DIY TDA1541A PCB "D3"

[ryanj]

Hi Steve,
Would something like this work?
https://github.com/iancanada/DocumentDownload/blob/master/Adapters/46A_DDDAC_UFL_Adapter.jpg
Are you planning on running in simultaneous mode, or I2S?
D3 is optimised for simultaneous data input.

 

[nopants]

Hi Ryan, is it possible to run sign magnitude with your boards? I'm still working through the thread but it seemed like it might be faster to just ask.

 

[ryanj]

Hi nopants,
Yes, two D3 boards should allow for this but I haven't made an I2S to sign magnitude convertor board to confirm.
Member kolby was attempting this a while back but I recall he was having an issue with a glitch at the zero point crossover, im not sure what the outcome was. Does anyone else know? I'd consider making a board for this as im pretty curious about it too.

 

[Supersurfer]

what is the difference between sign magnitude and running two dac boards (each dac chip one channel) in simultaneous mode?

 

[Brijac]

One more bit 😁

 

[ryanj]

what is the difference between sign magnitude and running two dac boards (each dac chip one channel) in simultaneous mode?

Here is Johns explanation.

 

[Supersurfer]

Isn’t this the same as your I2S-SIM pcb and using 2 or 4 d3 boards?

 

[ryanj]

No its quite different, sign magnitude splits the positive and negative parts of the waveform to avoid a situation where 1111111111111110 changes to 0000000000000001 at zero point crossover. One DAC for positive half and one for the negative half - one 1541a chip per channel.
The I2S2SIM v1 board converts I2S to simultaneous data.
The I2S2SIM v2 board has the same as V1 with the addition of data inverters so the dac can run balanced.

 

[Supersurfer]

Ok, clear. Than please built such a pcb for us poor sufferers that must cope without it 🙏🙏🙏😉

 

[nopants]

I'm just getting around to getting (re)acquainted with these boards again, am I understanding correctly that the current offset on the analog outputs is zeroed with a trimpot? Did you opt for this after comparing with a CCS solution?

 

[ggetzoff]

If you use the onboard IV the offset is zeroed out with the pots. It’s an an excellent and simple OPS.

However, many of us have skipped it and gone with off-board solutions. In my case, a hybrid SS-tube OPS.

 

[ryanj]

Hi nopants,

Yes I tried jfet current source, mosfet voltage controlled current source using the k216 as ECdesigns suggested many moons ago.
In the end the conclusion for myself was a fet used in this way sounded slightly grainy in comparison to a simple resistor, pot, and cap.

 

[ggetzoff]

Ben Mah uses a wire wound (hand wound) resistor in his setup. Probably the way to go as Ryan stated. Simple and good wirewound can have the harmonic signature for this type of situation. Maybe not even the lowest distortion resistor is what you want. Fun to try different types.

ECdesigns has a white paper of picking the value and the distortion plots.

 

[ryanj]

Also a nice article here with distortion measurements.
TDA1541 I/V Resistor Selection

 

[nopants]

Thanks for the insights, I was going to try some off board I/V's and it seems like I can do that easily just by adjusting the trimpot and not populating the on board I/V resistor.

 

[nopants]

Referencing https://www.diyaudio.com/community/...ate-nos-dac-using-tda1541a.79452/post-5718455

@koldby did you ever get sign magnitude fully working for your TDA1541A implementation?

 

[ryanj]

I've updated the opening post to include the layer stackup of the D3 in pdf.

 

[skilion51]

hello @ryanj
Can I still buy it?
Do you have the d3 and I2S to SIM in stock?

 

[ryanj]

Yes still have some, please check opening post for links.

 

[skilion51]

@ryanj

I just submitted a PCB Order Form.
Thank you.