Q:

LED Bike light - blowing at high speeds?

My bicycle is equipped with a about 5 year old hub dynamo and a LED front- and backlight.
I suspect the dynamo is a DC-generator though this likely may be false. But if its true, it would mean that with rising rpm I have rising voltage as well, which probably could cause some trouble at really high speeds. 
My question is: Would going fast enough on my bike make the LEDs (or other parts of the lighting system) blow? What are feasible ways to test if the dynamo output voltage is limited?

A:

Most dynamos produce a dirty 6v AC, depending on how fast you are going. I don't know how they've done it, but the engineers responsible for your bike lights probably included some rectification to convert the AC to DC and maybe even integrated some circuitry to limit the voltage/current going to the leds.
TLDR; No, you'll be fine.
So, if you wanted to make your own bike lights:

assume your dynamo outputs 6ish volt AC or more or less
convert this AC to DC with a bridge rectifier
add a big capacitor to smooth out this really sketchy power source
hook up your LEDs and resistor(s) in a way that they will survive the most extreme scenario
OR
come up with some voltage/current limiting magic

