BAT VK-500 protection circuit upgrade?



BAT offers a 'bias and protection circuit upgrade' for the VK-500.

Anybody have experience with this non-mandatory option?

Thanks
akaddict
I had this done a few years ago when I kept blowing fuses..email Viktor and he'll advise you.
I have mine upgraded. It costed me $500 + original box + shipping. I didn't hear any sonic difference.