PCM5102A: using with OPA1678: analog output not what I expected?

Lukas Sidlauskas

Part Number: PCM5102A
Other Parts Discussed in Thread: OPA1678, LM27762

Hi,

Sometime ago I asked you a question about possibility of using op-amp with PCM5102A to have higher Vrms at lower loads than 10k and you recommended me to use something like OPA1678 and provided me with this schematic:

I used this schematic in my updated application and powered it with LM27762 (I used LM27762 evaluation board schematic). Everything works as expected, now the silent places of the soundtrack are dead silent (no hums from amplifier or car's alternator), but the output now is even more attenuated than it was before when the output was directly from PCM5102A. Right now I have only ~800-900mV Vrms without anyload. Why is this so?

over 4 years ago

0 Paul_Frost over 4 years ago

TI__Guru 52663 points

Hi Lukas,

Did you confirm with a scope if there is some clipping on the output? How much load is on the output of the OPA1678? Are the values of the resistors and capacitors exactly as shown above?

Thanks,

Paul

0 Lukas Sidlauskas over 4 years ago in reply to Paul_Frost

Prodigy 120 points

It seems the problem was in the source, after I reconfigured it now I finally have 2.11Vrms at the output of OPA1678 when directly measuring with a scope (without the load). Is this what I should expect? It seems it's driving the car's amplifier as it should - now I have more power at lower volume.

0 Paul_Frost over 4 years ago in reply to Lukas Sidlauskas

TI__Guru 52663 points

Yes, 2.1VRMS is correct.

Audio

Audio forum

PCM5102A: using with OPA1678: analog output not what I expected?