It is ALL about the EAR, NOT the GEAR!
This can be done legally because very few circuits are actually patented, and only brand names / designs can be copyrighted.
Here some thoughts and some collection of texts found on the web.
1. Cloning a particular amp is one thing, where you just build the amp using the original schematic/specs, matching the values of all the components to the original design values. Blueprinting a given example of an amp, measuring the actual value of each resistor and cap is another matter. Blueprinting takes into account the aging process to a fair degree, but there is still the issue of trying to wind the transformers to match the aged original transformers. Then of course the blueprint clone begins to age.....
2. As long as a clone was built well they should function the same. If you get someone building a clone in their living room that might get sketch, but there are plenty of good companies cranking them out now.
3. Wether or not Behringer clones are better or worse than the originals will always be up for debate. Sound is subjective and buyers preferences are individual making one product not necessarily better than another. However, affordability is typically king when it comes to any sort of music gear purchase and Behringer currently has that in the bag. The TR-808 will cost you up to $6,000 but you can pick up the RD-8 for $398 on stores. An original Minimoog will set you back $7,000, but a Behringer Model D clone costs $298 on stores.
These are certainly interesting & murky waters! Personally I have much more of an issue with the idea of Behringer selling numerous ‘clones’ which rely heavily on the name & history of the original components / instruments. Remaking old chips that were designed, and sold commercially, 40 years ago is less of a concern in my mind.
I’d encourage folks to separate out the issues here – you can dislike Behringer for numerous reasons, but I’m trying to stop my personal distaste of their business model from automatically decrying everything they do as destructive to ‘the community’.
Think for a second why it’s more ok for Moog to ‘remake’ the Minimoog, than for Behringer to make a ‘clone’? I’m not a big fan of thinking the Moog Corporation has an indefinite moral right to profit from a now unprotected design. When it comes to the Curtis chips, remember that they were designed from the beginning to be sold commercially and put in synthesizers, which they were in large numbers, and with the knowledge that those designs wouldn’t be protected indefinitely. I’d be surprised if Behringer didn’t try to buy out Curtis rather than doing it the hard way with the supposed 6 figure IC setup costs.
None of this is to say I appreciate what Behringer is doing. They are openly pursuing hyper-capitalist goals, and their business plan is one that makes it impossible for small manufacturers to directly compete commercially. I’m not bitter about that, it’s just a reality. The consequence though is that it allows Behringer to make a lot of money doing boring things – which actually leaves more room for innovation amongst the small manufacturers. Behringer products are cheap, in large part because they focus on a very different kind of R&D (manufacturability & scalability focused). The only problem is when customers complain that the BOM->Retail markup is too much for innovative products, rather than accepting that they are two independent value propositions.
In terms of the Mannequins eurorack modules, the first 3 modules I designed were largely enabled by the Cool Audio recreations of the ssm2164. I’m super grateful that these out of production components were made available, and in new surface-mount packages – I literally wouldn’t have been able to design what I did without them. I am appreciative that the components weren’t made only for in-house use – at a guess there’s probably hundreds of euro modules that wouldn’t exist without them, and they also enabled the Elektron Analog series. That said I’m choosing not to design with those parts into the future for numerous reasons.