A high quality CD Player
- Thread starter naimplayer
- Start date
Purité Audio
Trade: Purite Audio
Dave thanks for the advice, but there are heaps of places who will sell you stuff that does not improve sound quality, I am just not one of them.
@ Rad think about data transmission protocols .
Keith
radamel
Music Fiend
Have you ever heard about jitter and timing precision?
I hope you've just failed at trying to be funny.
venton
pfm Member
It is true that the cheapest cd laser will read 100% accurate data, the same as a more expensive one. But that's not the whole picture. The cd transport isn't just the head, it is the surrounding electronics as well.
In my opinion, the tiniest differences in the electronics, from the wires, the capacitors, transistors, vibrations etc will have some effect on the sound. If the components are slightly more noisy, this can have an effect on the noise floor of connected equipment.
The effect is not to affect the ones and zeros, but to effect the resultant analogue sound we hear. This is why listening is so important.
In my opinion, the tiniest differences in the electronics, from the wires, the capacitors, transistors, vibrations etc will have some effect on the sound. If the components are slightly more noisy, this can have an effect on the noise floor of connected equipment.
The effect is not to affect the ones and zeros, but to effect the resultant analogue sound we hear. This is why listening is so important.
radamel
Music Fiend
Are you saying that all you sell improves sound quality?!?!
About data transmission protocols... Care to elaborate?
DevillEars
Dedicated ignorer of fashion
Oh good... Here we go back in time to the early 1980s when everyone ran around shouting that "bits are bits" so all CD players will sound the same..
Since those early days "science" discovered that it did not know everything there was to know about digital audio in general and, in particular, the problems inherent in the Red Book CD standard.
The first "discovery" was that the stock sampling rate of 44.1KHz AND the use of a brickwall filter at ~22KHz introduced aliasing which was "nasty". This discovery led to the development of oversampling which saw the digital data stream sampling rate boosted by up to 8x the original 44.1KHz (just over 350 KHz) so that the aliasing frequency range was lifted far enough above the human hearing range for anti-aliasing filters to have less impact on the audible range.
The next aspect that was "discovered" was that the timing of the data in a digital data stream could - out of whack - cause unpleasant artefacts in the sound reproduced. These digital timing errors were labelled "jitter" and any jitter value above a certain level was BAD. Manufacturers leapt in and made design changes to reduce jitter to as low possible.
Bit accuracy (or a 100% correspondence, at bit-level, between data signal retrieved from CD drive read to data signal received at DAC input) was also predicted before production and error-correction circuitry was built-in to reduce the incidence of bit "drop-out" - "reduce", not "eliminate".
I could go on, but those are enough to illustrate the point.
The first CD players in the early 1980s promised "perfect sound forever" and delivered a sound quality that was distinctly unpleasant.
Comparing some of the better budget players of today against any early 1980s CD player (irrespective of their price-point) and you'll find that today's CD players offer better sound than those old ones.
Decent engineering in any audio component will not always provide any clear improvement in SQ over the unit's predecessor, but what decent engineering will provide is a combination of a decent product lifespan, better sub-component compatibility and a consistency of performance across multiple units (i.e. fewer instances of a "Monday hangover unit").
Decent engineering also takes into consideration "materials science" and it's this engineering approach that provide overall quality improvement - not just some arbitrary whinge about magnesium having been chosen as the appropriate material for what is a very costly transport mechanism.
The role of a proper engineering approach to design and build is probably best illustrated in the area of turntables - the LP12 was one of the early examples of where engineering was applied to audio build. Nowadays, one just has to look at all the really high-end turntables (TW Acustic, Caliburn, SME, Avid, VPI, etc.) and the stand-out aspect that is common across them is the standard of engineering employed.
A CD player also relies on a rotating disk (like vinyl) but that's where the similarity ends.
A record player's turntable must rotate at a stable angular velocity (measured in RPM) and this stable rotation must be accurate to the standard to ensure pitch accuracy.
A CD player's disk platter must also rotate at a stable velocity - but this velocity must be a linear velocity so that the data read from the disk is read at a stable data rate.
What this requirement does to CD mechanism design is to introduce the need for the disk to rotate at a variable angular velocity (RPM) where the position of any track being read from the inside edge is factored in to the motor speed control so that the circumference at track (in centimetres) is spun past the pickup at the desired linear rate (cm/sec) and that, coupled with the recording density (bits/cm) provides a data rate in bits/sec that must adhere to the spec as defined in the Red Book.
This variable rotational rate introduces the first level of complexity into CD mechanism design - the need to constantly adjust the rotational speed based on the position of the laser pickup along the radius of the disk (which is done via complex feedback circuitry which relies on accurate data on the track position and real-time rotation speed.
The accuracy required in the feedback data is crucial to the accuracy of the data stream output to the DAC and accuracy is best achieved via sound engineering...
Enough...
Dave
adamdea
You are not a sound quality evaluation device
Whaleblue
Southbound
Quite
Purité Audio
Trade: Purite Audio
LP12 and 'engineering' in the same sentence! EMT or Technics Sp10 now that's engineering.
Keith.
Keith.
radamel
Music Fiend
Have you missed my post above Keith?
Purité Audio
Trade: Purite Audio
Keep thinking Rad, you will get here.
Keith.
Keith.
radamel
Music Fiend
Purité Audio
Trade: Purite Audio
Ok three letters starts with A.
Keith
Keith
radamel
Music Fiend
A*S?
Suggest you forget CD players Devil - a modern recording exists as a computer file. I can either download that file, rip it off a CD or get it via a USB, DVD, flash card etc etc. If the data is the same all the angular velocity in the world won't change it. And if bits weren't bits, the Internet and all within, including this post, would disappear in an instant. Sorry.
Darth Vader
From the Dark Side
There is a key difference between a CD transport and a bog standard CD drive in a computer. With a transport the digital data stream is in real time and may contain uncorrected errors i.e. distortion. That is why some transports are so expensive as its difficult to get error free CD reads on-the-fly. With computer audio the ripping software can reread many times until there is a confidence that the data is error free. In addition the DAC can with CA clock the data and take full control unlike a CD player that has the transport directly connected to its internal DAC. This can result in greatly improved sound quality using a computer/DAC.
Cheers,
DV
Whaleblue
Southbound
DV, my understanding is that (all?) CD players use a buffer between the transport and DAC. Granted, in "real time" a player only has so much time before the buffer runs out, but in practise that rarely happens.
A CD rip of a tricky to read (perhaps damaged) might get around an "unplayable" CD.
A CD rip of a tricky to read (perhaps damaged) might get around an "unplayable" CD.
DevillEars
Dedicated ignorer of fashion
For those who find animated pictures easier to understand than wordy text:
What the CD Player Does - Link
Data is stored on a CD in tracks starting from innermost useable data track and ending at the outermost useable data track. The data is stored in a sequence of etched "pits" and un-etched "non-pits" and the sizes (or length of "pit" and "non-pit") are standardised and defined in the Red Book. In other words, the amount of data stored per linear unit is fixed by the Red Book standard.
In addition to fixing the linear data storage density, the Red Book also fixes the data read rate (at 1x) for audio CD at 174,600 Bytes/sec.
A CD has a diameter of 12cm which implies a radius of 6cm, of which only a part is useable (less outer rim and inner clamp space leaves about 3.5cm of "useable radius". The radius at the innermost useable data track is ~1.5cm and the radius at the outermost useable data track is ~5.5cm.
If we calculate the circumference at these two tracks:
a) Innermost: r =1.5: 2 x 3.142 x 1.5cm = ~9.4cm
b) Outermost: r = 5.5: 2 x 3.142 x 5.5cm = ~34.5cm
The circumference at the outermost useable track is 3.6x the circumference of the innermost useable track - so, given a fixed data density per cm, the amount of data to be read from the outermost track during one revolution is 3.6 x as much the amount of data to be read from the innermost track.
With a fixed data read rate of 174,600 Bytes/sec and with track content varying by as much as 3,6 times (from inner to outer), the spindle motor HAS TO BE CAPABLE OF CONSTANTLY VARYING ITS SPINDLE SPEED BASED ON THE POSITION OF LASER PICKUP.
In this case Spindle Speed in revs/min can be defined as angular velocity (eg in degrees/sec).
Maybe that helps...
Dave
What the CD Player Does - Link
Data is stored on a CD in tracks starting from innermost useable data track and ending at the outermost useable data track. The data is stored in a sequence of etched "pits" and un-etched "non-pits" and the sizes (or length of "pit" and "non-pit") are standardised and defined in the Red Book. In other words, the amount of data stored per linear unit is fixed by the Red Book standard.
In addition to fixing the linear data storage density, the Red Book also fixes the data read rate (at 1x) for audio CD at 174,600 Bytes/sec.
A CD has a diameter of 12cm which implies a radius of 6cm, of which only a part is useable (less outer rim and inner clamp space leaves about 3.5cm of "useable radius". The radius at the innermost useable data track is ~1.5cm and the radius at the outermost useable data track is ~5.5cm.
If we calculate the circumference at these two tracks:
a) Innermost: r =1.5: 2 x 3.142 x 1.5cm = ~9.4cm
b) Outermost: r = 5.5: 2 x 3.142 x 5.5cm = ~34.5cm
The circumference at the outermost useable track is 3.6x the circumference of the innermost useable track - so, given a fixed data density per cm, the amount of data to be read from the outermost track during one revolution is 3.6 x as much the amount of data to be read from the innermost track.
With a fixed data read rate of 174,600 Bytes/sec and with track content varying by as much as 3,6 times (from inner to outer), the spindle motor HAS TO BE CAPABLE OF CONSTANTLY VARYING ITS SPINDLE SPEED BASED ON THE POSITION OF LASER PICKUP.
In this case Spindle Speed in revs/min can be defined as angular velocity (eg in degrees/sec).
Maybe that helps...
Dave
DevillEars
Dedicated ignorer of fashion
I think we have a misunderstanding of the purpose of a buffer as used in audio CD replay.
Its designed purpose (as a FIFO or First In/First Out buffer) is to accept a data element (or frame) into the buffer, provide the disk controller time in which to perform its data integrity checking and, where necessary, to apply any corrections to the content, before allowing that data element (or frame) to be passed on.
Each data element is a frame comprising 12 x 16-bit samples (total = 192 bits) plus the CIRC (error checking) data of another 64 bits plus another 8 bits for sub-codes (to control the read process) to give a frame size of 274 bits.
These buffers are not very large - just enough to handle the error correction in-line. They're certainly not large enough to provide for buffering to counter the 3.6x difference in circumference...
The one exception that I know about was the PS Audio PWT (Perfect Wave Transport) which was labelled as a "memory player" equipped with a buffer of 64MB that would, on disk insertion, first load the buffer (a good few seconds) and only once the buffer was full would it start playing. The demo I saw was built around ejecting the disk and listening to player continuing to play from the buffer... The rationale behind this design was to utilise PS Audio's Digital Lens to allow accurate re-clocking to eliminate jitter...
I hope that helps...
Dave