I measured my DAC output voltages for laser modulation and found something interesting:
Moncha: USB Powered, Max output 4.4v
Riya: USB Powered, Max output 4.4v: External P/S powered: didn't test.
Easylase: External P/S, 4.8v.
So, it appears that USB powered DACs might not be giving full output for laser modulation. At 4.4V, that is only 88% of the full 5v that is required for full power. So, 12% of laser power is lost right there! Depending on your laser module, you might be able to boost the laser driver output to compensate for the lower than ideal voltage. I can do that on my die4drive drivers. I can probably do the same on my Lasever but I am not going to touch it until I get it repaired or the warranty expires.
I normally don't use my EasyLase DAC because it requires an external power supply but there is definitely a reason for an external p/s as you can see. But even still, the EasyLase is only at 4.8v which is only 96% of ideal.