I bought a pair of E5s - they sound good, but there's a low-level hum coming out of the larger speaker on each unit - and a mechanical buzz from the case. Looking online at various reviews, I see this is an incredibly common complaint. I just wish I'd read these first, but I like PreSonus gear, and didn't expect this.

I've since heard several other E5s, and they have exactly the same problem so it's a design thing not so bad if you're playing things loud, but horrible if you're listening to quiet stuff.

I'm not planning to return them again as they're now in use.

My question really is - is there a circuit diagram for the power amp circuit board as I'd like to replace the power supply with something better (which falls under my own electronic expertise, having design mains-powered systems in the past).

I'll do it without the diagram, but it'd be better all round to do it WITH.

Thanks