TDA1543 PCB Layout

Hello,

I just created a PCB layout for a TDA1543 based DAC (4x parallel) holding all necessary parts on one PCB.

The PCB does not include a SPDIF receiver since I grab the I2S signals directly from the cdrom drive.

I would kindly ask you guys for a review.
Of course I can post all the Eagle files too.

Schematic:
[IMGHTTPDEAD]http://img256.echo.cx/img256/4496/clipboard045lp.th.jpg[/IMGHTTPDEAD]

PCB:
[IMGHTTPDEAD]http://img300.echo.cx/img300/1264/clipboard027gf.th.jpg[/IMGHTTPDEAD]

So what do you think ... any major flaws in the PCB and/or schematic?

Many thanks in advance,
Serge
 
Hello again,

I just wanted to report that I successfully built the DAC and he's playing nice. It was definitely worth the effort.

Here is how I modified the Sony chip:
[IMGHTTPDEAD]http://img231.imageshack.us/img231/7065/small0019ji.th.jpg[/IMGHTTPDEAD]

As you can see it's a CXD2529Q where the pins 50, 52 and 54 are of interest. If you have this sort of sony chip take care to buy a TDA1543A.

Now here is a picture of the PCB. As you can see my electronic supplier didn't have the 680pF in stock (I wanted FKP) so they are not placed yet:
[IMGHTTPDEAD]http://img231.imageshack.us/img231/3339/small0033kq.th.jpg[/IMGHTTPDEAD]

I'm not too happy about the placement of the MOSFET. It still is not optimal for heat sink mounting and it gets VERY hot. This heat sink on the picture is way too small.

Another option todo on the pcb is to modify the Vref resistor (330 Ohm) to a pot. With the 330 Ohm in place I had to increase the voltage nearly up to 9V in order to get a clean signal. After lowering to 220 Ohm I got a clean signal at 5V.

Do you guys have an advice regarding Vref for the TDA1543? Unfortunately I do not have a scope (actually I'm a newby in electronics) to check which resistor value is optimal for 5V with 4 chips in parallel.

I have also another question regarding the audio output. After lowering to 5V the audio signal was very silent comparing to driving the chips at 9V. What sort of output circuit do I need? When I'll built a buffer the signal won't be louder, right? I need some sort of amplification?

Greetings,
Serge
 
Another option todo on the pcb is to modify the Vref resistor (330 Ohm) to a pot. With the 330 Ohm in place I had to increase the voltage nearly up to 9V in order to get a clean signal. After lowering to 220 Ohm I got a clean signal at 5V.

Do you guys have an advice regarding Vref for the TDA1543? Unfortunately I do not have a scope (actually I'm a newby in electronics) to check which resistor value is optimal for 5V with 4 chips in parallel.

I have also another question regarding the audio output. After lowering to 5V the audio signal was very silent comparing to driving the chips at 9V. What sort of output circuit do I need? When I'll built a buffer the signal won't be louder, right? I need some sort of amplification?

Greetings,
Serge [/B]

The value of the I/V resistor and the Vref resistor must be chosen in order to let the DAC work properly.
Basically you want to maximize the output swing without making the output pins get out of the linear region (Vcc-1.2V ---- 1,8V IIRC). To do so you have to choose the appropriate I/V resistors and then trim Vref to set the idle voltage in the middle of this region.

To do so you can look at the datasheet or take a loot at www.dddac.de where this is all explained.

Cheers

Andrea
 
Hello Andrea,

Thanks for the answer! Actually I should have looked this up myself :apathic:

After a few hours listening to this DAC I have to say that it is really nice, it improved my cheap sony player a lot :) So I think I'll leave this "high-voltage" setup with 8.5V and will apply better heat sinks to the chips and the voltage regulator mosfet.

Thanks to the maintainer of the http://www.jogis-roehrenbude.de/Leserbriefe/CD-Player-Projekt/CD.htm and the TNT convertus site who made the circuit freely available !!

BTW, I have also found a cathode follower circuit on the net using a 6922 tube which I would like to apply after the DAC as a buffer. Do you think this would make sense? I already played a bit in Eagle to make a PCB and it is nearly finished. Any interest for the PCB? when I'll be ready I can publish it again.

Bye and sorry for my newbish questions, but I'm no electrician, just doing this as a hobby ;-)
 
If you want to go with tubes you might consider a tube output stage, if I recall correctly there was a version with E88cc (=6922) by Thorsten for the TDA1543.

Sincerely don't know if the added complexity will be paid back by a similar change in sound :cannotbe:

In any case it can be a useful experiment.

Can you post the cathode follower schematic you are referring to?

Cheers

Andrea
 
I think I will try that anyways. I have a spare 6922 flying around so why not. The other parts don't seem to be too expensive.

I found the circuit on a Tawinaneese web page which unfortunately is not online anymore so here are the schematics which I have as a backup on my disc:

[IMGHTTPDEAD]http://img58.imageshack.us/img58/9211/modifiedtubebuffer7oj.gif[/IMGHTTPDEAD]

And here the PSU part:

[IMGHTTPDEAD]http://img134.imageshack.us/img134/5098/taiwanpsu6rz.gif[/IMGHTTPDEAD]

What I like about the circuit is that it doesn't need fancy Kilovolt transformers which I'm still a bit afraid of when I think of tubes ;)

Attached is also my Eagle files for the audio part. The PSU part is on my TODO list.
 

Attachments

  • tube buffer.zip
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