Direct upgrade for JRC NE5532 ?

[Ian Finch]

Here's an extract from BB's own datasheet dated 1992, for the OPA604 (and probably other Bifet Opamps too). The title may seem anachronistic in a technical datasheet but manufacturers ignore the subjective assessment of product performance at their own peril.

SOUND QUALITY
The sound quality of an op amp is often the crucial selection criteria—even when a data sheet claims exceptional distortion performance. By its nature, sound quality is subjective. Furthermore, results of listening tests can vary depending on application and circuit configuration. Even experienced listeners in controlled tests often reach different conclusions.

Many audio experts believe that the sound quality of a high performance FET op amp is superior to that of bipolar op amps. A possible reason for this is that bipolar designs generate greater odd-order harmonics than FETs. To the human ear, odd-order harmonics have long been identified as sounding more unpleasant than even-order harmonics. FETs, like vacuum tubes, have a square-law I-V transfer function which is more linear than the exponential transfer function of a bipolar transistor. As a direct result of this square-law
characteristic, FETs produce predominantly even-order harmonics.
Figure 10 shows the transfer function of a bipolar transistor and FET. Fourier transformation of both transfer functions reveals the lower odd-order harmonics of the FET amplifier stage.

The full datasheet PDF with BB's Fig. 10 spectral comparison graphs is here: http://www.mouser.com/ds/2/405/opa604-445587.pdf

 

[spirovious]

Thanks for replies.
I need to study opamps carefully before changing original ones.Any others things to consider?