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Subject: Re: Recorder noise
From: Björn Stenberg (bjorn_at_haxx.se)
Date: 2002-02-16

Andrew Jamieson wrote:

> * If the noise goes away when the music is stopped, then it's not the amp
> that's causing it, but the pre-amp.

There are actually two levels of noise. One louder during playback and one
quieter that is always present when the unit is turned on.

> If the noise is of a very low frequency (such as 15hz) then the Archos may
> be missing the higher rated caps (uF).

The noise itself is more or less white noise. The 10-15 Hz I was talking about
is the oscillating changes heard in the noise while displaying the VU meters,
sounding "dzi-dzi-dzi-dzi" at a rate of approximately 10-15 "dzi" per second.

> * The schematic does not show a capacitor to PVDD. This is an auxilary
> supply to the analog circuitry, and is specified as requiring a 3nF bypass
> cap to AVDD1. It's possible that hooking this up would help ....

In one of the photos on the Yahoo group page I can see pin 63 (PVDD) is
connected to one side of a tiny component, probably a capacitor, and pin 64
(AVDD1) is conntected to the other side. Here's the URL (you have to register
with yahoo):

http://photos.groups.yahoo.com/group/archosjukebox6000/vwp?.dir=/Jukebox+Recorder+inside&.dnm=main+top.jpg&.src=gr&.view=t&.hires=t

> * The input lines on serial audio input (SIC, SID, SII) are left floating.

In the above photo, pin 45 (SID) is connected to something marked "103" while
pin 46 and 47 (SII and SIC) are indeed unconnected or routed under the chip. 

-- 
Björn

Page was last modified "Jan 10 2012" The Rockbox Crew
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