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Julian Alden-Salter
2005-03-01, 05:09
Robin,
Unfortunately, I'm pretty new to the world of modifying components - until
recently I was blindly climbing the Naim upgrade ladder. This means I don't
have any way of measuring jitter at my disposal.
Also the transports were brought round to my place where I hosted what is
commonly known as a 'bakeoff' where we all sit down and give other peoples
kit a listen at one place.
I would love to know what is going on between flac and mp3 - I've e-mailed
slim devices about this a couple of times and they've given me some
suggestions but nothing has helped. I doubt it's a high priority for them
as, as someone else pointed out, only about 1% of squeezebox users are going
to be fussed.
As I said I'm going to be trying a lightly modded roku in the near future so
I'll post the results of that one. The other thing I was wondering was
whether the pc used as the server would have any impact on things - I was
going to try switching to linux to see if that made a difference.
If none of the above make any difference then I'll be looking for an
appropriate case to re-house the squeezebox in, in order to re-clock it. I
know there is a high end transport hidden within the squeezebox dying to get
out.
Cheers

Julian.

-----Original Message-----
From: Robin Bowes [mailto:robin-lists (AT) robinbowes (DOT) com]
Sent: 01 March 2005 09:53
To: discuss (AT) lists (DOT) slimdevices.com
Subject: [slim] Modifying squeezebox clock

Julian Alden-Salter wrote:
> Robin,
>
>
>>What difference do you hear?
>
>
> Without launching off into audiophile rambling about 'inner detail' and
> 'timbre'. The dpa just sounded more realistic, detail was easier to hear
and
> transients (i.e. drum strikes) had more impact whilst the squeezebox
sounded
> muffled in comparison.

That sounds like classic symptoms of jitter - smearing of the transients.

> I'd have no qualms about trying to discern the
> differences in a double blind test and I'd be pretty damn confident that
I'd
> be able to get a statistically significant result telling the two apart.
To
> give myself a bit of leeway with hyperbolae - the difference was like
night
> and day. The fact that 4 of us were in total agreement (even though the
> tests were sighted and we all have wildly different tastes in music and
> systems at home) should give some clue as to the magnitude of the
> difference.

Have you got anyway to measure jitter? If so, you may be in a position
to perform an experiment to keep Phil happy :)

Something like this:

1. Measure jitter from Squeezebox
2. Measure jitter from the dpa
3. Perform double-blind testing between the two sources

I'd be very interested to hear about the results of such an experiment.

>>Erm, mp3s are lossy so they will inevitably sound "worse". How are you
>>comparing?
>
>
> I'm not actually talking about sound quality here - flac/pcm still has the
> legs on mp3 (just at 320 but it's a tough call at that bit rate). As I
said
> before my dac has low and high quality locks - one for high jitter signals
> which isn't very picky and can lock onto pretty much any standard digital
> signal you throw at it. There is also a higher quality lock which will
only
> 'XLOCK' if the signal received is low enough jitter / high enough quality.
> Mp3's and the transports tested all 'XLOCK'ed. Flac / pcm's do not. This
is
> 100% verifiable and consistent and not subject to any subjectivity - I can
> post pics somewhere if you like.

So, you're saying that the SB digital out is different for flac vs. mp3,
and that your dac will only XLOCK onto mp3s (and the output from your
other transports)? That is certainly interesting information. Can you
measure the jitter in the output when playing mp3s vs playing flac/pcm?

>>I've got to say, the Tent clock chip upgrade looks very appealing. I'm
>>planning an upgrade to my Art DI/O (4 x ALWSR PSUs: +/-15V, +5V digital
>>and +5V analogue) and I might slip a clock chip upgrade in too.
>
>
>>Let me know how you get on.
>
>
> I'm going to be borrowing a prototype alwsr psu specifically designed for
> the squeezebox in the near future. I'm not sure how big a difference it
will
> make as I feel a psu will mostly benefit the analogue output stage. I
tried
> a monarchy dip reclocking device but this made little or no difference so
it
> looks like the tent clock will be my next thing to try but the casing
issue
> makes things difficult.

Yeah, you need to pull the guts out of the SB and mount it in another
case if you're doing this level of modification.

I haven't decided exactly what I'll be doing, but one option is to build
the SB and the digital stage of my Art DI/O into a new chassis, along
with several ALWSR (I'll need five, or six if I add a Tent clock!)

That's on the back-burner right now until after I've moved house/changed
jobs. I'm going to work for Farnell so I'll great access to components :)

R.
--
http://robinbowes.com