Mic preamp for dynamic mics, any glaring errors ?

[00940]

Laying down the thing on pcb brings a new question... I can easily do it single sided (the following layout is 40mm/80mm, top "tracks" are jumpers, left side is input, right side output and PS input). But should I pour a groundplane as shield on top ? And if I do, where is it best to tie it ? At the PS input ground pad, at the star ground ?

 

[MarcelvdG]

I would tend to use a ground plane and connect it everywhere, using lots of vias, and keep only parts of the supply that conduct large 50 Hz or 100 Hz ripple currents isolated from the plane. This should give you a nice low-ohmic ground for low frequencies as well as RF interference. But then again, I haven't got much PCB experience.

 

[00940]

Just for the record: here are the values needed for a 12-positions rotary gain switch, with 5db steps. A 100k or so in parallel might be a good idea to avoid random behavior in between steps if using a non-shorting switch. Resistors values were calculated with r2 as 10r.