how much current does a yba 600 power amp provide.

The amp can make 300 watts into 4 ohms.

The power formula is Power = Resistance x current(squared).

So if 300 watts, divide by 4 (if that is the impedance of the speaker) and the result is 8.66Amps.

You may see much higher current ratings advertised by the manufacturer. None of this current will be used to drive the speaker- those numbers (like 80 amps for example) are how much current is present when the power supply of the amp is shorted out for 10 milliseconds. Its a rating of the power supply not the output section of the amp.

more:
http://www.atma-sphere.com/Resources/Common_Amplifier_Myths.php

I did a quick search on the internet & found an ad on Canuckaudio for a YBA Passion 600 for sale. It seems that this amp uses a 1KVA power transformer & is a 150W/ch into 8 ohms.
From my calculations, assuming a dual secondary i.e. it's a stereo power amp, max current from the power transformer is 14A per channel.
From Ralph's calculations it seems that the amp's output stage is configured to deliver such less than the max available (which is a good thing in that there seems to be some engineering margin in the power transformer).
Of course, impedance of the speaker is not constant i.e. varies with frequency. Plus, the impedance is capacitive & inductive over freq meaning that the amp will have to supply more current (into a reactive load) than what Ralph calculated (hence his comment of "if that is the impedance of the speaker").
These 2 calculations should give you a pretty good pix of what the amp is capable of & what its current delivery limitations are.

Thank you for your responses.