My experience is that every component needs a break-in period-- cables, amps, speakers, DACs, etc. The length of time may vary from a week or so to several months. Even with just moving interconnects, it may take an hour for them to return to their performance plateau. Many rooms at audio shows are very disappointing on Friday, tolerable on Saturday, and may start sounding up to their capabilities Sunday afternoon just before the equipment is shut down and crated for shipping. Some otherwise excellent rooms are often ruined by one piece of equipment that was hurriedly built and shipped with no break-in.
Regarding the Tortuga preamps, I just received an LDR1B with the upgraded copper wiring. Fresh out of the box, there was a broad upper midrange glare and less than extended bass. After a day or so of a track on a CD set on repeat with lots of intense transients, that glare started to clear up and after three days the unit was coming into it's glory.
One other thing I noticed was that on the first day out of the box, at some impedance settings, I was getting some L/R imbalance and some low level hum/buzz. Again, after a couple of days that all cleared up.
I'd recommend that a new unit be powered on and exercised with transient-rich music for a couple of days before exploring the impedance settings and certainly before making any judgements of the sound quality. Once the Tortuga preamp settles in, it's an amazing product and a huge bang for the buck component.