Pedrillo,
The Prima Luna Prologue amps allow tube rolling (kt88, kt66, el34, 6550, etc)
which may prove very useful to you as you explore the "tube
sound" through Merlins. The speaker is amazingly revealing and will
change character with each roll - sometiimes subtly, other times pretty
dramatically. Even modest examples of each tube type will provide a taste of
that tube's sound without a huge investment.
IMHO, there are advantages and disadvantages to each output tube I've run
through the system. In my system, the KT88s provide unique bass impact
(for a tube amp) at the cost of some midrange nuance. The EL34s tip
preciisely the opposite way. Others fall somewhere in between. I've used the
Prima Luna 7/VSM combo for almost a year now (other amps slide in from
time to time) and I have still not been able to settle on a single clear winner.
My message here is that tradeoffs and personal preferences will likely play a
big role in your final decision and it may take some time to make a final
determination. Flexibility in output tube may be something to consider as
you choose an amp to start this decision process.
Good Luck,
Marty
