View Full Version : Squeezebox/External DAC - audio quality

Simon Turner
2004-03-18, 19:21
My findings are not too similar I think.
I use a high end Naim system with Shahinian Arc speakers. This is a system
that all too readily exposes weaknesses in the audio source. If I had a less
precise system then my experinces could possibly be very different.

I will not bother with MP3 comparisons as MP3s lack full bass and full
brilliance (whatever quality the rip is) on this system (fine on my other
lower and mid end systems though). However, I am willing to concede that
it's possible that this may only be noticeable with very detailed music with
modern high production values.

If it matters (which it might, I don't know) I compare using modern
electronic music that delights in deep bass and complex synth sounds (such
as that found on the Twisted and Ultimae music labels for instance).

Using Flac files...
Comparisons between the analogue-out of the SB and my Naim CDX are quite
hard to do as the low ouputlevels of the SB mean that to compare I have to
adjust the volume levels on my pre-amp as I switch between the two devices.
However the SB output does apear to be a little duller and lack some of the
the complexity, detail and brilliance of the Naim CDX. This is not a
surprise as the CDX is quite expensive, and for the vast majority of users
will not present a significant enough difference in quality to worry about,
(i.e. the SB DAC is pretty good really).

I bought a cheap Arcam Delta Black Box 5 DAC (100 UK Pounds)from eBay to see
if it improved upon the sound offered by the SB analogue-outs. It does,
quite appreciably. The comparison between it (playing Flac files) and the
original CD is made simple as the output levels (volume) of the CDX and the
DAC are eaxactly the same, so I just played the CD at the same time as i
played the Flac rip of the CD and continually switched between the two using
the Naim pre-amp. I observed that the Arcam Dac sounds marginally muddier
and less precise than the CDX in the upper lower to lowver middle
frequencies, but that was almost about it. It thibk is possible that if i
bought a reasonable DAC then I would be able to improve upon the CDX.
Current second hand cost of the CDX is about 1000 UK pounds (I think it may
have been sold new for over 2000 to 2,500 UK Pounds two or three years ago).

I should point out that the Arcam does not generally Sync Lock with the SB,
but when it does (only 10 seconds at a time, very occasionally) I have not
immediately noticed any difference in sound quality.

Generally when playing a CD the transport and the DAC have the greatest
effect on the final sound (apart from your choice of amp and speakers, and
the fact that CDs are pretty crap, obviously). The CD transport can do a
fair bit of guessing at the sound on the CD as it has to deliver it's
interpretation of the sound on the CD quick enough for the listener to hear
it. Ripping to Flac takes this out of the equation. Then you are left with
the DAC. External DACs are really cheap second hand at the moment. The
majority of second hand DACs for sale are far superior to those included in
dedicated CD players.

If the Squeezebox had a few fundamantal flaws ironed out it should make your
CD player redundant (from an audiophile point of view). These flaws (for me)

1) Sound drop outs (detailed in thread: "Squeezebox: Sound drop out with
Flac files")
2) Lost connection with Slimserver (detailed in thread: "Problem: Lost
contact with Slimserver").
3) Synchronisation with DAC clock (although i am not convinced that this
makes a any difference to the sound quality at all, but cannot conclusively
test as my SB will only currently stay synchronised for 10 seconds in a blue

Simon Turner
Brighton UK

> -----Original Message-----
> From: discuss-bounces (AT) lists (DOT) slimdevices.com
> [mailto:discuss-bounces (AT) lists (DOT) slimdevices.com]On Behalf Of Mark Bennett
> Sent: 17 March 2004 22:46
> To: discuss (AT) lists (DOT) slimdevices.com
> Subject: [slim] Squeezebox/External DAC - audio quality
> Tonight we tried again to connect the Squeezebox up to an
> external DAC with a high end sound system behind it.
> The sound system consisted of:
> Audio Synthesis DAX external DAC
> Naim Pre-amp (don't know which one)
> Naim Power amp (ditto)
> Pair of very large KEF Floorstanding speakers (ditto)
> We had some technical issues which meant we could only try
> with MP3 encoded files (see "Squeezebox/External DAC -
> technical issues" thread). However, these were encoded with
> Lame at 320kb/s, and also with the quality=0 setting
> (supposedly best quality). This was disappointing, since I
> was all setup to try Flac streams......
> Secondly, we also did not do blind testing. Just simple A/B
> testing. I fully accept that this is not a completely reliable
> comparison route, and once we have Flac working properly we
> will try proper (double) blind testing.
> All that considered the audio quality was extremely good. The
> two main differences were a difference in base extension, and
> a slight lack of precision in the sound. I'll explain what
> I mean by these statements below, but I just want to make one
> comment first.
> The quality from the Squeezebox/DAC under this scheme was
> pretty damn good. It was significantly better than my current
> system at home, and my audiophile friend pronounced that it was
> good enough to listen to all day. Generally well done to the
> Slim Team.
> So, what does "lack of bass extension" mean? When listening
> to the same tracks, with plenty of bass content, you could
> actually feel the low notes coming through the floor. With
> the SQ/MP3 combination this really low frequency bass just
> wasn't there. We both fully believe that this is entirely
> due to the MP3 encoding rather than any SB issue. The bass
> that was there (certainly more than my home system can
> replay) was pretty good (subject to my next comment).
> Now onto "lack of precision". This is a bit more subjective
> but many aspects of the sound just weren't quite as clearly
> defined as when coming from the CD transport through the
> same DAC. The two key points here are that the instrument
> location in the soundstage wasn't quite so accurate and
> that the timing didn't seem quite so precise. Sharp drum
> beats from the CD became slightly extended and slightly
> merged into each other rather than being discrete beats.
> In context all of these are a pretty fine points, and the
> difference was small enough that given more time we should
> have tried blind testing to see if it was really there. I
> also suspect that most (if not all) of this was caused by
> the MP3 coding rather than any other effects, but we can't
> yet conclusively rule out clock jitter here. Once we get
> Flac/Wav decoding working we should be able to take the lossy
> encoding out of the equation and truly compare like with like.
> In summary, it's starting to look like the SB has the
> potential to replace a serious CD transport in a high-end
> system.