JohnRoberts said:
I first wrote about this in 1980 but it hasn't changed much, at least for analog console/mixers. The heavy lifting for S/N and fidelity is first the mic preamps, and secondly the sum bus.
I know JR is very vocal about this and we had this discussion before. I guess John is not a studio SE; his POV is that of a designer. I know he can prove his point easily, just as I could, with just a few measurements or a plain and simple level diagram. But the AP's "needle" doesn't say all.
I am both a designer, SE and musician. I know how to play the hat game. When I sit in front of a mixer, I don't think as a designer or a muso. And in this situation, the first thing that gets my attention is noise coming from the monitors with all faders down. Mix bus noise is abnormal (I know it is scientifically normal, but I mean unconsciously, I expect no noise when no fader is up, that's how stupid SE's are).
When I raise a fader, I expect, as anybody, technically trained or not, some noise to come up, so the "track noise" is something I will care later.
Although the hierarchy of priority is technically right, the mix bus requires more attention than the mic pre. It is relatively easy to approach theoretical limits of a mic pre by a dB or two; it will take a lot of work for improving - the law of diminishing return.
OTOH, mix bus are generally so far from the theoretical limits that they offers a lot of space for improvement. Between the standard VE mixer where noise grows linearly with the number of injection resistors and the theoretical "no-noise added" true-current mixing, through "multiple-partial" mixing, there are are several techniques that provide sensible improvement of summing noise. The fact that it is not very influential on the final mix does not justify deeming it as secondary. The comfort of the SE is also a significant parameter.
In that respect, I'm very happy with the absence of audible bus noise on my digital mixer.
Abbey, please don't forget TS24/48.
I don't.
The thing is, I finally got hold of the TS24 schemo, just to find that the mic circuit in there is the same as the 6000. My memory playing tricks with me. After talking with an ex-colleague, we came to the conclusion that the mixer I was thinking about was not the TS24/48, but the 3200. The schematic diagrams are about 1m x 2m, so I have to go to the ex-company and try to make copies, perhaps manual copies... The summing amps in the TS24 use a common-base bipolar PNP running at about 1mA, followed by half a TL0.