Hello,
I am currently trying to track down the cause of a noise issue in my application and was hoping someone could provide a suggestion or two, since I'm running out of ideas here.
I'm using the TPA2012D2 as a headphone amp. My circuit uses a CS4334 DAC to drive the TPA2012D2 in a single ended configuration as shown in the typical application circuit in Figure 33 of the datasheet for this part. The amp is configured for 6dB of gain, and its supply is decoupled exactly as shown in the datasheet. With no input, I am experiencing a degree of hissing in addition to a high pitched tone at the output. The headphones also generate a noticable amount of heat.
It should be noted that this tone does not exist at the input. I have tacked a headphone jack directly onto the outputs of the DAC and the audio sounds superb, with no heating and absolute silence when no input is present. The board layout accounts for mixed signal design, with the analog portion of the ground plane being mostly isolated from the rest of the circuit. A wide trace connects the two planes directly beneath the DAC.
I suppose one specific question I have is how square would we expect the output from the TPA2012D2 to be? My output has a very sharp initial spike which quickly settles, with smaller underdamped spikes occuring randomly across the flat portion of the signal. It is my assumption that one of these peaks (or some multiple of them) are the source of the "tone" I am hearing.
Thanks in advance for any suggestions as to what might be causing this!
