Uwe Beis adc project

[Klaus Mogensen]

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.

 

[living sounds]

Hi Klaus,

how does the ADC sound? I'm thinking about building one, but it would only make sense to me it if were a significant improvement over - say - latest generation RME quality. I don't care for S/N as much (anything above 105-110 db should surely be good enough) as for things like transparency, transients, overall pleasantness/"warmth" etc.

Thanks alot!

Gregor

 

[NewYorkDave]

Thanks for the link.
Be sure to check out Uwe's main electronics page while you're there. Very cool... lots of original designs.

 

[Klaus Mogensen]

Hi Gregor

I have compared it with M-audio firewire 400 and RME fireface 400, but I only have Fostex PM0.5 monitors and some old homebuilt discospeakers with Peerles units. So it is a bit difficult for me to tell the difference between the RME and the diy adc. I tried to measure THD + noise and couldn't see much difference between RME and the diy adc, while m-audio had some more noise.
In principle the jitter should be lower, because the clock I use is specified to around 3 ps, while RME write < 1 ns in the manual, but this may not translate into 'improved pleasantness'. For the diy adc you have the opportunity to play around with the analog components, which probably affect the sound most.

I don't know if this helps. Good luck.

 

[living sounds]

Klaus,

what clock do you use? I wonder if it is worth to buy a clock like this:

http://www.tentlabs.com/Products/cdupgrade/xo2xo3/index.html



Gregor

 

[Moby]

Guys, what happened with this? Did somebody contacted Mr Beis about kit?

 

[Davo]

I built a beis adc a while back and use it all the time..... it absolutely smokes the adc on my digi002 (even if that's not saying much)
So if you want to DIY an ADC, this is a pretty good deal.... and Uwe is a great guy to boot!

dave

 

[digichild]

so how much were all the parts?

 

[Davo]

I think it was around $200 USD including an upgrade of the chips etc.  not including the case....
I checked his site though and it reads:

"Sorry, this kit is currently sold out and I don't
know whether or when it will be available again."

So you may want to contact him to find out if it's even available.

dave

 

[Moby]

I contacted mr Uwe and yes, ADC and DAC kits are not available right now. Actually, he doesn't know when it's gonna be available again, so I asked him is he interested for organizing a group buy from here. What you think about that?

 

[jdbakker]

FWIW, I must note that while his design is quite nice, the clock synthesizer he uses introduces quite a bit of jitter (the price you pay for getting support for so many different sampling rates in one small part).

JDB.

 

[Moby]

Yes, 190ps seems to be high. Is it possible to replace it with something better?

 

[jdbakker]

Yes, 190ps seems to be high. Is it possible to replace it with something better?

Probably, yes, if you don't mind sticking to one sampling frequency only.

On further inspection, I'm a bit less happy with the design than I originally was. Most notably:

- rather meagre decoupling for the analog subsystems on both boards, especially the DAC board.
- DAC MCLK supplied by the PLL in the SPDIF receiver and routed through a CPLD, which doesn't help jitter much.

I would expect distortion and noise performance to be less than ideal, albeit probably not by very much. And if you already have one and like it, more power to you.

JDB.

 

[Moby]

No I don't have it. I just found it as only available ADC DAC diy kit. Acually I don't have an idea how it sounds. I own Lynx and RME adi8pro interfaces. Do you know some other project kit available?

 

[jdbakker]

Do you know some other project kit available?

Good question. I believe forum member mcs has/had one, but that might be ADC/DAC only. I'll have a search.

JDB.
[and as has been pointed out before, you could do a lot worse than get manufacturers' eval boards]

 

[Moby]

Yes I know MCS  ;D I didn't know that he started a kit 

 

[Moby]

I started a feeler about AD24QS  ;D
http://www.groupdiy.com/index.php?topic=30752.msg372682#msg372682
let's see :

 

[Moby]

I updated the feeler with new sound samples. New Beis competitor is Lavry blue. Hmmm, interesting ;D