hmm. Paul Frindle (DSP Expert and Digital Audio Guru had this to say about DACs)
(posted with his permission) I trust his word over most others(well, he and Bruno Putzeys- who was the head of Engineering at Phillips at one time) nothing at all about "noise" There are only 2 things a DAC responds to; 1) the data we feed to it , 2) the timing information it gets. For the data; data is data - there is no possibility that identical data sets could ever produce a different sound, regardless of their origins. In short, numbers are numbers - and if they are the same, they are the same - period. For timing it's a slightly different matter, because it is essentially and analogue signal - it's properties (i.e. rate) are analogue in concept. So there is a slight possibility that interference on the clock signal can affect the DACs performance, if the timing is modulated in some way, by slightly changing the rate of plyout with time. Of course a good DAC system will circumvent this possibility by using it's own internal clock and some buffering of the data - so that the DAC's timing follows the filtered average rate of the input timing - such that short term timing rate variations (due to interference) do not make it through. I.e. it will synchronise to the input clock, rather than simply passing the input clock straight into the DAC.. You can almost think of it as stacking up the data as it ccomes in and playing it out using it's OWN high quality clock set to the same rate. However - as you can imagine, price competition tends to rule out anything that might increase the cost of the product - and so you will have to spend extra money on your DAC system to get this.. So where does the timing modulation of the clock rate come from (sometimes called jitter)? First on the list are wires and connections. Line frequency hum, RF and interference getting into clock cables will modulate the timing at the recieving end. If you DAC doesn't reject them (as above) performance may suffer. Next on the list is bad design. For instance, in consumer players where the DAC is within the player box, power supply modulation from bad design may cause internal circuits to interfere with each other. For instance if the motor servo is being varied by slightly eccentric discs and/or wobbly ones that stress the focus servo, the cyclic changes to current draw my affect the clock oscillator if the power supply is badly desogned etc.. So although the data is correctly read, the DAC itself may perform less well than it might, due to internal design flaws.. And of course this is true of any electronic system... So there you go - it's a simple as that - no PHD required :-) In summary: Data itself coming from different systems cannot cause a change in sound - if the data values are both identical. But hardware may perform slightly differently if the timing integrity is compromised. Having an external DAC does not avoid the issue - unless it's a very good one with internal timing re-clocking. In which case it will be effectively immune from timing errors and will sound the same whatever way it gets connected, providing the data is correct. So instead of worrying about data coming from Macs or PCs and/or a whole load of hot air from HiFi zealots filling pages with 'waffle' - get yourself a high quality DAC and say bye-bye to the whole discussion :-) I hope this helps.. Paul -- TheOctavist Vortexbox>SBT(stock)>>Forssell MDAC-2>>>Klein and Hummell 0300D Sota Sapphire/Lyra Kleos>>Bespoke Valve Phono Stage>>Mastersound Due Venti>>Link Audio K100 ------------------------------------------------------------------------ TheOctavist's Profile: http://forums.slimdevices.com/member.php?userid=52700 View this thread: http://forums.slimdevices.com/showthread.php?t=94352 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
