tube --> transistor
Now we can independently set preamp tube and power tube overdrive and transformer saturation (we could even make parallel/series signal paths if we wanted, multiple channels, etc.)
But all of that presumes that in the future people will use guitar amps. You want an invention? Here you go, best of all under current law I don't have to build a prototype to patent it:
f) guitar --> onboard FET/ADC/bluetooth --> iPhone of each member of the audience that receives discrete signals from various members of the band, and according to their preferences applies DSP processes to mix the band as they like. The audience may also participate with their own instruments, or simply wave their iPhone as their instrument. All data is transmitted in a MIDI-type format, such that audience members may select not only the guitar tone they'd like to hear, but even assign completely different patches from what the actual instruments are. Imagine going to a concert and bringing your guitar so you can jam along, but instead of a metal band you decide you'd like to hear them as a gamelan strangely accompanying an Indian classical trio, with you on sitar. If you choose to broadcast your data, other audience members may incorporate your playing at their discretion. No loudspeakers anywhere, just earbuds (and ambient sounds of acoustic instruments). Of course, it doesn't have to be just live, or in just a single location, thanks to the interwebs. And people who can't play an instrument can bring their guitar hero ax to trigger various modifications of the live data coming from the band.
That, my dear Gonzo, is the guitar amplifier of the future!