So I have a ground pin on the PCB.. When I measure it before the clocks are on, it measures about 0.9mv above earth potential (the earth connector of the IEC power supply). When it's decoding it goes up to 6.8mv.. So about 6mv increase.
That's probably OK. In case it isn't, you'd hear clicks on the audio outputs. Try adding the 2.5V series resistor (10R) and see if the signal dropout goes away.
Also, what frequency are you doing for the system internal clock ? Put your scope on pin 64 and check what freq you read.
Also, what frequency are you doing for the system internal clock ? Put your scope on pin 64 and check what freq you read.
unfortunately I don’t really have an easy way to add that as the 2.5V is on the board and it’s routes to the STA310 directly. On the next board I’ll add space for a resistor. Just to clarify, it comes between the regulator and the capacitor there, or between the capacitor and the load?
Yes, between the regulator and the capacitor. If this is not your final board, then you could cut a trace can't you ?
What about pin 64? (edited, read above)
What about pin 64? (edited, read above)
I dunno man, I’ve never cut a trace before. Where would I put the resistor? Like use a THT one somehow? I’ll have to look it there is anywhere I can attach it in the schematic. Or do you recommend scraping off the solder paste and doing it between the trace segments after I cut?
I’m not in front of it, but last time I checked LRCLK was 48kHz, BCLK around 3MHz and PCMCLK 12.3 MHz.
I’m not in front of it, but last time I checked LRCLK was 48kHz, BCLK around 3MHz and PCMCLK 12.3 MHz.
I don’t think it’s losing sync though. It’s not throwing any errors at least. I feel like when it stops it’s literally hung up, like a crash. But I’m not entirely sure. I may try to think of some debugging I can do in real time to see if it’s responding and put it on the LCD every second or so.
I can't probe that I don't think, I didn't bring it out to anything. I tried and I touched a pin nearby at the same time and it reset. So I'd rather not risk damaging it. On the next board I'll run it out to a header.
That resistor doesn't necessarily have to be THT, it could be SMD. See, I had similar issues before I added that resistor, the noise from the 3.3V digital power supply ended up unlocking the PLL by directly introducing noise into the PLL filters. It's important to have that. The 2.5V is what powers the SPDIF input circuitry as well.
If you can't add that, then try putting a large cap across the 1uF bypass, say like 100uF.
If you can't add that, then try putting a large cap across the 1uF bypass, say like 100uF.
Hello, I would like to know more about this board and how it works because I have pcb's and the parts for LM4780 2x60 watt and
LM4781 3x35 watt which makes 5 channel, but I only have knowledge regarding how amplifier works ,I don't understand stuff related with
software, would you think after you finish this project can sold some boards?
Regards
LM4781 3x35 watt which makes 5 channel, but I only have knowledge regarding how amplifier works ,I don't understand stuff related with
software, would you think after you finish this project can sold some boards?
Regards
The boards right now require some kind of microprocessor to function, so they won't function on their own. It's possible at the end I might be able to make a standalone board with a small microprocessor on it, but I'm a ways from that. But let's see where I get at the end!
Ok, I would like to know more understand how the interface will be made from the source player to the 5 channels, when you got the time.
I am curious for the end results because have everything ready regarding the LM4780 and LM4781 pcbs
Regards
I am curious for the end results because have everything ready regarding the LM4780 and LM4781 pcbs
Regards
I definitely want to try and help people like you, as I was in the exact same spot and there aren't really many solutions for this problem that don't involve a bunch of external hardware. So keep checking in and I'll see how things go.
So more good news.. I pulled my Bose computer speakers out from my office and set it up next to the STA310 and my PCM1681. I wired together a hacky 3.5mm cable to my DAC and hooked the Bose speakers up to it. The DAC is working! And it sounds good too, thankfully.. Phew. I don't understand why it looked so crappy on the scope, but it sounds decent hooked up.
Okay thanks if you wish something from me say it I have quite a good number of national semiconductor parts.
Regards
Regards
Congratulations on getting it to work !! 👍
What you were seeing was mainly out-of-band noise from the sigma-delta process. Like I said earlier, try turning on the oversampling ratio control (OVER = 1) on the PCM1681 to reduce the out-of-band noise further. That would also allow you to have a slightly higher cutoff frequency (30-35kHz) for the LPFs.
I did turn it on when you suggested it, and it’s still on. Right now the DAC output is not being filtered. I think the new filter boards arrive today. I’m using the opa2134. I built one previously but use an opamp from Aliexpress that I suspect was fake. So I ordered real opa2134s from mouser.
I’ll try the scope again after I filter it. I’m just surprised as on the datasheets that noise seems to be 60db down, even without filtering, so I don’t entirely get why it’s so prevalent on the scope. But I’ll try the scope again after I filter it. But it sounds decent. Only when I turn the Bose volume up real high and turn the volume off on Netflix do I hear a bit of junk in the backward (which I suspect is the OOB noise).
I’ll try the scope again after I filter it. I’m just surprised as on the datasheets that noise seems to be 60db down, even without filtering, so I don’t entirely get why it’s so prevalent on the scope. But I’ll try the scope again after I filter it. But it sounds decent. Only when I turn the Bose volume up real high and turn the volume off on Netflix do I hear a bit of junk in the backward (which I suspect is the OOB noise).