A super gainclone…
March 8, 2021 2 Comments
Does the world need another Gainclone-type amplifier? Probably not, and I certainly don’t either. However, here’s one I managed to overlook until very recently, and it is called – rather immodestly – the “Super Gainclone” 🙂
It’s designed by Bob Cordell (who does know a thing or two about amplifiers it has to be said) and it comes from one of his books. It was “launched” on diyaudio with this thread and I’ve somehow managed to completely miss both the design and the associated PCB group buys until a few months ago when someone was offloading a few excess boards which I purchased.
The circuit is based on the LM3886 IC (more or less the only one of these ICs still in production) and it isn’t really a “barebones” circuit as is often the case with GCs. Instead, it incorporates an input buffer, a DC-servo and an optional soft-clipper circuit (called “klever klipper”). Cordell has also retained the general “best practice” decoupling and stability parts (e.g. the output LC) that often get left out by overzealeous DIY’ers who thinks that these are not needed or even compromising the sound quality. However, unlike many other of the more “complicated” GC designs this isn’t a “composite” amplifier (where the input opamp provides a lot of the gain), so maybe there is room in the world for one more GC variant after all?
The board layout was done by Mark Johnson on diyaudio and it is very good, but also look nothing like I would have done them and some of the footprints are definitely not ones I would have used – that’s a minor thing though. Along with the amplifier PCB layout, Mark developed a matching PSU as well. It’s a pretty simple design but it should work just fine for this application. I do hate the upright (“tombstoned”) resistors, but it’s not exactly the end of the world, is it?
The reason for the blank capacitor positions is that I have no case design for this one yet so I don’t want to make a choice on caps already now. Similarly, trimming the clipping circuit takes a bit of time and as mentioned I don’t really have a case idea yet, so I’ll save that for later. However, after a string of builds that either didn’t behave as expected or plainly didn’t work, just getting something together that actually powered up as it should feels as a “win” right now 🙂