The TORII MK4 has been replaced with the TORII MK5. It is enough of a change, that MK4's can not be upgraded. The MK5 is a different amplifier.

The output transformers have been upgraded to the UFO's, and the input stage is now the same as the Zen Mystery Amp.

There is also a meter for tube bias,  dual volumes, optional XLR inputs, and a variety of other enhancements.

We are in the process of upgrading the TORII page at the time of this post.

- Steve