Archive of the former Yahoo!Groups mailing list: Korg Poly800/EX800 Users

The final audio stage of the Poly 800 goes through a NJM4558 OpAmp.
The slew rate for this OpAmp is a little to slow to achieve a 20hz-
20khz Bandwidth reproduction, and normally when these are used for
audio, compensation capacitors ar used to make up for it's lack of high
end. The Final Opamp stage doesn't use these caps though, so it's safe
to say that the high end freq. responce of the audio outs are capped.

Well, no point in adding the compensation caps, may as well remove the
OpAmp and replace it with a socketed higher performance audio opamp
that doesn't need 'em, one also that has a higher Signal to Noise
ratio. So, Dis is how;

What you'll need;

-Solderin' Iron (30 watt or so)
-Solder, Desoldering Braid
-8 Pin IC Socket
-NE5532 Dual Opamp (Pin 4 Pin replacement of the 4558)

Ok;

First you need to locate "IC2" on the KLM-598 Circuit Board (This is on
the top half of the Poly 800 synth). Unscrew the KLM-598 board from the
Poly 800 casing and remove the ribbon cables from the sockets on the
board(This will allow you to completley remove the circuit board out of
the synth to work on). Using the delsolder Braid, desolder all the 8
Pins of IC2 (NJM4558) and remove part from the board.

Next, Solder in an 8 Pin IC Socket where you removed "IC2", make sure
the IC socket is facing the right direction (matching up with the
drawing on the circuit board). Now, carefull insert you NE5532 Opamp
into the IC socket (The dot representing Pin 1 of the NE5532 should be
inserted into the socket so that it is on the side of the IC socket
with the Dip in it).

Now screw the KLM-598 board back into the Poly 800 casing, reconnect
all the ribbon cables, screw your synth back together....and your done!

Hope it sounds all the more sweeter. If ya find you prefered the ol'
noisy low-bandwidth NJM4558, hey it's easy to remove the NE5532 and
stick the old one back in there, no harm a done :)

Seeya

P9