I've been trying to set the balance on my VR for a while just by ear. What is the proper "tool" to find the correct balance? The light seems to illuminate at different points around the dial so I'm unsure which is correct. Also, should the LED be lot at all times and stay illuminated under load, or should it only illuminate when the load is present? The bias on this thing seems to be finicky with the recent cold temps we've had and I'm trying to get it sounding good again.