Hey,
I'm currenlty working on opl2 and opl3 projects 😉
maybe I can help.
It should be the same value as C7.
And I think this will be 2.7nF (maybe you can measure C7 to be sure).
LS-215 is a clone of the yamaha DAC yac-512m -- see pinout here :
YAC512m-pinout.jpg
If I see it right on the photo, your missing cap (C5?) is connected to CH2
and C7 is connected to CH1.
The missing C5 goes to ground (at the other side).
As you can see on the datasheet of the YAC512M, this is the sample-hold capacitor Csh :
CSH.jpg
Recommended value for the yamaha chip is 2700pF = 2.7nF
So probably this is what they used as well.
If you can, measure C7 :
if this is 2.7nF, assumptions should be correct.
if C7 is not 2.7nF, and the other side is connected to ground (I cannot see on your photo), then just take the same value as C7
good luck !
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