When you change the input levels using the four knobs, are the changing level values displayed numerically, or does it change the levels without telling you what the actual levels are?
I'm trying to figure out whether you can match its four channels very closely, beyond what you could do by eyeballing the meters.
On the DR-680, when you change the levels, it displays the values in 1 dB steps. It also allows ganging channels together, which I don't expect the DR-70D does.
This was discussed in Part 3 if the thread I believe, and a lot of this is also in the FAQ:
The levels of each channel are only displayed graphically. The highest peak value of all 4 channels is shown numerically in the lower right. There is no per-channel numeric readout; you have to eyeball it. There is no ability to gang channels together either.
All of these are things many of us here consider issues that can easily be fixed by a firmware update, which is why they are in the Update Requests section of the FAQ. Personally, I consider the metering / display the #1 issue that needs to be addressed.
Gain changes in 2dB steps, and is displayed as such on screen (but remember your only seeing the current highest peak value of all active channels). I found through testing that when moving a gain pot, the level is changing in 0.5dB increments. Tom, our Tascam rep here confirmed that the gain actually settles into 2dB steps once you stop moving the pot.