[sdiy] [OT] Mixer upgrades

[Terry Michaels]

Hi All:

I recently picked up an '80s vintage Soundcraft model 200 SR mixer which I
intend to use for recording purposes.  A look inside shows film type 2%
resistors with either a blue or violet body color used throughout the unit.
 Does anyone know if these are carbon film or metal film?  It's generally
known that metal film resistors generate lower internal noise than carbon
resistors, if these are indeed carbon resistors, is it worth the trouble of
changing them out with metal film resistors at least in the front end (mic
preamp) section?

The front end uses a 2SA1316GR differential pair feeding a TL072, any need
to upgrade this area?

Electrolytics are known for being less than perfectly linear, so is there
any benefit in adding disc or film caps across the numerous electrolytics
in the audio chain? 

Schematics for this mixer are available at the Soundcraft web site, in case
anyone wants to have a look at the circuitry.

Terry Michaels