Aylwin wrote: > I would be willing to accept Mike's -"good enough"- but I have trouble > with -"it's only a matter of having no errors"-. However, I think one > key point from the definition above is, -"The amount of allowable > jitter depends greatly on the application"-.
I agree, and possibly the confusion arises because there are two distinct applications in place when using an SB2. I think the issue here is more the management or errors. Protocols like TCP/IP (which are used for PC <-> SB2) have inbuilt checks to identify errors (caused by jitter). In this case they can simply be requested again and corrected. This means the SB2 is always processing from a perfect copy of the wav/flac/mp3 sent by the PC. For PC networks errors are a normal part of operation, but no-one notices because the built in protocols correct the errors before any downstream processing happens. In a pure audio stream (such as you get from a CD transport) there is no error correction or buffering so if jitter causes an error there is no way to identify it unless it causes a nasty spike and no time to request a resend to perfectly correct it. In this case interpolation has to be used and this degrades audio quality. So in summary, the digital (network) link between the PC and SB2 and the digital link from SB2 to DAC both suffer from jitter, however in the PC/SB2 link the network speed and protocols allow errors to be identified and corrected. The approach taken for identifying and correcting errors in the SB2/DAC stream means that errors reduce audio quality. As regards clock synching and so forth my old ARCAM transport had a separate clock signal, I wonder if this is something that could be considered for the SB3? Actually it might even be possible for the SB2 if the firmware would allow the 2 digital outputs to be used for different purposes (data and clock). Malcolm > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Aylwin > Sent: 08 June 2005 08:09 > To: [email protected] > Subject: [SlimDevices: Audiophiles] Re: "SB2" and "Audiophile" go > together? > > > > seanadams Wrote: > > Agreed - once it's in digital land, it's only a matter of having no > > errors (jitter doesn't count BTW; that's really an analog > phenomenon).Ummm... sorry, I beg to disagree. Jitter is *very* > digital. Okay, > maybe we could argue that it's analog but the point is that it > primarily affects the digital domain. Being lazy, here's a definition I > found on the internet: > > -Jitter is the deviation in or displacement of some aspect of the > pulses in a high-frequency digital signal. As the name suggests, jitter > can be thought of as shaky pulses. The deviation can be in terms of > amplitude, phase timing, or the width of the signal pulse. Another > definition is that it is "the period frequency displacement of the > signal from its ideal location." Among the causes of jitter are > electromagnetic interference (EMI) and crosstalk with other signals. > Jitter can cause a display monitor to flicker; affect the ability of > the processor in a personal computer to perform as intended; introduce > clicks or other undesired effects in audio signals, and loss of > transmitted data between network devices. The amount of allowable > jitter depends greatly on the application.- > > I would be willing to accept Mike's -"good enough"- but I have trouble > with -"it's only a matter of having no errors"-. However, I think one > key point from the definition above is, -"The amount of allowable > jitter depends greatly on the application"-. > > I come from the telecoms world where jitter can be a real headache in > digital transmission networks. It probably is less of a factor for > audiophile applications but how much less I honestly don't know. > Still, for a real-time application where digital transmission is > involved I would assume that synchronization and clock recovery are > also important. Please correct me if this assumption is wrong. > > > -- > Aylwin > _______________________________________________ > audiophiles mailing list > [email protected] > http://lists.slimdevices.com/lists/listinfo/audiophiles > > > -- > No virus found in this incoming message. > Checked by AVG Anti-Virus. > Version: 7.0.323 / Virus Database: 267.6.4 - Release Date: 06/06/2005 > > _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
