Okay, I'm feeling dumb today. I've been trying to wrap my head around the fine tuning procedures for a couple days (just in terms of which components to place, I haven't actually started the fine tuning process yet) and I want to make sure I am clear on this.
I have the revision v2.5 boards.
FT1 - all that is needed here is the 10k trimmer, right? By my math, it looks like I should pre-trim it for approximately 4k ohms and adjust on test. No fixed resistors for R7/8 in this case.
FT2A - You either place a 12k resistor in R22 and jump the middle and square pads of FT2A, OR you install a 10k resistor for R22 and a 20k trimmer for FT2A for adjustment.
FT2B - A 2k trimmer (FT2B) is installed instead of R56.
My question on FT2A is, if the rough target resistance for R22 (or the total resistance between T5 and R25, as it were) is 12k, why does the second option use a 10k resistor and a 20k trimmer in series? Wouldn't a 5k trimmer make more sense? Or am I missing something here, because I'm feeling like I'm missing something... I see that you mention in the guide that your right channel's final value for R22 was around 18k, so I guess the larger trimmer value is to compensate for wide swings like that?
And one final unrelated question: For C13, what are the pros/cons of using a tantalum instead of a regular electrolytic? I have used tants in other builds when called for, but I always hear such conflicting information about whether they are good or bad. Given the option here, I don't know what to choose or why.