Right. I read the article and found an article describing techniques that are commonly used to hot rod an amplifier. It seems well written and may describe a unique combination of hot rodding technique as they were applied to ONE particular amplifier.
Just as in hot rodding an engine (your analogy) the common methods apply to most, but not all designs, and not all techniques will yield the same gains in power with minimal reduction in reliability in every situation. You can't patent boring out an engine block as it is a well known method to increase power. It also reduces reliability and does not work in all cases. You can't patent the combination of boring, stroking, and installing bigger valves since they are all well known methods.
I also see a TM mark next to the Supermods name. Is it actually a registered trademark? The US PTO search engine returns nothing. Google returns only hits related to video game hacking.
Operating the output transformer at half impedance is a technique that has been discussed on this forum since before I joined. 1/4 and double impedance has been discussed too. So have multiple OPT's per channel. As I stated before this works great on some OPT's and doesn't work at all on others. OPT's that have a lot of DC resistance are usually not good choices. The One Electron UBT series are examples of a transformer that doesn't work "ratioed down".
Adding auxillary power transformers to boost the heater current and / or the B+ voltage have been discussed here forever as well. I just answered a forum post where a member was discussing the correct method for squeezing more power out of his guitar amp. Switching to solid state rectifiers is a valid choice and a standard option on my SSE amp which has been available for 5 years. Many people believe the use of solid state rectifiers degrade the sound quality, and prefer to add an auxiliary transformer.
Adding a second set of output tubes? Why stop at a second set. People here have gone as far as 7 sets of output tubes in parallel. I mentioned my double SSP because it was the first example that came to mind.
Extrordinary feedback??? Many builders prefer to reduce feedback. It is also prudent to connect a dummy load and a square wave generator and tune the feedback level and compensation to the amplifiers new operating point. I don't find this "extrordinary", just good engineering practice.
OK, whatever....I have been hot rodding tube amps for well over 40 years. Most people who follow my antics here know this. A recent example...
Pete Millett designed a mild mannered stereo amp that put out a conservative 18 WPC. I stated up front when I bought his board that I wouldn't be happy with anything less than 50 WPC. The most I have squeezed through a single board was 525 watts using 4 output tubes, a half impedance transformer, not one but two auxillary power transformers, but alas, no extrordinary feedback, I just tweaked the Schade feedback level, and eliminated the GNFB to get the best sound. I then dialed things back to a more reliable 125 WPC and posted the design for many builders to copy.
http://www.diyaudio.com/forums/tube...p-p-power-amp-design.html?highlight=red+board
I didn't suggest that you intended to patent this "invention", it just seemed odd that you would use the term "prior art" in this rather casual discussion on a forum.
The patent ship has sailed already. Either you already applied for a patent or you can't. Once you publish it it's public domain and you can't patent it later.
Anyway, as to the technical question of "is it obvious to one skilled in the art", I will quote a patent examiner who once said to me: if you can go out and hire "one skilled in the art" (in this case a competent EE) to achieve the stated result, then it is "obvious".
The patent ship has sailed already. Either you already applied for a patent or you can't. Once you publish it it's public domain and you can't patent it later.
Anyway, as to the technical question of "is it obvious to one skilled in the art", I will quote a patent examiner who once said to me: if you can go out and hire "one skilled in the art" (in this case a competent EE) to achieve the stated result, then it is "obvious".
True in Europe, not so in the US- here, you have a year following public disclosure to file an application. That said, there's nothing even vaguely defensible here for patent purposes. You might be able to buffalo an examiner into allowing some claims if you caught the right one on the right day and he was sloppy in examination, but no way the patent could withstand a challenge.
I wasn't aware of that distinction. While I don't claim PowerDrive to be a unique idea, just a stupid name that popped into my head one day, I consider Tubelab to be my trademark even thoough I haven't had the funds to register it. I will apply the TM to my web page with the next update.
I have also been made aware of a trademark on a name I previously used involving the word "Simple" and the common abbreviation for Single Ended. I can no longer use those words together since searching for their product name on Google brings up a page full of hits for my amp. Their product is a home theater box, so it is in a similar market.
I hold 7 patents in the field of RF communications. I am fully aware of how broken our system is and what we currently have for examiners in Washington. I and the legal team spent several hours attempting to explain the difference between the words intermodulation and demodulation to an examiner who had no clue, and no knowledge of the field. He initially found a ton of prior art discussing demodulation, when my invention was teaching ways to reduce intermodulation distortion in radio receiver front ends. This had reached final action and ALL of his prior art had no relation at all to the invention. When we requested a senior examminer to review his action, he flipped and allowed all claims.
Having a patent just allows you to sue suspected infringers in court. Although not so applicable in the tube world, there are many examples of infringement occuring today at the IC level. Proving or even discovering infringement when it is buried 7 layers deep in silicon inside a custom IC is nearly impossible. For this reason you are seeing fewer applications for patents related to advanced IC circuitry.
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I don't see anything novel about lowering the impedance of a transformer to alter the power rating, this has been well known for decades. Just look in the MIT "Magnetic Circuits and Transformers" book, 1943 or RDH4 1934...1953. (or any number of transformer design books like Grossner, or Lowden, or Reuben Lee, or Nordenberg or the lamination manufacturers design notes or articles by Crowhurst.) Winding resistance will set a practical limit, so only OTs built when copper versus steel was cheap will likely work. The same leakage inductance but lowered Z's will reduce the top end frequency also (making additional stable feedback more difficult too). Not commonly known by radio repair shops is not the same thing as not known by designers and academics.
Parallel tubes, get serious, come on.... It's also obvious to use bigger tubes.
Extra filaments transformers, " "
More feedback, " "
Only possibly unique element would be the simultaneous combination of all these in one unit, and then one has to ask if this is really still HiFi and non-obvious.
Parallel tubes, get serious, come on.... It's also obvious to use bigger tubes.
Extra filaments transformers, " "
More feedback, " "
Only possibly unique element would be the simultaneous combination of all these in one unit, and then one has to ask if this is really still HiFi and non-obvious.
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To Tubelab:
You have fallen into the trap of thinking that, for something to be a patentable invention, there must be at least one element which is wholly new. Not so. A combination of elements, each of which is well known, can easily be an invention. So most of your comments are irrelevant. It doesn't matter how many projects you have done that didn't include all four of the elements of this invention.
To Sy:
You have fallen into the trap of thinking that, for something to be a patentable invention, there must be at least one element which is wholly new. Not so. A combination of elements, each of which is well known, can easily be an invention. So most of your comments are irrelevant. It doesn't matter how many projects you have done that didn't include all four of the elements of this invention.
To Sy:
And what is your experience in patent law? I presented mine above. I also explained in detail why this invention would not be ruled obvious. The only other challenge is to find prior art. As I said to a previous poster, I challenge you to cite published prior art, which embodies all four of the elements of this invention. I don't think you are going to find it.
I doubt your claim to all four elements inclusive is going to hold water. I'm fighting with an "Examiner" at the moment over a patent I hold. All this Examiner cares about is prior art to each individual piece of my patent. He/She does not care whether they are combined in a prior art or not. However, like George's case this Examiner does not understand electronic theory and is missapplying several prior patents so I still have a chance of defending it. Our patent attorney are glad to have the work ;^}
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Two of the four elements cited here are conflicting. Lowering the OT's Z causes the fixed leakage inductance reactance to drop the high end frequency response. Lowered frequency response makes application of additional neg. feedback more problematic. No competent designer would have considered this combination. Hence no prior history of all four elements combined.
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And I just explained to you why it would. I can go out any day of the week and hire a competent EE who hasn't read your article and he/she would easily design a modification that includes all 4 elements and more.
Once I state the design goal of increasing the power without replacing the OPT, everything you described, and more, is routine design work and not an "invention".
There is a big difference between something that hasn't been done before and something that hasn't been done before because nobody was smart enough to do it.
I think SY has us both beat in the patent department.
I probably could but don't have the time to search, nor do I care to. I can find several examples of new granted patents on tube circuits that are obvious to those skilled in the art, blatant copies of prior art, and previously published....often in a college textbook long out of print before most of todays examiners were born. Typically each novel element is a seperate claim which must stand on its own merits, but as I said our system today is broken and just about anything goes if you have enough legal horsepower.
I wrote an article detailing a novel method for improving the efficiency of a tube amplifier using a combination of DSP control over bias and power supply modulation. It was published in Circuit Cellar magazine a few years ago. About 6 months after it was published I received an email from a major US tube amp manufacturer showing me a patent application filed in the UK where some of the claims were copied from my article.
To TheGimp: I know nothing of your patent case, so I can't comment on that. All I can say is that, for prior art to conflict with a patent claim, it must embody all elements of the claim.
To smoking-amp: This amp works fine at the high end. You can't argue with success.
To dgta:
To smoking-amp: This amp works fine at the high end. You can't argue with success.
To dgta:
--- That is nonsense. Perhaps you meant could instead of would. That takes it out of the realm of obviousness. The rest isn't relevant to patent law. I have quoted the test for obviousness before, in this thread. Apparently, you didn't understand it. Generally, for a claim to be ruled obvious, the prior art must point to the very combination of elements in the claim. Not only does the conventional wisdom NOT point to this particular combination, two of the elements are actually deprecated!
It is not only dead obvious that it would work but we can find many cases of ampliers being designed like this from the beginning. Everyone knows that you can hook up the speaker to a lower impedance tap and lower the impedance is reflected to the values. (Check out some old guitar amps that use 4 ohm speakers) also it is pretty common to "modify" amps by replacing the tube rectifier with sold state. In fact you can buy an octal tube base with diodes inside just for this purpose.
I think I've even seen a commercial built amp (I think a 120W Ampeg) that had a switch to convert between 2 and 4 output tubes and then the OPT would run at half impedance. They sold thousands of these "convertible" amps. The trouble was that you had to switch both, it was not a combined switch. More than a few users messed up.
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To ChrisA: The fact that it seems obvious to you (after the invention is published) that it would work means nothing. The question is whether the prior art would lead you to this specific combination of elements. I remind you that one of the elements, is the use of extraordinary negative feedback to allow hifi operation, deep into the saturation region of the output transformers. Again, trotting out examples of cases which did not use all of the elements of the invention does not prove prior art or obviousness.
By the way, the technique is only directed at hifi amplifiers. Band amps are a different animal entirely.
By the way, the technique is only directed at hifi amplifiers. Band amps are a different animal entirely.
The combination of techniques here will only work for an OT that has extra heavy copper wire internally and excessive bandwidth for the original application. How many amplifiers are built this way? You would be waisting your money pursuing a patent of such meager financial value, regardless of any technical patentability issues. And then a patent is only useful if it is defendable. Shaky technical merits would make for an expensive defense and would not deter anyone who felt it had no "clothes" anyway.
Well, I have to amend my last statement, since it appears that many of the patents issued in the audio realm are for marketing purposes only. But you have to have something worthwhile to market to bear the patent expenses. For a scheme like this, you would be better off using parts optimised for the intended use in the first place.
Well, I have to amend my last statement, since it appears that many of the patents issued in the audio realm are for marketing purposes only. But you have to have something worthwhile to market to bear the patent expenses. For a scheme like this, you would be better off using parts optimised for the intended use in the first place.
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You've been shown several good starting points. My fees for searches and patent analysis are available if you drop me a PM.
To smoking amp:
You are quite right, that pursuing a patent would be of meager financial value. No one is doing that, at the moment. It came up because someone raised the question whether or not this is a new invention. I contend that it qualifies, under US patent law.
--- I don't see how you can justify that statement. In any case, the Eico ST-70 was a kit designed for low cost. While the output transformers are pretty decent, they have been referred-to by experts as "everyday." Certainly nothing extraordinary.
You are quite right, that pursuing a patent would be of meager financial value. No one is doing that, at the moment. It came up because someone raised the question whether or not this is a new invention. I contend that it qualifies, under US patent law.
I don't see how "band" amplifiers differ from hifi amplifiers in this regard. Push-pull 50 Watt Marshalls have two EL34 tubes and 100 Watt Marshalls have four. The parallel PP transformer will have half the primary impedance. The only difference I see is that Marshall would use a higher rated transformer for the higher power output.
Guitarists regularly pull two tubes from a 100 Watt amp to drop it to 50 Watts for small venues, changing the speaker impedance selector to maintain the impedance ratio.
I don't see any invention or innovation here. But if I ever feel the need to melt an OPT I may give this a try.
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