my buzz fix method

[Joerg Reisenweber]

Am So  5. April 2009 schrieb Rask Ingemann Lambertsen:
> On Fri, Mar 27, 2009 at 03:34:00AM +0100, Joerg Reisenweber wrote:
> 
> > Regarding your low volume: did you check R4303? (It's the one below the 
two NC 
> > pads and right side to C4303, the one you borked and replaced. It's 
clearly 
> > mentioned in my SOP paper) R4303 is not mentioned in your story if I 
didn't 
> > miss anything. Usually it's 0R and it's amazing you get *any* signal at 
all 
> > from mic if you haven't replaced it by a ~2k2k (probably anything between 
> > 400Ohms and 3k will do, though I learnt by your report even a 0R will do 
at 
> > least partially :D  ).
> 
>    Joerg, could you clarify the significance of R4303 a bit? For example,
> how would I tell if it has 2.2 kOhms or 0 Ohms without measuring it (on a
> device without the buzz fix as well as with the buzz fix)?

Probing is the *only* way you can tell afaik.
We are basically grounding upper end of mic with a huge capacitor (AC), so we 
need some R >>0Ohms on the lower end of mic to get some signal at all.

> 
>    The 100 uF capacitor is just the C4306 which isn't installed by default,
> right?

Without checking for correctness of #4306 basically yes.

> 
>    MICBIAS is also supplied to the headset mic (location 44xx). Would it do
> any good to add a 100 uF capacitor somewhere in that area too?

Nope, for a number of reasons it won't work, just break function of hs-mic 
completely. See explanation some lines above. HS-Mic is singlen-ended (lower 
pin connected to GND)

/j
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