Klaus Mogensen
Active member
while searching the web I was very happy to find this ADC link a couple of weeks ago.
http://www.beis.de/Elektronik/ADDA2496/AD2496.html
This might also be of interest for some of you since there has been a lot of talk about ADC's without many people actually building them.
I mailed Uwe and he is an very nice guy. I have however reserved the last board of batch no. 2, but he wrote:
".. ask them and maybe there are enough of them so that I can order another lot of boards and probably the other components difficult to get, too."
So, if enough people are interested, then maybe there can be a new batch. It would also make it easier to get the chips, with a group effort, because buying single digital chips is kind of tough.
So why build an adc? My motivation is the same as at http://www.diyaudio.com building DAC's for their cd-player.
a) Upgrade the analog part, and try different layouts
b) Try using a fixed clock frequency (from e.g. http://www.lcaudio.com/index.php?page=4) instead of a PLL (phased locked loop) as in the commercial converters. This should improve the jitter performance (in theory). The disadvantage is however, that selection of sampling frequency cannot be done, which is why commercial converters use a PLL and sacrifice a bit of performance for flexibility.
c) Try different output transformers (Lundahl ll1572 ?)
Overall, I think it is possible to build converters as good or even better than the best commercial ones.
http://www.beis.de/Elektronik/ADDA2496/AD2496.html
This might also be of interest for some of you since there has been a lot of talk about ADC's without many people actually building them.
I mailed Uwe and he is an very nice guy. I have however reserved the last board of batch no. 2, but he wrote:
".. ask them and maybe there are enough of them so that I can order another lot of boards and probably the other components difficult to get, too."
So, if enough people are interested, then maybe there can be a new batch. It would also make it easier to get the chips, with a group effort, because buying single digital chips is kind of tough.
So why build an adc? My motivation is the same as at http://www.diyaudio.com building DAC's for their cd-player.
a) Upgrade the analog part, and try different layouts
b) Try using a fixed clock frequency (from e.g. http://www.lcaudio.com/index.php?page=4) instead of a PLL (phased locked loop) as in the commercial converters. This should improve the jitter performance (in theory). The disadvantage is however, that selection of sampling frequency cannot be done, which is why commercial converters use a PLL and sacrifice a bit of performance for flexibility.
c) Try different output transformers (Lundahl ll1572 ?)
Overall, I think it is possible to build converters as good or even better than the best commercial ones.