i have known kevin hayes since the late 1980’s - was an early owner of his 4-chassis pa90c el34/kt77 amps which put him on the map with TAS and Stereophile rave reviews back then when the accolades meant something substantial
i do agree that his amps over the years did not perform the same (each design had their pros and cons, specifically tied to the power tubes employed) but like all great designers they have a target sound character in mind
in kevin’s case i would say he tries to voice his amps to have an expansive image, a good deal of high end energy (for tube amps) to support the imaging/air, a silky slightly romantic midrange, and tuneful/middling to good (not great or very deep) bass.... i think his phi models tried to compensate with stronger bass from his successful earlier lines using kt88’s, but he lost some transparency and some midrange magic... i think his 300b based renaissance series are still his best sounding (most midrange magic, air, and ever slightly rolled treble)... but he has gone WAY up market in recent years ... i have not heard his more recent megabuck stuff which i am sure ’has it all’
i do agree that his amps over the years did not perform the same (each design had their pros and cons, specifically tied to the power tubes employed) but like all great designers they have a target sound character in mind
in kevin’s case i would say he tries to voice his amps to have an expansive image, a good deal of high end energy (for tube amps) to support the imaging/air, a silky slightly romantic midrange, and tuneful/middling to good (not great or very deep) bass.... i think his phi models tried to compensate with stronger bass from his successful earlier lines using kt88’s, but he lost some transparency and some midrange magic... i think his 300b based renaissance series are still his best sounding (most midrange magic, air, and ever slightly rolled treble)... but he has gone WAY up market in recent years ... i have not heard his more recent megabuck stuff which i am sure ’has it all’