Building the ultimate NOS DAC using TDA1541A

[crobbins5421]

Oliver,

FWIW...the Ian PCM board (I think) will require separate imputs to L and R on the DAC chip. Might this call for a jumper?....

[wlowes]

Originally Posted by dvb-projekt

Thanks John!

I will build it up on a new RB module to test your recommendations.


Cheers,
Oliver

& Put the decoupling caps tight to the 1541a pins and I'll buy it

[-ecdesigns-]

Hi dvb-project,

For a quick verification if everything is correct!

Yes that should work.

BCK needs to be around 800mVpp (approx. 1.2V DC bias) without using an attenuator, so this problem has to be solved in the BCK divider circuit.

BCK overshoot (on the scope) is usually caused by an incorrect probe. One needs to use HF probes, something like this:

3GHz RF Probe

Scope bandwidth also has to be large enough, 100 MHz bandwidth would be acceptable.

I also suggest to "measure" with your ears after checking the signal with the scope. What looks good on the scope can still sound lousy

[-ecdesigns-]

Hi AudioLapDance,

You used pin recepticals for the 1541 on an earlier version of your DAC (v1.3?)

I simply removed them from an old CPU IC socket with gold-plated pins.

[dvb-projekt]

Originally Posted by -ecdesigns-

BCK is extremely critical, attenuators are best avoided here, even plain series resistors are a problem (noise). Best results can be achieved by using 800mVpp BCK signal (not derived from an attenuator) with less than approx. 300 Femto seconds of jitter, but this is kind of "problematic"

So simply remove the BCK attenuator and hope for the best:

- Remove 68R, 220R, 10mH choke and all 100 Ohm resistors. Feed source BCK signal directly to pin 2.

Originally Posted by -ecdesigns-

BCK needs to be around 800mVpp (approx. 1.2V DC bias) without using an attenuator, so this problem has to be solved in the BCK divider circuit.

In the upper post you recommed to cancel the BCK 5x100R att. and the complete divider circuit parts for the 1.2V bias.
Without all parts i have the full BCK output voltage from Ian´s FIFO at PIN 2 and no Bias...?
I think i have not really understood what to do...

[triode_al]

Originally Posted by studiostevus

It's on Dit is een site die niets technisch te vertellen heeft maar een site is van beleving met audio

He does like his SD player! Good to have such clients.
Interesting stuff: he also mentions to prefer TDA1543 over 1541 because it [might be] internally less jitter prone and without external jitter (like in Johns implementations) the DEM logic of the 1541 has no advantage. . .
Even though he boasts a non-tech site, it does sound techy . . .

[dvb-projekt]

Originally Posted by dvb-projekt

Without all parts i have the full BCK output voltage from Ian´s FIFO at PIN 2 and no Bias...?

I attached the BCK output signal from Ian´s FIFO.

[qusp]

looks better than that normally too, the roundover is likely a measurement artifact

[-ecdesigns-]

Hi dvb-project,

In the upper post you recommed to cancel the BCK 5x100R att. and the complete divider circuit parts for the 1.2V bias.
Without all parts i have the full BCK output voltage from Ian´s FIFO at PIN 2 and no Bias...?
I think i have not really understood what to do…

Resistive attenuators lead to less steep transients, this opens the door for trigger uncertainty in noisy environments.

That's why I suggested to directly connect FIFO BCK out to pin2. This is the best compromise given the practical drive circuit limitations.

I also suggest to use shortest possible connection between FIFO circuit and TDA1541A BCK input. With shortest possible I don't mean a few centimeters mut more like a few millimeters.

If you want to experiment with a BCK attenuator you could try a similar diode attenuator like with WS and DATA. The pull-up resistor value then has to be lowered to 120 Ohms. The resistor value needs to be as low as possible, but it's minimum value is limited by the typical 25mA max. output current of the FIFO reclocker.

[dvb-projekt]

Originally Posted by -ecdesigns-

Hi dvb-project,



Resistive attenuators lead to less steep transients, this opens the door for trigger uncertainty in noisy environments.

That's why I suggested to directly connect FIFO BCK out to pin2. This is the best compromise given the practical drive circuit limitations.

I also suggest to use shortest possible connection between FIFO circuit and TDA1541A BCK input. With shortest possible I don't mean a few centimeters mut more like a few millimeters.

If you want to experiment with a BCK attenuator you could try a similar diode attenuator like with WS and DATA. The pull-up resistor value then has to be lowered to 120 Ohms. The resistor value needs to be as low as possible, but it's minimum value is limited by the typical 25mA max. output current of the FIFO reclocker.

Thanks for the information John.