Regulator on MGA

[Simon Matthews <simon.d.matthews@gmail.com>]

I have been bothered by a strange noise from my MGA recently. 

I think that the noise is the voltage regulator switching very quickly
-- creating a sound that is almost like a buzzing sound.

Is the regulator supposed to switch this fast? Or do I have a problem
with the regulator?  Any other ideas of causes for this noise? It
seems to happen only when the engine is revving above about 2500 RPM
and it does not seem to change tone with engine speed.

Regards,
Simon