One question about the DC transformer. I have been doing a lot of reading about power conditioners and it seems like transformers suck out dynamics. No idea if it is true or not as I ended up getting a capacitor based conditioner. If I understand correctly capacitors would be filtering and not isolating. It works well enough for me. It isn't perfect but it is an improvement over the cheapo powerbar I was using.
I have no idea what you mean with DC transformer.
I assume you mean a regenerative UPS.
That one works on batteries (or mains fed) and generates 50/60V AC locally.
The DC on the transformer I mentioned is caused by power lines that aren't 'loaded' symmetrical between the positive and negative cycle.
For instance there may be a higher positive half of the AC linevoltage sinewave than the negative half (or vice versa) for some reason.
In that case there could be a small DC voltage on the AC power line (together with the present AC) and this magnetises the core causing it to audibly hum more in that case than normally.
So as far as I understood from the OP the equipment seems to emit more audible hum at different times during the day.
If such is the case the solution is to either use a regenerative UPS (the GOOD ones are expensive) or try the simple DC blocker circuits.
A different fuse and wiring isn't going to solve anything except fill the holes in the wallet of the electrician installing it.
That's what I am getting at.
The DC blocker circuit is not considered a 'power conditioner' but of course does change the conditions on the power line.
It only removes small DC offsets that could (but normally are never) present on AC power lines.
It can only remove DC voltages up to a few volts but more isn't needed.
Power conditioners exist in many many forms and all of them claim those of others perform badly and reduce whatnot in sound.
The word 'power conditioner' can mean many things ranging from a simple separation transformer to very complex electronic circuitry.
Some claim wonders, others say it changed nothing and all the positions one could take in the middle can be found on the web.
No improvements or (severe) sound degradation to (substantial) increase in perceived SQ can be the result with any of the given devices.
Personally I would only advise on these matters when actually visiting the place and asses what is going on (measurements of AC lines) and used equipment.
If for instance one single device 'pollutes' the AC line (because of filters or used components) and that one isn't isolated and 'contained' it really doesn't matter if you connect the lot on a power conditioned AC converter or the mains as in both cases that component will f' up that AC.
If one suspects AC in the house is giving troubles I would:
switch off as many as possible devices temporarily and switch on audio devices one by one.
Then switch on other devices in the house and try to find what is causing problems (could be a simple LED light somewhere in the house)
In countries with 110 (120V) AC the problems usually are bigger than countries with 220-240V AC as the currents drawn are 50% lower on higher mains voltage power lines.
