I have a set of older SE846 IEMs, I can give them a try tonight to see how they do on the lowest gain setting on both balanced and SE, and see whether the noise floor is audible.
So, the stack I tested with:
- DX7s DAC, in DAC mode (max gain), balanced connections into...
- JBL M-Patch 2 passive switch (max gain), balanced connections into...
- THX AAA 789 amp (lowest gain switch setting), feeding into...
- Shure SE846 IEMs circa 2014, using a balanced cable and adapters for both 4-pin XLR and 3.5mm TRS
3.5mm SE: I have to stretch to hear the noise floor at max volume; if I know it's there, I can listen for it (specifically, if I lower the volume and raise it to max quickly), but you'd be hard-pressed to notice it in regular use. I found reasonable listening levels to be about 1/4 to 1/2 of the amp's gain range depending on the source material, so I didn't find it necessary to lower gain at the source at all.
4-pin XLR: it's quiet, but you don't have to focus to notice the noise floor in the top 10% of the volume range. That said, if you try listening to actual source material at max volume, well, you won't have the problem of hearing the noise floor for very long.
At reasonable listening volumes, I quickly stopped noticing it, but someone more sensitive (or listening at higher volumes) might be irritated. I found that I had too little gain control directly on the amp, and wound up lowering the gain on the M-Patch 2 to give the amp more range.
On anything but the lowest gain setting, the noise floor is clearly present on both SE and balanced.
tl;dr:
- Only low-gain, and SE is best
- Reduce output gain at the source to give you more control on the amp
- On XLR (with source gain reduction) you'll probably hear the noise floor in quiet sections