I own the EAR 864, 912 (and a phono pre 324). For both preamps, phono is the primary value to them. The line stages with rolled tubes and fuses, high end power cabling sounds much better than stock. HOWEVER, both have 1990s Tim designs lacking true power regulation although he thought his cheapo method would work (it did in the 1990s). Then nasty power for most people occurred with computer and phone line, internet use dirtied up power coming into people’s homes. For those who live in hot regions where A/C is essential (like the Southwest in the middle of summer), the power is either corrupted and/or inadequate to supply proper clean voltage regulated power. These two preamps suffer during peak use hours and sound bad. Then by nightfall after 10pm or 12 am, the preamps bloom again and sound great for phono and okay for line stage.
To alleviate and elevate the sound, my friends and I use a Tripplite voltage regulator for the EAR preamps. That helps both day and night. However, I then unplugged it when using another preamp as something in the big transformer muddied the sound.
I have since switched to a more expensive premap with SOTA DAC, the Lampizator Poseidon. It has a very superior soundstage and regulated power supply. It also elevates the sound of the 912 phono with RCA outs to the Poseidon. I will be experimenting with a solid state EAR 324 phono preamp to see whether it requires an SUT (Zesto Alessis) or not and if it does or doesn’t have a power regulation problem like the tubed preamps.