Toshiba TB67S109AFTG microstep sine wave output current waveform captured with a oscilloscope using a current probe.
TB67S109AFTG is a 47volt, 3amp, up to 32 microstep driver that is fairly inexpensive. Individual drivers can be purchased on eBay for about $7. The driver output current waveform looks better than the TB6600. I think it runs stepper motors better than the TB6600 however it is limited to only 3amp output current. Many eBay listing for the TB6600 are actually TB67S109 chips inside the driver. If the driver has switch settings for 32 microstep, chances are it is a TB67S109 instead. The TB6600 is only a 16 microstep driver.
TB67S109AFTG 8 microstep 100rpm 12volts
TB67S109AFTG 8 microstep 100rpm 24volts