Add a DAC to a cheap CD player?
 

In article , Wally
wrote:
Jim Lesurf wrote:


Listened to on a Quad 67 the sound just got very vague and dull. (This
was using the Meridian DAC outboard from the Quad, so reading the same
data/errors in each case.) The Quad seems to try and 'hide' serious
losses by smoothing them over when the meridian seems to decide
"bugger it! I'd better let them hear this isn't right!" :-)

Vague and dull is more like what I get from the Schneider player.

It is therefore possible that this is due to smoothing over lost data.
However it may simply be that the frequency response is poor and is rolling
off the HF. Hard to say without some measurements, etc.


Pay yer money and take yer choice on which approach you'd prefer...

Given that I don't have a handy DAC with which to test my cheapie
player, I suspect it's more a case of paying my money and taking my
chance... :-)

:-) That does tend to be the way around - unless you can pursuade someone
to loan you a DAC on a 'try before buy' basis.


Afraid I can't really say. In normal use, my experience is that DACs
do not often make large differences once the system is essentially
decent.

That leaves me feeling that almost any external DAC is going to be an
improvement over the player's internal one. Which leads me to wonder if
something at the (very) cheap end of second hand would make a good
improvement.

I'm biassed, but my recommendation would be for an old meridian DAC as
these seem well engineered, and sound excellent to me. Other DACs may be
superb, though. Some makers do seem to engineer a specific 'sound' which
you may prefer.

I've noticed in my browsing that some are listed as doing 30-something
KHz, as well as 44.1 and 48, and assumed that some were designed to
handle different rates. I've been wondering if I should be looking for
something which will handle 48KHz as well as 44.1, as a future-proofing
thing, but I'm feeling now that 44.1 will be sufficient for a good while.

If you are going to play the sound from DVDs then 48kHz is required. Also
check that your DVD can be set to output S/PDIF, not just the 'bitstream'
for surround Dolby, etc. Older DACs can understand S/PDIF but not the
bitstream.

(BTW This is yet another multiple-use of a word as 'bitstream' has also
been used for something quite difference to its meaning in this context.)

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?
 

In article , Ian Molton
wrote:
On Wed, 10 Dec 2003 09:36:54 +0000 (GMT) Jim Lesurf
wrote:

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.

well, there comes a point where cumulative jitter is more or less the
same as either no jitter, or (effectively) a different than expected
clock speed (with resulting loss of bits if it goes on long enough).

This all comes down to how you view what is happening - phase modulation or
frequency modulation. :-)

a 'smoothed' clock would basically be a 'super long timebase PLL' (is
that what you were getting at there?)

In effect, yes. The 'new' local clock has a frequency that only changes
(relatively) slowly. This clearly has to be limited as if it is too slow
the system will get out of step and you'll risk problems like buffer
under/over-flows or bit-skipping somewhere. Within the scope of such
problems, a longer slower clock should be better. Clever systems adapt this
to the quality of the data, but I doubt any domestic DACs go beyond the
Meridian approachs. There are various ways to skin this cat. The main doubt
is to how much effort is worthwhile as the problem may be less in practice
than magazine articles might lead us to believe.

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?
 

In article , Ian Molton
wrote:
On Wed, 10 Dec 2003 09:36:54 +0000 (GMT) Jim Lesurf
wrote:

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.

well, there comes a point where cumulative jitter is more or less the
same as either no jitter, or (effectively) a different than expected
clock speed (with resulting loss of bits if it goes on long enough).

This all comes down to how you view what is happening - phase modulation or
frequency modulation. :-)

a 'smoothed' clock would basically be a 'super long timebase PLL' (is
that what you were getting at there?)

In effect, yes. The 'new' local clock has a frequency that only changes
(relatively) slowly. This clearly has to be limited as if it is too slow
the system will get out of step and you'll risk problems like buffer
under/over-flows or bit-skipping somewhere. Within the scope of such
problems, a longer slower clock should be better. Clever systems adapt this
to the quality of the data, but I doubt any domestic DACs go beyond the
Meridian approachs. There are various ways to skin this cat. The main doubt
is to how much effort is worthwhile as the problem may be less in practice
than magazine articles might lead us to believe.

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?
 

In article , Ian Molton
wrote:


Scenario 2: The two clocks are not a prefect match, the DAC clock is
either slower or faster than the data sources clock.

in this case, if its faster, it will (periodically) drain all its
buffering, no matter how much there is, and will end up stretching bits
to fill the gap (or playing silence, whatever)

This may be the case if there is no mechanism in the receiver to adjust its
medium/long-term clock frequency towards that of the transmitter. However
the S/PDIF stream has clock info encoded into it. Hence a receiver can use
this as it wishes to avoid the phases drifting too far if the designer so
chooses.

jitter is simply noise above, and will average out to nothing. If it
DIDNT cancel out, it'd effectvely be a frequency drift of the data
sources clock, which is no longer called jitter (duh).

The above treats this as a matter of terminology. In reality, both the
transmitter and reciver clocks will wander about in an apparently random
manner over all timescales of variation. The object then is to minimise
these wanderings and their effects.

I don't know if there is any official timescale defined in audio for the
longest term that is 'jitter' beyond which it becomes 'drift' of 'static
error'. Hence I'd be inclined to regard these as all facets of the same
problem and treat them accordingly.

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?
 

In article , Ian Molton
wrote:


Scenario 2: The two clocks are not a prefect match, the DAC clock is
either slower or faster than the data sources clock.

in this case, if its faster, it will (periodically) drain all its
buffering, no matter how much there is, and will end up stretching bits
to fill the gap (or playing silence, whatever)

This may be the case if there is no mechanism in the receiver to adjust its
medium/long-term clock frequency towards that of the transmitter. However
the S/PDIF stream has clock info encoded into it. Hence a receiver can use
this as it wishes to avoid the phases drifting too far if the designer so
chooses.

jitter is simply noise above, and will average out to nothing. If it
DIDNT cancel out, it'd effectvely be a frequency drift of the data
sources clock, which is no longer called jitter (duh).

The above treats this as a matter of terminology. In reality, both the
transmitter and reciver clocks will wander about in an apparently random
manner over all timescales of variation. The object then is to minimise
these wanderings and their effects.

I don't know if there is any official timescale defined in audio for the
longest term that is 'jitter' beyond which it becomes 'drift' of 'static
error'. Hence I'd be inclined to regard these as all facets of the same
problem and treat them accordingly.

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?
 

On Wed, 10 Dec 2003 14:45:27 +0000 (GMT)
Jim Lesurf wrote:


does it have an optical input?

Pass.

Apparently it does. I'll let you all know what I think of its output when it arrives ;-)

--
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 Wed, 10 Dec 2003 14:45:27 +0000 (GMT)
Jim Lesurf wrote:


does it have an optical input?

Pass.

Apparently it does. I'll let you all know what I think of its output when it arrives ;-)

--
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?
 

Ian Molton wrote:

On Wed, 10 Dec 2003 18:33:51 GMT
"Wally" wrote:

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).

Aye, a tad pricey. :-)

And, IMHO, the wrong solution to the problem. Can we say 'aliasing' ?

In an ideal world there would be a better way to achieve jitter
immunity, but all the reports that I've heard claim that the SRC is very
transparent and the unit is one of the best (transparent) sounding DAC's
around.

Cheers.

James.

Add a DAC to a cheap CD player?
 

Ian Molton wrote:

On Wed, 10 Dec 2003 18:33:51 GMT
"Wally" wrote:

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).

Aye, a tad pricey. :-)

And, IMHO, the wrong solution to the problem. Can we say 'aliasing' ?

In an ideal world there would be a better way to achieve jitter
immunity, but all the reports that I've heard claim that the SRC is very
transparent and the unit is one of the best (transparent) sounding DAC's
around.

Cheers.

James.

Add a DAC to a cheap CD player?
 

On Thu, 11 Dec 2003 10:06:03 +0000 (GMT)
Jim Lesurf wrote:

This may be the case if there is no mechanism in the receiver to adjust
its
medium/long-term clock frequency towards that of the transmitter.
However
the S/PDIF stream has clock info encoded into it.

Indeed. but we were discussing reclocking to a perfect clock, which
means the spdif clock is being replaced by one that is not even locked
to it, which will show the effects described (eventually)

Of course, if anyone owns such a system, I'll be happy to sell them a
'thermal clock recalibration and drift elimination tool' (aka, bunsen
burner and hotplate underneath), complete with soft rubber mouts and
counterweighted, balanced platform...

The above treats this as a matter of terminology. In reality, both the
transmitter and reciver clocks will wander about in an apparently
random manner over all timescales of variation. The object then is to
minimise these wanderings and their effects.

Indeed. of course, for the purposes of what I was explaining, its valid
to consider the transmitter clock as perfect and the other running fast
or slow (its the relative difference that matters :-)

I don't know if there is any official timescale defined in audio for
the longest term that is 'jitter' beyond which it becomes 'drift' of
'static error'. Hence I'd be inclined to regard these as all facets of
the same problem and treat them accordingly.

Agreed :-)

--
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.