[sdiy] [OT] Mixer upgrades

[Tony Clark]

   Hi Terry,

> 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?

   Metal film resistors are usually coated blue or green or some 
variation thereof.  While carbon resistor tend to look like brown 
cylinders with sharp edges, metal-film resistors are usually hourglass 
shaped and/or have very smooth rounded edges.  I also don't recall 
carbons coming in anything better than 5%.  However, there were certainly 
techniques to get them there.  :)


> 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? 

   No, but it may be a very good time to recap the mixer!  Replace all of 
the electrolytics with low ESR types.

   Good luck!

   Tony

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