Bonjour,
A propos du convertisseur AK4396, voici un interessant message vu sur le yahoogroup DCX2496 :
Citation :The AK4396 has been around for a couple of years now and I have had a
lot of people asking me about it as a possible upgrade to the AK4393
that comes stock in the Behringer 2496 audio gear but I have just now
been able to get my US distributor to supply them. I installed an AK4396
dac chip in a direct out modified DEQ in order to compare it with the
AK4395 that I have been recommending. The 4396 drops in to the board
space vacated by the AK4393 and works fine on 3.3v with no other mods
whereas the 4395 needs an extra regulator to provide 5v to pin 2,
assuming that you don't want to share the analog 5v with the digital
pin. It's interesting that the two chips do sound quite different.
Although I usually have little trouble picking one component I like best
from listening trials, it has been very difficult for me to choose a
clear winner this time. These chips both offer stratospheric
performance. It's funny that I actually started to feel some
pressure from my indecision. I also swapped the boards into the opposite
chassis to make sure that I was minimizing the variables and tried both
4k and 20k stepped attenuators even though the 20k attenuators don't
work as well with my 22k amps. The 4396 has a more powerful sound even
working into my 4k stepped attenuators despite it's lower stated
power consumption. It throws it's soundstage closer to the listener,
more toward the front line of the speakers and actually plays about 1db
louder depending on the program material. The 4395's bass was heard
to extend much further than the stock 4393's, along with a big
improvement in resolving ability, and the 4396 has just as much
extension, with a higher level, up into the mid bass. This makes the
4395 sound a bit lean in comparison. On the other hand, the 4395 throws
it's sound stage much deeper, starting just behind the plane of the
speakers and going back beyond the front wall of the room. The
4396's stage is pleasantly a bit taller. The 96 lights the stage
more brightly, making each instrument stand apart from the others but
lacks the ultimate resolution of the 95's ability to follow the
sounds right to the fine end. Some tracks favor the 4396's closer
presentation as feeling more involving and easier to follow. On other
cuts I preferred the 4395's extra ability to resolve reverberation
tails and ambient information, making the 96 feel like it is leaving
something behind. So the trade offs went back and forth causing one of
those listening binges where you just keep pulling one cd after another
off of the shelf, and can't wait to get home the next day to do it
all over again. At this point, with my current associated equipment, I
will have to choose the AK4395 for it's extra resolving ability even
though I was hoping the 4396's more focused and powerful sound would
win as it would be easier to install. With different equipment I can see
where this might go the other way so I will check back on the 4396 as
things in my system change.
Il resort que le AK4396, s'il est le dernier sorti de la gamme, n'est pas forcement le meilleur...
Citation :Je suis assez surpris de voir que de nombreux constructeurs proposent des préamplis ligne complexes, avec de très nombreux composants. Qui à raison?
Difficile de faire des généralités...
Mais si l'on considère par exemple un étage ligne avec un simple common cathode + cathode follower chargés par resistances, une version chargée avec deux sources de courant sera supérieure en terme de distortion et de bruit, et offira donc une meilleure transparence (toute chose égale par ailleurs). Une
bonne alim régulée sera aussi supérieure en terme de bruit de fond à une simple alim diode+filtrage RC.
Bien sûr, il existe des schéma complexes déplorables, et des schémas simples excellents.
Mais j'ai la conviction que, pour un préampli à tubes, les meilleurs résulats passent par des charges actives et une alim active, à condition bien sûr que ces circuits soient parfaitement maîtrisés.
S'il fallait dépenser plusieurs milliers d'euros pour un preampli du commerce, j'irai donc plutôt voir chez audio-research, mais c'est juste une opinion personnelle.
Jérôme