Yes, you can, as long as you understand a few details.
You’ll need a quality step-down transformer with the correct power rating and voltage for a start. Such a step-down transformer should be sourced from a quality local manufacturer like Tortech. It should be rated to deliver 1.5 to 3x the rated maximum continuous power consumption of the attached equipment. It must also deliver the exact voltage needed by the equipment.
This means that 100V-rated equipment needs a 100V step-down transformer, rather than the 110V or 120V offerings commonly available. Make sure you know which one you need, as indicated on the placard on the rear of your equipment. Avoid cheap Chinese transformers as these are usually incorrectly rated for both voltage and power.
If you have a powerful amplifier, you’ll need a huge step-down transformer to power it and for this reason, amplifiers are the least well-suited for use with step-down transformers. For low-powered equipment like turntables, DACs and preamps though, a small step-down transformer will work very well.
NOTE: You must never plug equipment rated to run on 100V or 120V into an Australian 240V mains outlet unless it has been set to run at this line voltage. This may require internal adjustment, soldering and almost certainly new fuses of a lower current rating given the higher line voltage.
Failure to adhere to this procedure will result in the death of your equipment.