Patents in the U.S. run out after I think 17 years, in case the circuit was actually patented. Not sure how the law works in other countries or outside of the country or origin. Updating the transistors is likely to change the phase margin (tendency to ring or oscillate) if there's any negative feedback, so I'd take a close look at how cleanly it goes in and out of clipping with a 10kHZ squarewave signal at least.
The WHOLE Magazine is copyright
And it states so somewhere .
Even if not, it's implicit.
Clear it with Maplin or the Magazine editors first.
EDIT: the University of Cambridge states:
http://www.caret.cam.ac.uk/copyright/Page171.html
that even for "unknown Author", copyright holds for 70 years from date of publishing.
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The WHOLE Magazine is copyright
.
The magazine article referring to this amplifier is also on the internet.
50W HiFi Power Amplifier LW35Q Maplin Kit
copyright doesn't protect circuits - only drawings, manuals, articles, pcb artwork
but the circuit topology, even implemented with the exact same part #s isn't protected by copyright if you lay out your own board, provide your own documentation
in Europe 20 years is the standard for patent protection, the US has changed to match
anything sold, derived from patents and publications older than 20 years are "prior art" - any circuit idea published over 1 year ago is also public domain unless the inventor has applied for a patent - even if the article gets copyright protection - the idea doesn't
but the circuit topology, even implemented with the exact same part #s isn't protected by copyright if you lay out your own board, provide your own documentation
in Europe 20 years is the standard for patent protection, the US has changed to match
anything sold, derived from patents and publications older than 20 years are "prior art" - any circuit idea published over 1 year ago is also public domain unless the inventor has applied for a patent - even if the article gets copyright protection - the idea doesn't
I have used a complete set of different more modern transistors.
I have also laid out my own PCB which is quite different from the original.
Some of the circuit component values have been changed.
I also added a capacitor to the circuit.
The circuit part numbers have completely changed. The pcb was re-annotated so the components numbers flow from the top of the pcb downwards.
The topology is LTP, VAS, Vbe multiplier, driver stage then output stage.
This is quite a common topology.
The only unusual stage is the output stage which is common emitter.
I have also laid out my own PCB which is quite different from the original.
Some of the circuit component values have been changed.
I also added a capacitor to the circuit.
The circuit part numbers have completely changed. The pcb was re-annotated so the components numbers flow from the top of the pcb downwards.
The topology is LTP, VAS, Vbe multiplier, driver stage then output stage.
This is quite a common topology.
The only unusual stage is the output stage which is common emitter.
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I agree with the comments above. I wouldn't call it a Maplin anymore though. Call it a derivative if you want to make reference to the original version. With higher speed parts it becomes more important to have good power supply bypassing right in the circuit area. I'd use 0.1uF caps across 100uF AE caps on each rail to Gnd..
One of the changes was using 470uF across power rails.
I didn't add 0.1uf though. Might do that on next revision.
It is originally a John Lyndsey Hood design.
Sadly John passed away in 2004.
In Europe copyright can cover things which it would not elsewhere (where patents would typically be used instead). A drawing of the circuit is certainly covered by copyright. Derivative works are still covered by the original copyright and the copyright of the modifier, so a modified circuit has two copyright holders. The real issues are:
- does your circuit look like a (perhaps partial, somewhat modified) copy of the original?
- did you actually copy the original or start afresh?
Note that in Europe copyright does not have to explicitly claimed in order to exist; copyright comes into existence automatically as the work is created. The only requirement is that it is indeed a 'work': something which involved some creative effort (but not necessarily very much!) and is not the way it is simply because it could not be any different.
Contacting the original copyright holder, as you have done, is the best way forward.
- does your circuit look like a (perhaps partial, somewhat modified) copy of the original?
- did you actually copy the original or start afresh?
Note that in Europe copyright does not have to explicitly claimed in order to exist; copyright comes into existence automatically as the work is created. The only requirement is that it is indeed a 'work': something which involved some creative effort (but not necessarily very much!) and is not the way it is simply because it could not be any different.
Contacting the original copyright holder, as you have done, is the best way forward.
50W HiFi Power Amplifier LW35Q Maplin Kit
I think I know all JLH's transistors power amp designs,
and this one does not belong to them.
Compensation using C3 is avoided since long and was certainly never used by JLH who has always shown a preference for schemes connecting a cap form the VAS to the inverting input.
I think I know all JLH's transistors power amp designs,
and this one does not belong to them.
Compensation using C3 is avoided since long and was certainly never used by JLH who has always shown a preference for schemes connecting a cap form the VAS to the inverting input.
Part of this depends somewhat on what you will actually DO with your version. Are you going to sell it as a kit? Sell it as a finished board (semi-kit)? Or sell it as a finished amplifier? Or perhaps use it in a bundled package?
Also the way that you market it in *practice* has an impact.
Nobody is likely to care one way or another about a little "mom & pop" operation cranking out very limited and small quantities of product - legal or not. Otoh if you turn out even a little product with the brand name of a big name, or the exact look of a big name, expect problems.
But, it might be best to look for another design (there are so many) to market, since ur treading on something that is being marketed in your country and area... could stir up some trouble (again depending on what ur doing).
Oh, it does make a difference if ur doing this as a hobbyist or under the aegis of a legit business. As hobbyist, doubt anyone would do more than write you a letter, if they cared about this at all.
Also the way that you market it in *practice* has an impact.
Nobody is likely to care one way or another about a little "mom & pop" operation cranking out very limited and small quantities of product - legal or not. Otoh if you turn out even a little product with the brand name of a big name, or the exact look of a big name, expect problems.
But, it might be best to look for another design (there are so many) to market, since ur treading on something that is being marketed in your country and area... could stir up some trouble (again depending on what ur doing).
Oh, it does make a difference if ur doing this as a hobbyist or under the aegis of a legit business. As hobbyist, doubt anyone would do more than write you a letter, if they cared about this at all.
Even as a legal business, unless they have a patent on some feature of the circuit, they have no legal grounds to prevent him from producing the amplifier.
That said, there is nothing to stop them from filing a (harassment) lawsuit against him to dirve him out of business. They don't have to win a case to accomplish it.
That said, there is nothing to stop them from filing a (harassment) lawsuit against him to dirve him out of business. They don't have to win a case to accomplish it.
Considering France, the UK, Germany, and many others are parties to all the international patent treaties, I would find this hard to believe.
Let me rephrase: in Europe it is traditional to use copyright to provide protection which elsewhere might use patents. The classic case is software. The law (in practice) is not just what statutes and treaties say, but also how courts have usually chosen to interpret it. However, there is a drift towards using patents instead.
In order to use a circuit you almost have to 'write it down' - which includes storing it in a computer. If it is a copy of another circuit then you have infringed the copyright on the original. Nobody would know until you start selling your equipment. At that point other people need to know the circuit, or some enterprising hobbyist might draw out the circuit. In any case, if you construct and sell a PCB (of your own design) you would have a hard job convincing a judge that you never actually wrote out the circuit itself - the idea went straight from your head into an original PCB design without any copying taking place?
In order to use a circuit you almost have to 'write it down' - which includes storing it in a computer. If it is a copy of another circuit then you have infringed the copyright on the original. Nobody would know until you start selling your equipment. At that point other people need to know the circuit, or some enterprising hobbyist might draw out the circuit. In any case, if you construct and sell a PCB (of your own design) you would have a hard job convincing a judge that you never actually wrote out the circuit itself - the idea went straight from your head into an original PCB design without any copying taking place?
This is definitely not the case with any European company that I have ever dealt with. You would have to site some case law.
Example here on reverse engineering would also contradict that statement. This is written by lawyers, and cites cases.
http://people.ischool.berkeley.edu/~pam/papers/l&e reveng3.pdf
It is important to differentiate between software and hardware. Virtually all the action on this topic these days seems to be on the software, that has nothing to do with the subject, a circuit. For $20,000 and 5 LEGALLY obtained samples (this is very important) you can buy a reverse engineered schematic of an IC from any of several vendors. If no patented IP is found it is perfectly legal to copy and sell anything you find. This has been going on for decades here, in Asia, and in Europe.
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