Re: gEDA-user: buzzing board

[Steve Meier <smeier@xxxxxxxxxxxxxxxxxxx>]

1) Have you put a "reasonable" 16 ohm load across the speaker pins of
U302 and U303?

2) The datasheet for TDA7056 shows a 5K resister between the input pin
and ground.

3) from the dac to the speaker drivers you have an R C could you be
getting a parallel inductance back through ground? Try shorting out C304
and C305

4) The gain control circuit is interesting to say the least. You might
isolate its output pin and ground the signal ground to ground. Also the
MPC6001 datasheet has an example of 45 degrees phase margin when driving
a 500pF load. But the TDA7056 data sheet fails to mention its input
capacitance. Also you gain capacitance and inductance from the MPC6001
to the speaker drivers. I might be tempted to put a small resister and a
capacitor just before the speaker drivers.


On Thu, 2007-09-13 at 20:08 -0700, Steve Meier wrote:
> can I see a bom or schematic?
> 
> On Thu, 2007-09-13 at 22:27 -0400, DJ Delorie wrote:
> > > also re-read the data sheets any chance you tied a reference output
> > > to ground?
> > 
> > Which chips would have these?  The OLED has a few pins that "must
> > remain floating" and they're floating.
> > 
> > 
> > _______________________________________________
> > geda-user mailing list
> > geda-user@xxxxxxxxxxxxxx
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> 
> 
> 
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