squeezebox set up for audiophiles

dhinesh wrote:
You mentioned '0' and '1' are the same in a digital signal, this opens another can of worms. :D If they are the same why do we get different sound from different digital cables / coaxial / spdif cables.

The Audiophile focus on cables when discussing digital communications is quite amusing. I shall try to explain some of the key reasons:

In digital communications such as ethernet, data is guaranteed to be transmitted "bit accurate". That is because as well as the data, checksums are transmitted with, and based on, the source data. The receiver then recalculates those checksums and if it does not match the checksum that has been received the receiver knows there has been an error.

In that scenario the receiver asks the source to resend the data - it does not proceed and use the erroneous data.

Via this checking and retransmitting on error, perfect data transmission is guaranteed - or if the error persists the erroneous data is discarded and you will hear this in sound equipment as 'skipping' and pausing. I'm sure you have experienced this when trying to stream over the internet - it's the same thing.

This is why it does not matter what the transmission path from NAS to Touch is because the data is guaranteed to be correct or absent. This is also why you will not hear any incremental improvement in sound quality by playing around with the NAS, ethernet cables or your networking equipment. If there is a problem in that area the audio result is very obvious - with the worst equipment and poorest hearing it will be noticable.

(Note: There are other aspects I haven't covered such as flow control, what to do if data is not received at all etc, but hopefully you get a sense of how digital systems are designed to always deliver data accurately)

This technique however relies on the ability of the receiver to request data to be resent. Unfortunately in audio peripherals such as DACs, this technique is not used. There is no reason it couldn't be, but it is perhaps more costly and certainly more complicated due to the requirement to configure the network link.

Audio equipment comes with the history of just being able to plug things together without needing to configure anything, and the move into digital domain reflects this with the introduction of the likes of SPDIF and more recently asynchronous USB.

To make these connections "simple", like their analogue forebears, retransmission of erroneous data is not supported. Instead techniques such as error correction are used such that the receiver can detect and automatically correct errors. It is still possible to get errors, but these *should* be corrected. Even if not, the audio consequence will be very dependant on the receiver. The data could be dropped, so introducing "skipping", or the receiver could interpolate (ie guess) what the data would have been, or just uses the erroneous data. But given the randomness of errors if either of the last 2 options are used, these would be very unlikely to impact a particular frequency band or aspect of the audio but rather would be different every time you listen.

For these implementations - if properly engineered & setup they just work and doing things like adding attentuators or using "high quality" expensive cables will make no difference, possibly quite the opposite as you saw when one of your changes resulted in no audio at all.

Or why would a meicord ethernet or a denon ethernet cable matter if '0' and '1' stayed the same?

Exactly - why bother with such expensive cables? (I hope you have realised by now that my inital post was not serious, but not as funny as the "Spreadsheet" post on the identical thread you started over on the logitech forum: http://forums.slimdevices.com/showthrea ... 419&page=5)

Provided the cable used meets the prescribed specification, a $5 cable will perform no worse than a $500 cable and anyone who claims differently is quite honestly full o' $hit

Here's a link to that denon cable on amazon - now selling for $10,000 - read the comments, if only for humour...

http://www.amazon.com/Denon-AKDL1-Dedic ... 976&sr=8-1