I'll let you know as much as I can about my actual setup (it will be important to achieve a conclusion about my problem).
First, I have a ADAU1701 on a board that I designed. I'm using all ADC and DAC, one of MP pins I use for an digital external volume pot.
The ADC0 is my main input, receiving a balanced signal from my audio interface. I put two ampOps before DSP for a few reasons. First is to receive balanced signals (ofc), second to protect the DSP in cases of surge (rare cases but they happen).
The ADC1 is a generic input, for tests, phone input, etc.
The DACs, I use to send audio to a dual TPA3116 board (2.1). DAC 1 to Mid | DAC 2 to High | DAC 3 to Low.
At output, I use a active output filter like the datasheet, and another ampop to gain stage. (I prefer to do analogic gain over digital gain inside the DSP).
OK, now the power supplies
The supply is provided by a switched 24v/15A (generic chinese but with good and double core filters), and for +/-15v, I'm using two LM2596. One of then I put as inverting configuration (It does a regulator and a negative supply.. I'll show).
To make 5v, I use a LM7805 from +15v, simple and basic.
3.3v from a LM1117.
AND THE PROBLEM:
After a while (about 30mins) my output start with a little distortion, until the output is completely distorted and the audio pratically disappear after a few minutes.
Things that I already tried:
-Change the PLL_LF caps (same value, different materials)
-Place a 2.2uF and 100nF caps at Reset pin
-More capacitance before and after 3.3v regulator
-Another VDrive transistor (Same BC327)
-Make a new sigmastudio project from the scratch, nothing changed. A simple bypass (input->output), nothing too.
Ah, PS.: when fully problematic signal, I do a simple pertubation (touch with my fingers any V+ pin) and everything back to normal.
In Attachment, the files you need to analyze the case.