Fussbett wrote:

That piqued my interest until this:

The output tubes are 6BK5s. Obscure, yes, but great and forgotten. Phase inversion is done with 6GU7s. Various types are used throughout the preamp stages: 6AU6, 6BJ6, 6CB6, 6BN6, 5BQ7, 6AK5, and others. No 12AX7s, of ANY brand. How many tubes? TWENTY-THREE tubes in total. Including eight 6BK5 outputs. It might be the most complex tube guitar amp available today....

So basically fragile and expensive to maintain (after the $5000 price tag, of course).