So, one thing that would make it sound more open sounding is to remove the steel plate over the transformer and removed the steel bolt.
I’ll let you in on a secret. Use Non-magnetic stainless bolts and then you don’t have to go thru all that. A regular steel bolt heats up because its a magnetic resistance to the transformer and typically runs hotter than the transformer itself! Change it out to stainless and the transformer draws less power and runs cooler- and may well put out a slightly higher voltage. But FWIW due to the high amount of feedback, the class D has a lot of power supply noise (and voltage sag) rejection. Class D amps running less feedback will benefit more on this account.
The Cardas binding posts are good but even better is to get rid of the posts, put slightly longer wire on the output and clamp that wire directly to your speaker cables using nylon bolts, washers and nuts sitting right outside the binding post holes
Anyone doing this is really asking for trouble! To start with any manufacturer would void the warranty in a heartbeat. It also doesn’t go down well unless you live in a mancave wearing cargo shorts and no hope of a date :) ... if you get my drift
Of course, you would want to put a Furutech super IEC inlet on the amp and get rid of the stock inlet. Get a fuse holder from Acme and wire it off the Furutech inlet and get one of those new yeller fuses from Quantum Science......
This is a really Bad Idea. In our case there’s an AC filter on the backside of the IEC connector (the amp in the video is from the first production prototype run). If this isn’t present, there could be noise issues. In our amp, the rectifiers in the power supply are the main source of noise and we did a lot to snub them, but the noise filter was added to really make it silent. In this way it puts out less noise on the AC line than most tube amps. You could change out the fuse but I think you’ll find that due to the large amount of feedback, the minuscule voltage drop across the fuse will have no effect whatsoever.
How about changing the op amp on the input to a discrete one? Discrete op amps are generally more real and open sounding.
Here’s another thing I’ll let you in on. What is important in opamps is something called Gain Bandwidth Product. If you have enough to support the feedback in the circuit, there will be no ’sound’ of the opamps other than noise (and in our case the noise floor of the amp is mostly from the opamps). Back in the 1960s and well into the 1980s opamps did have a ’sound’ which is why if you have to change out an opamp in a vintage guitar effects pedal, its important to find an exact replacement or the pedal won’t sound right (guitar players are quite picky about that sort of thing!). Our input buffer has a gain of 2, which is to say there’s a lot of feedback and with modern opamps, as long as you don’t ask more than about 20dB or so, they will be as neutral as you can get.
A friend of mine designed one of the higher performance discreet opamps out there (back when it was still worth it) and he’ll be one of the first to tell you what I did above. IOW doing something like this will result in no benefit whatsoever. To design a class D amp you can’t just wing it by plopping parts in; you have to do the math and understand the engineering behind it.