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.
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.