Regarding the TL084 (or TL072 which is more reliably quieter) these are at least 3x as noisy as the NE5532, which I have found to be much noticably quieter for audio applications. Also consider the OPA2134 as a superior lower noise op amp. When doing filtering you should use a high quality low noise op amp.
It's hard to find a good op amp in a DIP package these days, which is what I was hoping for. I may have to cave in and use a SMT part that has superior quality. I do love the NE5532 as a general purpose audio op amp. I might re-spin the PCB to take two dual op amp packages instead of one quad package. That would allow me to try the NE5532 or some other higher-quality parts.
Out of curiosity I looked up the noise specs of the two op-amps in question.
At 1 kHz:
TL084: 37 nV/root Hz
NE5532: 5 nV/root Hz
Yeah, you are correct, it's a huge difference. Now I'm definitely leaning towards trying a new op amp. Still going to relocate the AF filter in the block diagram to right before the audio PA.
Regarding the TL084 (or TL072 which is more reliably quieter) these are at least 3x as noisy as the NE5532, which I have found to be much noticably quieter for audio applications. Also consider the OPA2134 as a superior lower noise op amp. When doing filtering you should use a high quality low noise op amp.
Thank you, I appreciate the comment.
It's hard to find a good op amp in a DIP package these days, which is what I was hoping for. I may have to cave in and use a SMT part that has superior quality. I do love the NE5532 as a general purpose audio op amp. I might re-spin the PCB to take two dual op amp packages instead of one quad package. That would allow me to try the NE5532 or some other higher-quality parts.
Out of curiosity I looked up the noise specs of the two op-amps in question.
At 1 kHz:
TL084: 37 nV/root Hz
NE5532: 5 nV/root Hz
Yeah, you are correct, it's a huge difference. Now I'm definitely leaning towards trying a new op amp. Still going to relocate the AF filter in the block diagram to right before the audio PA.