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View Full Version : Frequency drift when going from MP3 to WAV



Michel Fombellida
2004-04-22, 15:05
Hi,

I have currently 5.1.5 and firmware 10 but I've noticed the following
behaviour since at least 5.1.1: at the output of the SB I have a system
(Apogee Big Ben) that shows me precisely the frequency of the signal that the
SB delivers. When the SB plays an MP3 file the signal immediately locks on
44.10 khz but when I swap from MP3 to a WAV file, the signal jumps to 43.95khz
and then starts slowly drifting to 44.10 but I would say that it takes more
than 10 seconds before it reaches 44.10. During the drift, my system looses
the signal and I have to put the SB on pause to allow it to reach 44.10. Once
it is on 44.10 I can play WAV files perfectly (and it stays there as long as I
play WAV files), if I swap back to MP3 then it also stays on 44.10 but then
when I again go back to WAV it again goes back to 43.95 and starts slowly
drifting once again.

Any idea what this could be, any way to fix that to make the SB lock on to
44.10 with WAV file as fast as it is for MP3?

Cheers,
Michel

Michel Fombellida
2004-04-22, 23:34
Hi,

> Any idea what this could be, any way to fix that to make the SB lock on to
> 44.10 with WAV file as fast as it is for MP3?

By the way, I know 2 other users with a similar setup (Apogee Big Ben) who
noticed exactly the same.

If I can be of any help testing something, just let me know.

Cheers,
Michel

seanadams
2004-04-26, 00:58
I can confirm this - at first I thought it was just the way my
frequency counter worked, but then I noticed that it doesn't happen
when going to mp3 mode. The PLL (circuit inside the DSP which generates
the audio clock) is just taking much longer to stabilize... but it does
stabilize, and once in PCM mode it's just acting as a passthrough so it
doesn't even see song transitions (so it stays locked). Anyway I will
see if I can find out why it does this - our goal of course is to be
able to switch formats as seamlessly and quickly as possible.

On Apr 22, 2004, at 11:34 PM, Michel Fombellida wrote:

> Hi,
>
>> Any idea what this could be, any way to fix that to make the SB lock
>> on to
>> 44.10 with WAV file as fast as it is for MP3?
>
> By the way, I know 2 other users with a similar setup (Apogee Big Ben)
> who
> noticed exactly the same.
>
> If I can be of any help testing something, just let me know.
>
> Cheers,
> Michel
>
>
>
>