View Full Version : Digital Output

Ken Hokugo
2005-03-03, 13:14
Mike, Michel, Sean, and other PCM and clock precision lunatics...

The first time I tried SB digital output to Big Ben input, I experienced the
same, but only when SB is just powered up. SB's digital output starts from
44.13, then gradually down to 44.10, and locks. Sure, the lock was/is
"fragile", but I thought it was OK.

Once I got my SB, and external PS for it, back from the person in France
(see Michel's post), I would start using Big Ben as a clock generator to
sync SB and DAC (in my case, TacT RCS). Looking forward to the result.


From: Mike Reeve <reeve_mike (AT) hotmail (DOT) com>
Reply-To: Slim Devices Discussion <discuss (AT) lists (DOT) slimdevices.com>
To: discuss (AT) lists (DOT) slimdevices.com
Subject: [slim] Digital Output
Date: Thu, 3 Mar 2005 16:21:30 +0000 (UTC)


Regarding problems with lock on external DACS ...

About a year ago it was found that the Squeezebox digital output was
somewhat off 44.10KHz BUT ...
.... Sean quickly [as usual!] fixed this in the firmware.

Fortunately I have always routed Squeezeboxes via a
device that buffers the input in a FIFO
and then clocks it out using its own high-precision, lower jitter clock,
so any such inacurracy has never been a problem for me.

However, out of curiousity I yesterday connected a Squeezebox
to an Apogee Big Ben and it registers the Squeezebox at 44.13KHz :-O

[Another long-term issue has been the long settling time of the clock
when switching into 'PCM mode' so I left the Squeezebox on repeat
all night so that this was not an issue ...]

So, I'm wondering why the 44.13KHz:
(a) Has the firmware changed?; (b) Is this 'manufacturing variance'? :-O;
(c) ...

Clearly 44.13KHz is way out of the range of some 'high-end' DACs
(e.g. AudioSynthesis DACs have a capture window of only +/- 100ppm
- approx. 4Hz),
so this could be the cause of some peoples' lock problems.

I know other people who read (or at least read) this list
(such as Michel, Harry & Victor from the TacTHackers group)
have both Squeezeboxes and Big Bens
- what do you guys (or anyone else having the two) see as frequency
these days ...?