Le jitter

Citation : la différence qualitative entre un converto moyenne gamme (type RME) et un converto high end (type lavry ou prism ou autre) est elle "proportionnelle" à la différence de prix, car j'imagine qu'il y a déjà une grosse différence au niveau des coûts de la R&D, le cahier des charges étant certainement plus drastique pour du high end et de plus ce type de produit doit être fabriqué en plus petite série que les rme ou équivalents qui se vendent "comme des petits pains"

Hors sujet : Pour ceux qui veulent quelques détails supplémentaire, voici deux extraits du user guide du Lavry Gold DA924 :

Citation : The PCM DAC is constructed of custom made laser trimmed thin film resistor networks; yet any resistor is subject to short term drift due to temperature variations and long term drift due to component aging. The resistor networks are kept at a constant temperature by a linearly controlled heating element. (A bang-bang controller, such as a home thermostat is undesirable because it produces turn on and turn off surges-- thus audible kicks.) Keeping the resistors at constant temperature overcomes resistor dependency on environmental temperature variations.

Citation : A sequence where each resistor is tapped (one at a time) for voltage comparison against a reference level tells the processor the required adjustments. The voltage difference between any given network node and the reference is greatly amplified and then fed to a strobing comparator (see multiplexers for calibration and error amplifier and comparator gain blocks in the simplified diagram). The processor strobes the comparator and reads its output. The strobing is repeated 4000 times for the sake of averaging out any error due to amplifier noise. At the end of a comparator strobing cycle, the processor decides whether to increase or decrease the specific voltage of the measured node. This is done via the calibration 14 bit DACs (see diagram). Each calibration DAC is used as a 13 bit device to ensure monotonic performance. Each DAC is fed to its corresponding node through a large value resistor, thus a full 10V swing on the calibration DAC can only pull a given node by +/-4mV, providing an effective adjustment of a part in 5 million per calibration DAC step.
The calibration process takes a long time because the node adjustment is interactive (adjusting a node causes some misadjustment at all the other nodes). A single calibration cycle consists of reading and adjusting of all the nodes. The processor repeats the calibration cycle numerous times until all the nodes are set properly. Though nodes interaction exist during the adjustment process, the overall network is guaranteed to converge on a solution by design. Calibrating a DA924 for the first time (at the factory) often exceeds 25 minutes. Once calibrated, the settings are stored in non volatile ram for future startup point of reference, thus all future adjustments are initialized to the last settings. Therefore the initial tolerance of the components is pre calibrated already, and each new calibration needs to deal only with component drift under the same given temperature conditions (ovenized components). The remaining calibration at each subsequent power on takes less then 2 minutes typically.

Citation : En fait, pour parler plus généralement (voitures, montres, convertisseurs, micros, guitares, etc...) plus on monte en gamme, plus les améliorations vont coûter cher.

Citation : Le critère de sélection d'un câble ne doit donc pas être la "réduction" du jitter ou l'absence de jitter puisque c'est intrinsèquement impossible : un câble induit toujours du jitter. Par contre, il existe des différences audibles entre câbles plus ou moins bon. (Ce n'est pas que de la masturbation pour audiophiles, ça existe !)