While the "non A" version would work it would be unlikely to reproduce
the original design spec for the amp. The A suffix usually denotes a
device specified for audio or low noise applications.
That last statement is not always correct, it sometimes denotes a
higher Vceo or some other data.
Not to worry, down to more practical info.
The short form data I have indicates that the 2sd1569 has Vceo = 60V
and a high beta of around 800 and low Vce(sat) though I don't know
what the specific numbers are. The high beta suggests it would have to
be a darlington device. Nevertheless, if you can confirm that a device
with Vceo = 60V will suit your amp then might I suggest the Fairchild
KSD880
http://www.fairchildsemi.com/ds/KS/KSD880.pdf and its
complement KSB834 as alternative devices. You might even be able to
get some free samples from Fairchild.
