Not exactly.
A circuit has to be patented to be protected, and to be patented it has to be both significantly original and a significant device.
So, virtually no analog stomp is patentable because they're all very clearly derivative of each other and are doing mostly the same things.
It's all just tweaking at this point. Nobody owns the dirtbox. Get over it. There
is no ethical or legal question here. See my linked posts.
Instead, having lost the patent issue, attorneys for various bloodsuckers who want protection to which they are not entitled try to twist obscure trade dress and copyright issues
in lieu of patent. A notorious example being the Re-an interlocking plastic corner. Or the ridiculous cases against Behringer.
A few do. Digital stuff has some
copyrighted embedded programming, I believe, as well.
That's OK, I'm categorically saying it
IS right, and the originators of American patent law and a couple of hundred years of case law are 100% on my side.
To understand this issue once and for all, you need to read the excellent chapters on the intention and history of patent law contained in (of all places) this book:
Your library should have it.