Sibilance Problem on Digitized LPs

I'm fairly new at all this and am having a problem with excessive sibilance with recorded LPs. Currently not using any sort of DAC either in recording or playback (Is this the whole problem???). I'm using Audacity on a Mac running Leopard to record from a stock Music Hall MMF-5 turntable hooked into a BBE FJB-200 X phono preamp via a long run (25') of left/right RCA cable adapted down to the Mac's audio in pin connector via a Monster Cable RCA-into-stereo-pin-connector cable. These recordings are exported from Audacity into Itunes as either WAV files or AACs and both have the excessive sibilance. I've played around a lot with the level of the recordings but the sibilance problem persists. None of this is present on CDs I've ripped to Itunes with the rare inexplicable exception. Does anyone have any ideas as to how I might remedy this? Thanks.