Rockbox.org home
release
dev builds
extras
themes manual
wiki
device status forums
mailing lists
IRC bugs
patches
dev guide



Rockbox mail archive

Subject: Getting rid of that damn noise.
From: Justin Fisher (jaf60_at_it.canterbury.ac.nz)
Date: 2001-12-27


I'm just skimming though some of the incredible work you guys have done
(the entire archos circuitry mapped out - amazing! Even if I can't
follow most of it :-), and my thoughts return to finding a way to get
rid of that annoying background hum in the AJBR (the one that ceases
whenever the JBR accesses the HDD, thus we know it is possible for the
JBR to play mp3's without the noise).

Seeing as there are only four lines coming out of the CPU to operate the
LCD (the LCD system seems to be the culprit as the hum frequency matches
the screen updates, goes silent when the screen freezes (ie during HDD
reads) yet the CPU is presumably active during this silence), I was
wondering if anyone wants to, er... cut them. :-)

I figure that adding a switch to your unit that simply switches off the
LCD section, and thus switches off the background hum, would be a great
modification. And pretty easy to do. UI-wise, it is virtually no effort
to flick the LCD back on if you want to check something, and when you're
listening, you're not looking at the LCD screen anyway. Awesome sound
quality at the flick of a switch. That is assuming my layman deductions
hold water and the noise is indeed eminating somewhere between the LCD
screen and the CPU.

Does it sound like something worth investigating? If removing the noise
was as easy as installing a switch on the CPU outputs that go to the
LCD, I'd be overjoyed.
If it is that easy, would there be complications? (ie components not
liking being hot-plugged like that, or several other lines also needing
to be switched? Would simply cutting the power to the LCD driver (a mere
one line) and leaving the CPU data lines connected suffice?

Thoughts?
Barking up the wrong tree?



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