ProtoDAC TDA1387 X8 project

[hifinet]

If there is an individual chip on the module that is failing, you could try to connect ground to each individual pin 7. I have never done it, but according to TDA1387 expert Abraxalito over at diyA, this will drop the output of the selected chip. He recommended this method for finding the bad chip in a stack (see below). If you find a bad one, you might try resoldering the leads on the chip or replacing it if you have the skills to do that.

Regarding the pin 7 caps, they can be removed entirely. Abraxalito designs do not use pin 7 caps. Pin 7 is left disconnected.

[Patolog1964]

Thank you for the information. It is terribly difficult to find such a defect. It manifests itself very sporadically.
Have you ever tried connecting two modules to each other? But I don't know how I2S would have to be solved.
Best regards, Roman

[hifinet]

Yes, I have stacked two modules, and it works fine. I removed all of the pins (clipped the plastic and individually desoldered the pins) and then soldered wires at 1,2,3,5,6,25,28. There is no problem with I2S. I did not hear much of an improvement compared to just one module, but admit that this was early on (before Z-foil I/V resistors). You could stack even more, I think. You just need to reduce the I/V resistor. I think Abraxalito has paralleled 128 chips. There is a theoretical 3dB reduction in noise for each doubling, and output impedence is lowered.

[MarkC568]

Off topic, but from reading diyA posts on instability problems with Ali tube amps, incorrectly labeled output transformer leads seems to be very common. Usually the primary leads are reversed, which causes positive feedback and oscillation. Best to have a dummy load on first power up.

Was my first experience with any kind of tube gear, so did a lot of research before the build. 

Initial power up was gradual with a Variac, dim-bulb tester and resistor dummy loads. 

Once all seemed/measured good at full supply voltage, I next connected a set of sacrificial speakers.

[rh2018]

Merry Christmas Mark and a big thanks for introducing ProtoDAC to the moOde community
Richard.

[hifinet]

Hi Richard,

Merry Christmas to you as well.

[OnkelPH]

 
 
I'm new here in the forum and started my ProtoDAC journey now in 2024. Most of the parts are in place so I can't wait to get started. 
Thank you for all the knowledge you have shared

Per

[OnkelPH]

Started the build and I have soldered on some pin connectors so that I can replace components more easily. These are the components and values so far:

I2S: 470R metal film (have a couple of 430R on hand)
I/V: Z-Foil 430R (Thay measure 429R)
Electrolytic decoupling: 1000uF 10Vdc Panasonic FR-A (Thay measute 889uf: someone with similar experiences????, they are the preferred ones!) I have other ones on hands (1000uF 16Vdc Elna Silmic II,1000uF 10Vdc Nichicon KA,1000uF 10Vdc Panasonic FM and thay at measuring spot on.)

That's it for now.

Per (Norway)

[hifinet]

That sounds good for the I2S resistors (430R or 470R works, maybe even down to 120R, but I haven't tried). I think the I2S resistors attenuate reflections and noise on the I2S lines. Without them, it can sound like an AM radio barely tuned into the station. A lot of noise with music in the distant background. Test that it will convert bitrates up to 384k.

The I/V of 429R should work with most of the modules. Some modules with higher output might clip at 0dB. As the power supply voltage increases, the output current of the module (and voltage at the I/V resistor) increases, so you will want to keep the power supply voltage close to 5.0 VDC. 

As far as the C3/C4 decoupling caps, you will need to listen to them and see which ones you like best. The Panasonic FR-A that I like are 1000uF and ESR of 41 mOhm (EEU-FR1A102L Digikey part P14378-ND ).

In my experience, when the capacitance is too low, dynamics and bass worsen. When capacitance is too high, the soundstage (depth) flattens.

When the ESR is too low, the sound is very accurate with large soundstage, but intolerably gray and sterile sounding.  Too high and the soundstage collapses.

Please share your experience.

[OnkelPH]

---

That sounds good for the I2S resistors (430R or 470R works, maybe even down to 120R, but I haven't tried). I think the I2S resistors attenuate reflections and noise on the I2S lines. Without them, it can sound like an AM radio barely tuned into the station. A lot of noise with music in the distant background.

The I/V of 429R should work with most of the modules. Some modules with higher output might clip at 0dB. As the power supply voltage increases, the output current of the module (and voltage at the I/V resistor) increases, so you will want to keep the power supply voltage close to 5.0 VDC. 

As far as the C3/C4 decoupling caps, you will need to listen to them and see which ones you like best. The Panasonic FR-A that I like are 1000uF and ESR of 41 mOhm (EEU-FR1A102L Digikey part P14378-ND ).

In my experience, when the capacitance is too low, dynamics and bass worsen. When capacitance is too high, the soundstage (depth) flattens.

When the ESR is too low, the sound is very accurate with large soundstage, but intolerably gray and sterile sounding.  Too high and the soundstage collapses.

Please share your experience.

Thanks for shairing your knowlage Keep you opdated.