Actually the input of the "control" inverter comes from the DSP (high or low depending on program material) so only one diode string is polarized at a time, as I tried to explain before.
The problem is that I planned to have only one clock source in my DAC since I only have 44.1kHz/16Bit audio but also wanted to still be able to play different samplerates.
Looking better at the specs the WAP seems to be limited to 48kHz (so no 96kHz 😡) so probably it's not worth the extra hassle to add a second clock.
So the injectoin point is decided: Pin 1 of 74HC04
Still have to decide how:
1) removing the capacitor "C3" on the schematic (C123 on the PCB) and feeding the clock before the 100R resistor
2) lifting the pin 1 from the PCB and feeding the clock from there (maybe removing the 47k "feedback" resistor that would still connect pin2 to the oscillator.
In any case I will use a 74VHC125 buffer to feed the clock in (and to perform level conversion from 5V to 3v3) and to buffer the DAC signals (in case they are I2S) or the SPDIF (for other formats).
Ciao
Andrea
The problem is that I planned to have only one clock source in my DAC since I only have 44.1kHz/16Bit audio but also wanted to still be able to play different samplerates.
Looking better at the specs the WAP seems to be limited to 48kHz (so no 96kHz 😡) so probably it's not worth the extra hassle to add a second clock.
So the injectoin point is decided: Pin 1 of 74HC04
Still have to decide how:
1) removing the capacitor "C3" on the schematic (C123 on the PCB) and feeding the clock before the 100R resistor
2) lifting the pin 1 from the PCB and feeding the clock from there (maybe removing the 47k "feedback" resistor that would still connect pin2 to the oscillator.
In any case I will use a 74VHC125 buffer to feed the clock in (and to perform level conversion from 5V to 3v3) and to buffer the DAC signals (in case they are I2S) or the SPDIF (for other formats).
Ciao
Andrea
More updates:
I tapped the supposed I2S signals near the DAC and routed then, via a 74VHC125, to a DAC board.
Using a TDA1543 sound has a very low volume and is heavily distorted, so the format is not I2S
Using a TDA1545 sound seems OK so the format looks like EJAI.
Couldn't make more tests because the WAP suddenly decided to die...
Well it is not completely dead , logic works but when I press play there is no more sound (it stopped working without apparent reason while I was listening with the TDA1545).
While playing the display shows elapsed time... it seems freezed but looking better to change from 1sec to 2sec of elapsed time it takes more than 15 seconds.
Looking ad the digital signals with a scope bck and l/r are ok, data is no longer present.
For me this is the end of this project unless I find a way to fix this one.
Ciao
Andrea
I tapped the supposed I2S signals near the DAC and routed then, via a 74VHC125, to a DAC board.
Using a TDA1543 sound has a very low volume and is heavily distorted, so the format is not I2S
Using a TDA1545 sound seems OK so the format looks like EJAI.
Couldn't make more tests because the WAP suddenly decided to die...
Well it is not completely dead , logic works but when I press play there is no more sound (it stopped working without apparent reason while I was listening with the TDA1545).
While playing the display shows elapsed time... it seems freezed but looking better to change from 1sec to 2sec of elapsed time it takes more than 15 seconds.
Looking ad the digital signals with a scope bck and l/r are ok, data is no longer present.
For me this is the end of this project unless I find a way to fix this one.
Ciao
Andrea
That's a pitty. And i guess guarantee is also shot.... I hope you get it working again. Better reason for me not to hack mine and make a spdif dac with pll.
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