From a console, run 'locate 1688'. It the driver is already compiled as a kernel driver, that will show it to you. If you don't have it. you will have to compile it yourself.
If you have it, it will look something like this:
/lib/modules/2.6.11.4-21.17-smp/kernel/sound/isa/es1688/snd-es1688.ko
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