Simple, good quality DAC

[rbroer]

TDA1549 internal opamp bypassed:

just to make it more clear

[miguel2]

Got the TDA1543 working. For the I2S I used two direct solderings to pcb's wires (jumpers) and one short (5cm) coaxial wire. Outputs and Vref have 1K metal oxide 0.5W resistors. 47k resistors to ground. And 4.7 uF regular electrolytics. In the psu wires I put a 22 uF and a 1 uF caps.

I just dont know where to get a decent 5V supply indide the player. For now I connected it to the uoput pin of the 7805 chip and the ground is directly to the case. But this is not a good solution...

The sound level is a bit low, even with the maximum level on the cdp (yes the volume control still works ). I tried to use my EF86 based pre but it didnt solve it (has not enough gain). As I use a opa549 gainclone, maybe I increase the feedback resistor to get more gain.

Miguel

[Elso Kwak]

Originally posted by miguel2

The sound level is a bit low, even with the maximum level on the cdp (yes the volume control still works ). I tried to use my EF86 based pre but it didnt solve it (has not enough gain). As I use a opa549 gainclone, maybe I increase the feedback resistor to get more gain.

Miguel

Hi Miguel,
Also my experience: output is pretty soft, low with 1k resistors and passive conversion.
With 3k65 as Rconv as in Rudolfs schematic and a OPA604 opamp I got a lot more power and output.
(10 clicks on my volumecontrol or about 15 dB)

[miguel2]

I have a couple of OPA134s that I can use there, in a typical configuration used by TI in the dacs sheets.

Miguel

[Elso Kwak]

Originally posted by miguel2
I have a couple of OPA134s that I can use there, in a typical configuration used by TI in the dacs sheets.

Miguel

Hi Miguel,
OPA134 also works. I tried OPA2134. OPA604 has slightly more refined sound.

[miguel2]

Hi Elso,

Can you point me a schematic of the Rudolfs dac? Yesterday I tried the OPA134s and could not get it working. The TDA1543 alone works well. And my implementation of the OPA134s seemed to work well too, with inverted input and unity gain (for starting). But when I connect the output cap of the TDA1543 to the input resistors of the opamp the sound becomes very degradated and with a lot of hum. I tested both the outputs of the dac and the opamp. I believe that I grounded well everything, so there must be other problem...

Miguel

[Elso Kwak]

Originally posted by miguel2
Hi Elso,

Can you point me a schematic of the Rudolfs dac? Yesterday I tried the OPA134s and could not get it working. The TDA1543 alone works well. And my implementation of the OPA134s seemed to work well too, with inverted input and unity gain (for starting). But when I connect the output cap of the TDA1543 to the input resistors of the opamp the sound becomes very degradated and with a lot of hum. I tested both the outputs of the dac and the opamp. I believe that I grounded well everything, so there must be other problem...

Miguel

Hi Miguel, I connected the opamp just as in the datasheet of the TDA1543. The optional resistor at Vref is 3k3. For a start you can use the resistors as in the datasheet. The DC-blocking cap is after the opamp!.

[miguel2]

Like this? Isnt this active I/V conversion?

Miguel

[Elso Kwak]

Originally posted by miguel2
Like this? Isnt this active I/V conversion?

Miguel

Exactly,
Yes that's active IV-conversion

[miguel2]

Here is what I used. After the output cap I think I can connect any opamp there, like the opa549 from the gainclone that works well. So the opa134 should not give problems. I tried to use the Vref of the dac in the + pin but had no changes. time to think a bit more...