Just a couple things to check, if your attenuator clicks when you turn it, make sure your attenuator is set to about 4pm when using a pre-amp, the manual says 12 or 1 but that's for the unit that does not click when you turn it.
Also, carefully look at your input tubes, be careful of too many Telefunkens or Siemens, they can be on the lean side, look at cableing as well, silver is not where you want to be with this set up, nor unshielded IC's
The ZH-270 is DC coupled, so bass cannot be matched by any transformer coupled amp.
But if change is what you want, drop me a note privately, I'll be more than happy to buy your amp :)
Also, carefully look at your input tubes, be careful of too many Telefunkens or Siemens, they can be on the lean side, look at cableing as well, silver is not where you want to be with this set up, nor unshielded IC's
The ZH-270 is DC coupled, so bass cannot be matched by any transformer coupled amp.
But if change is what you want, drop me a note privately, I'll be more than happy to buy your amp :)