Bit perfect?

[admin_exported]

I understand that one of the problems with CD players is that the resulting signal is not bit perfect, unsurprising when you give some thought to the technology (laser reflecting off minute markings on a rapidly spinning plastic disc).

But what about hard drives? They also involve rapidly moving disks (except for solid state obviously). Are they immune to errors in reading?

 

[Craig M.]

i'm sure someone will answer about the hdd soon but, according to benchmark media, most cd players can output a bit perfect stream.

 

[Anonymous]

I think hard drives will be "bit perfect" if the music files are extracted over a network - i.e. to a Squeezebox or Airport Express - just in the same way as your documents are not waffle when you drag them over your LAN to another computer.

Stereophile magazine measured the Airport Express, which is the cheapest audio accessory going, and concluded that the optical output of the unit was "bit perfect" - i.e. identical to the bits in the original music file.

I don't think a CD player will be far off bit perfect, although it has the disadvantage of reading in real time.

You probably wouldn't hear a missing few bits.

The sound is in the DAC, and something like a DAC Magic is probably all that you need.

There are much bigger gains to be had in the loudspeakers.

 

[Anonymous]

I wouldn't directly agree with the above.

As I am aware these tansmissions are not bit perfect on the fly. If I read a bit (1 bit) of data and send it from A to B, I have no guarantee that the bit will come out correct. (That is true for CDs, DVDs, HDs, BD...).

But all such (modern) transmissions have some kind of error detection and correction algorithms implemented.

i.e.

TCP/IP: Each Ethernet frame carries a CRC-32 checksum. The receiver discards frames if their checksums do not match. And many more...

And so in the end you get bit-perfect information on the other end (but some packets of incoming information were discarded because of error correction). Everything must be fast enough, so an user can think that it is real-time.

 

[Anonymous]

Nejc Trdin: all such (modern) transmissions have some kind of error detection and correction algorithms implemented.
i.e.

TCP/IP: Each Ethernet frame carries a CRC-32 checksum. The receiver discards frames if their checksums do not match. And many more...

And so in the end you get bit-perfect information on the other end (but some packets of incoming information were discarded because of error correction). Everything must be fast enough, so an user can think that it is real-time.

I wondered if that were the case. Would that also be true of a NAS feeding a DAC? If so, how is the error correction handled? (i.e. without a PC in the picture)

 

[Anonymous]

Hard drive doesn't have to work in real time as CD players do.
It keeps reading the data until it is perfect.

Computers wouldn't work otherwise!

What is laid down on the HD is an exact copy of what was put onto it at the bit rate used. It will keep repeating it until it is.

The future is heading in this direction, the Ipod showed the way and better bit rates is following.

 

[Thaiman]

I have been investigate this "bit perfect" ripping/reading now for few weeks and with my high hope of Hard drive will sound as good as a redbook transport, I have been buying, borrowing, lots of listening and days of reading to find out.

The result is not what I was hoping for, it seem that I still have to get off my bum and push that open button to change the silver disc a bit longer yet. Well I suppose unless you are going down highend HD base dedicated system route like Naim (even my Yamaha MX2000 is not bad at all), a proper CD player still win the day. I am not talking miles apart in preformance here though, the most different being instruments texture that normally effect listener's emotion. If you are not using the most revealing pair of speakers like myself though, it might be even closer.

 

[Anonymous]

tractorboy:Nejc Trdin: all such (modern) transmissions have some kind of error detection and correction algorithms implemented.
i.e.

TCP/IP: Each Ethernet frame carries a CRC-32 checksum. The receiver discards frames if their checksums do not match. And many more...

And so in the end you get bit-perfect information on the other end (but some packets of incoming information were discarded because of error correction). Everything must be fast enough, so an user can think that it is real-time.

I wondered if that were the case. Would that also be true of a NAS feeding a DAC? If so, how is the error correction handled? (i.e. without a PC in the picture)

Every (digital) unit in your system has some kind of a CPU installed (CD,DVD,TV,DAC...). In that case you do not need a PC, because basic error correction can be handled by hardware.

The same goes for the PC. i.e. the hard drive has it's own "CPU", which has so called SECDED algorithm (single error correction double error detection). Other PC components have similar algorithms.

Obviously you don't need these algorithms in analog transmissions. That is why we put a lot on cables, so we keep the errors down.

 

[Anonymous]

Got it. Thanks for the detailed reply.