I will say, based on the posts, there seem to be a lot of people who want the main channel knobs to control gain (pre-fade gain). As noted, this can be done using Basic mode or by using Custom mode with gain set to basic.
Just to clarify - My understanding is that there is not currently a way to get the channel knobs to control pre-fader gain.
In Advanced mode, the MP6 has two user-adjustable gain stages. The first stage is a trim pot (called gain on the MixPres). This is an
analog gain stage and controls the analog level of the microphone preamp itself. It is adjusted by turning the headphone controller in the channel menu. The second stage is the fader, which is a
digital gain stage. It is adjusted by turning the channel fader knob.
This sets up what is traditionally SOP (standard operating procedure) on many film and television shoots (which is of course a large part of Sound Devices' background). There, you often want to set your analog trim to a good but conservative level and focus on the mix using the faders. That way a mixer has total control of the mix, but the ISO's also serve as a safety in case something gets suddenly loud and clips. The sound mixer's fader mix is usually used for picture editing, screenings, and the like, and the program is eventually re-mixed in post production using the ISO's. In post it is no problem to have the ISO's to be a little low in level, as they can be turned up digitally without adding any noise - digital gain will not add noise when done properly. So in Advanced mode, you have your ISO's pre-fader and controlled
only by the analog trim, and your mix track post fader and controlled by both the analog trim and the digital gain of the fader.
When you change Gain to Basic (usually in Custom mode), two things happen. First, that analog trim is disabled from being user-adjustable. It is fixed at +6db (the lowest setting) and is greyed out and cannot be changed in the current firmware. Second, basic gain mode switches the ISO channels from pre-fader to post-fader. That way both the ISO's and the mix (if active) are controlled by only the digital fader gain stage. This is a bit different from having the channel faders control the pre-fader analog gain.
In theory it is no problem to not have access to analog gain with a device as good as the MixPre's are. As I mentioned before, digital gain should add no noise to a signal, so if you have a preamp which is quiet enough that the self-noise of the preamp does not overpower even the quietest signal then you have little to lose by simply recording with the preamp gain down and raising the volume digitally in post. This has the advantage as well of preventing even surprisingly loud signals from overloading the A/D converters and causing clipping. Sound Devices' new Kashmir preamps seems purpose-built for this kind of recording; they are certainly quiet enough and have a wide enough bandwidth to be able to do this. This seems to be what Sound Devices is recommending in a lot of their marketing literature as well.
In practical use though, there are a couple of disadvantages to this way of working, mostly in terms of monitoring. First of all, if you monitor anything pre-fader while in Gain-Basic mode, it will be very hard to hear. Remember that pre-fader monitoring only responds to that first, analog trim stage which in this mode is fixed at +6 db. So if your sources need more gain than this they will seem soft in your monitoring. This makes recording low level sources, like nature ambience for example, quite difficult in gain-basic mode. For some sources, the digital gain available on the MixPre alone isn't really enough to get the sound to a clearly audible level. Again this isn't really an issue with recording quality as the file can always be given more digital gain after it is recorded, but that is an extra step and makes monitoring in the field quite difficult. In these situations you end up cranking up the headphone amp on the MixPre as high as it will go just to hear the signal. This is also not ideal though because the headphone amp is an analog gain stage and will induce noise on what you're hearing. Although this noise won't affect the recording, it could definitely trick you into thinking your recording is noisier than it actually is.
That's why the request to have an option for the channel fader knobs to control the analog preamp trim is still a popular request. There are great threads about the MixPre both on the JWSound Group and on Gearslutz with a lot of great info. I post as "mobilemike" on jwsoundgroup.net and as "celticrogues" on Gearslutz.
Hope this helps a bit.
-Mike
