In this case, how the 4558 is used, using a opamp with a lower S/N
ratio and higher slew rate is better. If you check the schematics,
the chorus circuit already uses Active Low Pass filters at the input
and output of the BBD (MN3209). The output of the Chorus circuit is
then mixed with the Bypassed audio into the Final Op Amp stage (IC2
NJM4558).
I thought myself that they may have left the compensation caps off
intentionaly to filter out artifacts of the Poly 800 (ie. Hiss,
Computer Noise ect.), but in replacing IC2, I noticed none of this.
The 4558 Opamp, think of it at a dual 741 (1us slew rate BTW), it's
got lousy specs. The slew rate of the NE5532 is 8 times that of the
NJM4558 & the noise floor is dropped. Why not go with the high
quality shite, the Poly 800 is capable of some cutting sound with
that filter, wouldn't you prefer at full 20hz-20khz sound
reproduction coming from her outputs?
P9
--- In korgpolyex@y..., ">>>marjan<<<" <urekar.m@e...> wrote:
>
> better opamp is not always 'better'
>
> slow slew rate 4558 at the chorus output filters down some of
> the noise/aliasing of bbd chip, so 072 will be less noisy itself
> but it'll pass more of the bbd artefacts. YMMV
>
> --
>
>
>
> marjan
>
>
> me : Marjan Urekar
> e-mail: urekar.m@e...
> s-diy : http://surf.to/marjansystems
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