Re: Audio circuit : pcb layout impact

From: Pooh Bear (rabbitsfriendsandrelations_at_hotmail.com)
Date: 10/20/04 

Date: Wed, 20 Oct 2004 04:17:20 +0100

Joerg wrote:

> Hi Sylvain,
>
> The main thing I'd do is provide a nice full ground plane. You don't
> want any of the data noise to show up in the audio path. That would be
> my biggest concern. Trace widths for the signals aren't that critical as
> long as the traces don't meander through digital territory too much.

Generally agreed.

Depending on the chips, you may actually want to separate the analogue and
digital ground planes and connect them at a known point of low noise ( such
as a power supply common terminal ). I tend to do it this way and it works
well. It keeps digital noise currents out of the audio path.

Some converters nicely adopt a pinout that allows them to 'bridge' these
planes with digital one side and analogue the other.

> Also, provide enough bypass caps.

Beware - 'bypass caps' can inject supply noise current into the ground.

Keep the values small ( as little as say 22nF ) and very local to the chips.
Far too may ppl use excessively large 'decoupling' for no good reason.

Graham

Relevant Pages

  • Re: PCB Layout (for ADC and DAC)
    ... How much noise will be introduced? ... also when not using these special precautions such as a ground plane? ... that the circuit could actually not function properly rather than just ... The important number is the gain * bandwidth value. ...
    (sci.electronics.design)
  • Re: PCB Layout (for ADC and DAC)
    ... I'm curious as to just how bad not having a ground plane is. ... How much noise will be introduced? ... I assume that the issue is with the analog domain or is there a reverse ... that the circuit could actually not function properly rather than just ...
    (sci.electronics.design)
  • Re: PCB Layout (for ADC and DAC)
    ... I'm curious as to just how bad not having a ground plane is. ... How much noise will be introduced? ... I assume that the issue is with the analog domain or is there a reverse ... that the circuit could actually not function properly rather than just ...
    (sci.electronics.design)
  • Re: Texas TMS1232 Delta Sigma converters
    ... Use SMT bypass caps at all supply pins, right from pin to ground plane, no wires. ... Bench power supplies can exhibit huge noise levels. ...
    (sci.electronics.design)
  • Re: HDDVD and Blu Ray
    ... The reality for me is that every analogue TV system I've ever watched ... for the image to have ghosting blurring the image and visible noise. ... (on the other hand PAL cross colour is always there! ... reducing resolution or introducing motion artifacts probably. ...
    (uk.rec.audio)