Audio, hi-fi and car audio - Add a DAC to a cheap CD player?

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Add a DAC to a cheap CD player?

"Wally" wrote in message
...
malcolm wrote:

Silver-fronted jobbie. Asda were flogging them for £100 a few months
ago. Last seen at 70 quid before disappearing.

Wal-Mart sell Apex ones for 45 dollars or so, would be about 30 quid
in the UK.
and post Thanks-giving day sale they were $29.95 for a morning.
they have one playing movies on a TV and quite good pic quality.
silly prices now, don't know what the postage would be from the USA
to the UK,
and whether the customs would slap import duty on one.

I already have a player - I'm looking into improving it with a DAC.

--
Wally
www.art-gallery.myby.co.uk
Latest work: The Langlois Bridge (after Van Gogh)

just comparing price differences etc

Add a DAC to a cheap CD player?

On Wed, 10 Dec 2003 03:04:30 -0000
Jim H wrote:

I wonder - would the DAC ensure the discarded bits are the least
significent ones?
If so wouldn't the worst reclocking can do just lower the resolution from
16 to 15
bits for 1/44000 of a second?

You tell me. I dont know what the DACs are doing internally.

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

Add a DAC to a cheap CD player?

On Tue, 09 Dec 2003 16:53:29 +0000 (GMT)
Jim Lesurf wrote:

For my taste the Meridian DACs seem excellent.

Do you know anything about the ARCAM Delta black box 3?

does it sound good?

does it have an optical input?

--
Spyros lair: http://www.mnementh.co.uk/ |||| Maintainer: arm26 linux

Do not meddle in the affairs of Dragons, for you are tasty and good with ketchup.

Add a DAC to a cheap CD player?

In article , Ian Molton
wrote:
On Wed, 10 Dec 2003 01:15:00 GMT "Wally" wrote:

So, what's the difference between async and reclocked? If reclocking
is about feeding back time adjustment info from DAC to transport, does
asynchronus mean there's some sort of buffering in the DAC?

thats not reality, sorry.

the 'reclocked' signal is simply one that has been resynchronised to
another clock, with bits added / discarded to suit the difference in
clock speed between the spdif clock and the reference one.

neither this or what I called 'async' above has any feedback at all.

Alas, this is an area where most of the terms used have become ambiguous or
vague due to being used by marketing types to mean different things in
different cases. Hence terms like 'reclocked', 'upsampled', etc, should now
be treated with caution. :-/

The S/PDIF data stream contains its own 'clock info' mixed in with the
signal. A reciever (DAC) can if it wishes seek to 'recover' this clock
info, and then use it to control its own 'local clock'. Methods for doing
this vary, but the obvious one is a phase lock loop. It also tends to imply
some data buffering in the receiver to give the clocks some elbow room to
get out of timestep without data loss, and to give a longer running average
time for the local clock smoothing. However all these details will depend
entirely upon how a given receiver was designed/built.

In the absence of any attempts to 'fiddle with the clock', the most basic
approach would just read in each (serial) digital value (stereo pair), and
then when it arrived, shove it through the system and output a fresh
analogue level. However this would mean that any irregularities in timing
will modulate the output.

By having a subsystem that looks for the clock info in the input stream,
and use this to control a local clock, you can output data at a (nominally)
smoother rate. This can only deal with 'short term' variations, though, and
where the size of the jitter is reasonably small. Nor can it entirely
remove any effect, just reduce them to some extent.

DACs like the Meridian ones apply control loops to read in the data, and
then play them out under the control of a 'smoothed' local clock. This can
reduce the effects of jitter provided the input isn't too bad. Other DACs
may use various methods (or none at all) to try and deal with this. When I
first bought a Meridian DAC I assumed that all DACs did this, and used the
methods I'm familiar with from data comms. However I was surprised later on
to be told that they did not.

'Upsampling' and some other terms are really about addressing another area.

Whether jitter is a significant - i.e. audible - problem in most cases is
another matter. I like the Meridian DACs, but have no idea if 'jitter
reduction' has anything to do with that! :-)

Slainte,

Jim

--
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Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Add a DAC to a cheap CD player?

In article , Jim H
wrote:
On Wed, 10 Dec 2003 02:12:49 +0000, Ian Molton wrote:

On Wed, 10 Dec 2003 01:15:00 GMT "Wally" wrote:

So, what's the difference between async and reclocked? If reclocking
is about feeding back time adjustment info from DAC to transport,
does asynchronus mean there's some sort of buffering in the DAC?

thats not reality, sorry.

the 'reclocked' signal is simply one that has been resynchronised to
another clock, with bits added / discarded to suit the difference in
clock speed between the spdif clock and the reference one.

I wonder - would the DAC ensure the discarded bits are the least
significent ones? If so wouldn't the worst reclocking can do just lower
the resolution from 16 to 15 bits for 1/44000 of a second?

Alas, the DAC has no real control over what bits might be lost due to
jitter, or noise. These problems are not under its control at source.

To minimise this effect components should be placed side by side, not
stacked. Most hi-end gear was not designed to handle the effects of
relitivity.

Eh?

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Add a DAC to a cheap CD player?

Wally wrote:

Judging by the prices that DACs are going for, I'm thinking that this would
be a good improvement over the existing setup for less than the cost of a
comparable player. My mate's £500 Arcam player has quickly established
itself as something of a benchmark - I'd like to approach, or improve on,
that sort of quality if feasible. My thinking is that, when my existing
player starts to bite the dust, I could look at getting a transport that can
take a timing signal from a DAC. Is it a standard signal for all (most?)
transports/DACs, or is it rather proprietary?

I'm sure an oscilloscope is a much cheaper approach... ;-)

Actually, he's being coy. 'Better kit' in this case most certainly
does *not* include DACs which can't suppress jitter in the datastream,
but they certainly cost a lot of money, and they do sound bad! :-)

Do you mean DACs that use a sync signal to control jitter, as opposed to
those which can take a raw datastream and make the best (or better) of it?
Would a DAC which has a sync output and a bunch of oversampling be the right
thing to go chasing after?

The best value for money in jitter immune DAC's is reputed to be the
Benchmark DAC1 which uses a sample rate convertor in front of the DAC.
It is a little out of your price range at $850 (no UK distributor
either).

I'd forget about word clock outputs for your purpose - very few CD
players can actually use them.

Cheers.

James.