What's causing distortion at musical climax?

Problem description:
When playing vinyl, I can hear distortion on otherwise "clean-sounding" records when the music reaches its loudest point. This happens most often with orchestral music when the full orchestra comes in loud.

I'm hoping some of you vinyl gurus can help pinpoint the offending component in my modest system.
I have a Technics SL-3200 turntable with a Ortofon OM-5 cartridge. The phono preamp is a cheapy from Radio Shack.

What component is most likely causing the distortion?
1) The record itself
2) The cartridge
3) The turntable
4) The preamp

Thanks for your help!
Mika