Elektor DAC 2000

[johnny1]

Well...
A common question again...
Does anyone of you has ever tried this DAC? For the guys that do not know what I am talking about, it is a DAC based on the CS8414/ DF1704/ PCM1704 combination.

[peranders]

I have seen it and I must say it ti very well done with OPA627 (really expensive) in the output filters and also very nice loooikng pcb's with split groundplanes see Cheap 24/96 DAC with CS43122

The DAC chip PCM1704 is one of the best, the measured performance is excellent.

I have never listen to it but I have a hunch of it may be rather good.

BTW: IC10, IC12 looks weird, is the schematics right? The minus input is shorted with the output of the opamp? Can anybody explain the output filter for me?

[promitheus]

Hello,

I am still building this DAC but I am not finished.
The reason I started it was because it has one of the best chip sets around. The PCBoards are also very good designed with ground plane and everything. It really is worth buying them ready made. I got them from a company that makes Elektor pcbs and that are high quality.

I will use it with the Upsampler board that was published later from Elektor magazine so I don´t have to build the input board from the DAC 2000.

Also I want to use a different Analog stage instead of the op amps but I still haven´t found anything.

If you decide to make this DAC also and you live in Europe I can tell you where I got my parts.

[johnny1]

Promitheus...
Thanks for the reply. As far as the analog stage try http://www.borbelyaudio.com/index100.htm
They have some fet designs that look promising.

I already have all the parts and i will have the pcb in the next few days

I will post photos....

[sikkek]

Peranders,

The opamps with ouput shorted to negative input are simply buffers: the output is equal to the positive input. In a formula:

Uo = A*(Up - Um)

Uo = output voltage,
A = Open Loop Amplification
Up = voltage at + input
Um = volatge at - input

Here Um = Uo so

Uo = A*(Up - Uo)

=> Uo = A*Up - A*Uo

=> Uo + A*Uo = A*Up

=> Uo * (1+A) = A *Up

=> Uo = A*Up / (1 + A) = Up * A / (1 + A)

Because A is very lage (> 100.000), the term A / (1+A) basically equals 1, so

Uo = Up

(With an A of 100.000, Uo = 0,99999 * Up )

[Edwin Dorre]

Originally posted by promitheus


If you decide to make this DAC also and you live in Europe I can tell you where I got my parts.

Hi I live in the Netherlands and I am still looking for a good DAC design. Everybody seems to fight about one, talk about one, but I can not find good ones. Only ones with out-dated chips which are hard or cannot find...

Can you please make scans of the DAC article and the upsampler article of the magazine and email them to me???

My email: edwind@xs4all.nl

Thank you very very much in advance,

Edwin

[guido]

Edwin,

Try DIL (www.dil.nl), you can get the whole DAC 2000 in parts without the powersupply (Euro 451). They have many Elektor projects (elektor/Elektuur is dutch, like DIL, yourself and me..).

If the thing is worth 451 euro, i don't know. Not too fond of elektor:

Groundpins is always an issue. I can remember elektors first dac with the PCM63. Resistor between agnd and dgnd of the DAC.
The databook however says to connect both pins together and then return them to agnd. So why elektor thought they knew better ???

Have an article from Analog devices where they explained why both agnd and dgnd should be returned to agnd (for DACs and ADCs if i remember correctly). Guess this is always the way to do it, unless the datasheet of the dac says otherwise. In the case of the old DAC of elektor, it did not..

The name agnd and dgnd of the dac pins is what they are internally connected to, not to what they should be connected to on the outside.

See what the reactions will be on the above, guess there will be some :->

Groetjes,

Guido (and no not G.Tent)

[peranders]

sikkek, I'm quite aware of the basics but sometimes I can get short circuit in my brain, if yoiu know what I mean?. If I rewrite the schematics I clearly see what's all about. It's a simple 3rd order active filter, rather classic too, hard to see at first.

[sikkek]

Peranders,

Sorry to insult your level of electronic knowledge... I was just trying to help, so don't bite my head off!

[Edwin Dorre]

Originally posted by guido
Edwin,

Try DIL (www.dil.nl), you can get the whole DAC 2000 in parts without the powersupply (Euro 451). They have many Elektor projects (elektor/Elektuur is dutch, like DIL, yourself and me..).

If the thing is worth 451 euro, i don't know. Not too fond of elektor:

Thanks,

I am looking at all opions. However I think DAC design for DIY are rather hard to find, at least good ones. As I stated earlier, most use outdated chip-sets.

My father sometimes build thinks from elektor and it did not alway work the first time (you needed 'Het Lek' to get it working!) . So that's why I wanted to see the design before looking for the parts!

Do you know a good DIY dac design?

Edwin