Newbie question - uses for summing busses (e.g. Neumann 475)

I have been looking at a Neumann 475 summing buss/mix buss amplifier with OA10s
(says I who knows nothing about that last line)
here is a schematic
http://www.gyraf.dk/schematics/Neu_v475.gif

Three questions...
What are OA10s?
What is a summing bus/mix bus amplifier used for?
If it is the same thing as one of those Neve 1272s - can I use this module as a mic preamp and how easy is it to modify?

The summing buss amplifier is the actual mixer. The OA10 is a discrete opamp manufactured by Neumann.

[quote author="[silent:arts]"]
(..)
Neumann OA10 schematic:
http://www.silentarts.de/lab/studiotechnik/neumann/OA10_Schematic.pdf
Neumann OA10 data:
http://www.silentarts.de/lab/studiotechnik/neumann/OA10_Data.pdf
(..)
[/quote]

Thanks you very much for the replies....

I have looked at the data sheet and the schematic of the 475
One thing puzzles me....

In the Data sheet (Figure 10) and by definition the summing buss takes multiple inputs and produces one output

However is you look at the schematic of the 475 - there are two inputs - each going into one OA10 (which I assume is the item marked TDA1034) on the 475 schematic
There are also two outputs.
It doesn't seem on a newbie inspection that there is any summing going on?
If so what is the 475 used for?

Doppel-Knötenpunktverstärker means "dual-summing-amp". Stereo.

Sorry for being so thick...
So the 475 is a dual summing amp

But each channel only has one input and one output - so the only thing that can be going on is bumping up the gain on each input and redirecting that to the same output.

I know this is simple for you guys - but what have I missed?

Okay - I am starting to get this....
If this were in a console you would have multiple channels feeding the inputs
And each channel would have it's own gain set on the channel strip itself (thus affecting the value of RK being sent to teh summing amp)

So the box is adding gain to the inputs via the setting of RG

So onto the next question...
Rather than use this as a summing amp (know that I know what one is) is there enough gain here for a mic preamp mod?

[quote author="uk03878"]Okay - I am starting to get this....
If this were in a console you would have multiple channels feeding the inputs
And each channel would have it's own gain set on the channel strip itself (thus affecting the value of RK being sent to teh summing amp)

So the box is adding gain to the inputs via the setting of RG

So onto the next question...
Rather than use this as a summing amp (know that I know what one is) is there enough gain here for a mic preamp mod?[/quote]

so did you build a summing amp with the v-475 by now?

[quote author="digichild"]so did you build a summing amp with the v-475 by now?[/quote]
mine is finished and in working condition, just needs to be racked and a PSU :grin:

Hi Silent Arts

Please post description of your project maybe even with photos :razz: :razz:
Cheers

Morten