[sdiy] Length of a summing node (was Re: AC coupling caps on MS20 clone)

[Neil Johnson]

Hi,

Mixing desks have physically long op-amp input rails - the so-called  
'busses'.  However, the physical layout plays a huge role in ensuring  
a low noise result.

Impedances vary - but they're usually around a few kilo-Ohms (Seck  
used 10k input resistors, Mackie 1604 has 5k1 with considerable  
effort in grounding too).  The lower the impedance the lower the  
noise, but then the op-amps needs to be able to push more amps and  
not distort to give any improvement (or is a trade-off of noise vs.  
distortion?).

Neil
--
http://www.njohnson.co.uk