Stuck as a Duck on the Doede Dac!

[Lucas_G]

There is maybe one thing I should mention:

I have ordered BG caps, but since delivery takes some time, I used som cheap quality 20uF standard (or worse) quality caps. Could they be too bad to prevent oscillating? Or am I already too much influenced by the Blackgate-Mob?

Lucas

[Jax]

I don't like the grounding on this board.

The return path for the 3 digital signals to the 1543 goes all the way to the battery and back to the board again. This is bad design, it may work but will depend on how the ground connections are routed.

I would try to remove GNDA1 and GNDA2 and only use GNDD from the power supply.

Connect a short wire between pins 18 and 21 on the 8412. This is the single point connecting GNDD and GNDA1 together.

Connect a wire from the 1543 pin 4 to the jumper with GNDD on it going to the XO and 4040.

It's easy fixes and can be undone. Give it a try.

Other things to consider is adding 100n ceramic SMD capacitors on the 8412, one between pins 7 and 8 and one between pins 16 and 17. The 20u is not a capacitor at high frequencies, BG or not.

[guido]

Are you sure you are using TDA1543 and not TDA1543A?
Just a thought.

If the DAC's are stone cold when you power up the dac and it goes wrong right away, it can't be overheating i guess.

Replace the DACs with just one and see what happens.

GuidoB

[Fabian]

Lucas,

I've also built Doede's dddac. In the beginning all I could hear was a lot of noise but almost no music. Quite similar to your description. It took me more than a day to find the problem: LT1085 just didn't work (although it measured well). After replacing with a LM317T it worked fine.

BTW: Doede recommends 3.85V, not 3.5V as you mentioned in post #6

Fabian

[Jax]

LT1085 needs at least 150uF on the output if a bypass capacitor is used on the adjust pin. A 10uF is also needed on the input pin to ground since the distance to the source is significant. Else it may oscillate.

LM317 is more stable but noisier and need no capacitor at all on the output.

[jewilson]

You should be using a buffer somthing like a 74ACT244 to drive all those DACs. That's to much of a load on the 8412.

Also, check to make sure you have set modes M0,M1,M2, M3 correctly. The can change with different DACs.

Also, change filter cap on the 8412 to a .047uf film cap, don't use an electrolytic there.

[finneybear]

Lucas, if the problem existed already when the DACs were cool, then I am running out of clue as well. Probably you just have to try the simple but dumb way... replace the parts one by one to see how it goes.

The Doede board looks good to me already. Yet if I have to make a new board myself, definitely I will add more buffers to the 8412 and reroute the ground.

The 4x2 idea goes this way: A is for the top, B for the bottom. The arrangement looks like: ABAB. This will ensure any two adjacent sets will always share one side to have the shortest signal path. Now I will have to come out a good way to connect the right signals together. Probably through p2p shielded silver wires? Another good thing about this topolgy is that there will be no signals go between the pins. I can put ground lines around them instead.
It will be easy to install heat sinks as well. Probably no need for a fan anymore.

[Elso Kwak]

Originally posted by Lucas_G
Dear Dac builders,

I had completed the Doede TDA 1543 DAC a while ago.

http://www.dddac.de/ma_dac21.htm

However, It does not what it is supposed to do.

It is quiet when no digital SPDIFF signal comes in, but as soon as I feed it with some digital data, it starts making a high frequency noise, in which you can faintly hear some parts of the music in the background. The louder the digital signal, the louder the fuzzy noise...

I have tried everything I could in the past week.
I also asked Doede some questions, but he prefers not to go into detail - which is his good right, of course. He never promised anybody to give support on his design....

Now, I am very much hoping that someone else can give advice.

All measurements with my multimeter seem to be ok.
I get 5.04 Volts on VBD and VBA1.
With VBAdjust on 1.25 kOhm I get 7.5 Volt at VBA2.

Here is the scheme:
http://www.dddac.de/pics/dddac1543/pcb1543.gif

I have two questions:

1. In some older schemes, Doede mentions 10 nF caps at the SPDIFF In and Ground. On later schemes he uses 100 nF caps (so that is what I used). Could it be that the use of 100 nf instead of 10 nF is responsible for the fuzz?

2. I did solder all the chips straight in the pcb (except for the Tent clock). I used a 20 Watt soldering iron, and I worked quickly... Is the CS8412 extremely sensitive to heat?

Any suggestions extremely appreciated!!!!

Regards,

Lucas

Hi Lucas,
Just a short advice if not already done:
Check all supply voltages.
Check with a scope if BCK, WS, and DATA are present at outputs on the CS8412 when playing a CD.
If you have a lock light see or measure if the CS8412 is locked to the datastream. Check very carefully if you have the right mode for the CS8412. TDA1543 needs mode#2 I2S outputformat. (table 3 in the datasheet)
Also check as already suggested if the DAC works without the "reclocking" The latter requires also special setting of the CS8412. Again see the datasheet.
Hope this helps.

[Lucas_G]

Originally posted by Jax
I don't like the grounding on this board.

The return path for the 3 digital signals to the 1543 goes all the way to the battery and back to the board again. This is bad design, it may work but will depend on how the ground connections are routed.

I would try to remove GNDA1 and GNDA2 and only use GNDD from the power supply.

Connect a short wire between pins 18 and 21 on the 8412. This is the single point connecting GNDD and GNDA1 together.

Connect a wire from the 1543 pin 4 to the jumper with GNDD on it going to the XO and 4040.

It's easy fixes and can be undone. Give it a try.

Other things to consider is adding 100n ceramic SMD capacitors on the 8412, one between pins 7 and 8 and one between pins 16 and 17. The 20u is not a capacitor at high frequencies, BG or not.

Hi Jax,

I see your point regarding grounding.
Doede wanted to remain all options open for using several powersupplies...

But I will try your suggested fix.

I have only 100nF polyester at hand. Is a ceramic obligatory?

Regards,

Lucas

[Lucas_G]

Originally posted by guido
Are you sure you are using TDA1543 and not TDA1543A?
Just a thought.

If the DAC's are stone cold when you power up the dac and it goes wrong right away, it can't be overheating i guess.

Replace the DACs with just one and see what happens.

GuidoB

Hi Guido,

It is the TDA1543N (ordered from Reichelt).

It is bit difficult to replace the DAC-tower with just one; I made a stable tower with the help of heat-paste-glue...!

But I may have to maltreat the board anyway...

Regards,

Lucas