The Dr. Z Z-28 amplifier was a 6V6 based circuit that utilized the preamp format of the Route 66. That is, an EF86 preamp, a unique Volume, Bass, and Treble full drive tone stack, and a tube rectified power supply. The Z-28 was rated at approximately 22 watts, so it fit under the Route 66 and the KT-45 in terms of output.
It had a more American type tone, which some had described as "Brown Tolexed Deluxe". The sweet sparkle of the 6V6 was ever present, along with a smooth full distortion at a very useable volume level. This Dr. Z design maintained a very tight bottom end, something that had been lacking in some 6V6 designs.
Like Dr. Z's other 3 knob amps, the treble and bass functioned normally until 12:00 and dial in gain once turned past noon. The stout, tube rectified power supply gave the Z28 a tight low end and made it very pedal friendly.