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Just picked up a NOS Mullard CV4003 again $$$$$
I just bought some NOS MULLARDS for the first time for the preamp of my HP Integrated.
12AU7s the M8136s... I bought 4 and replaced 4 of the 6 PL branded 12AU7s.
Wow, huge improvement in not only mid-range tone and texture, but especially soundstage.
Next, I'm about to replace the PL EL-34 tubes with some Gold Lion KT-88s in order to
increase dynamics, speed, and balance.
So what I'm saying is that the HP allows great rolling opportunities. The stock PL tubes (EL-34) and 12AU7s are fine
to get you going. I don't really like them, I thought they were rather stale in some ares with too much energy at certain frequencies.
But I think of the HP Int as a blueprint for which to fine tune the tubes to your speakers and ears.
Someone mentioned how the tubes lose power or refinement from the energy it takes to auto-bias.
The flip side to this is that if you toss the lame stock tubes, and invest in quality tubes,
then you have thrown down a chunk of change, the low demand from the HP tubes will allow a longer tube life.
The (proverbial) 10,000 hours instead of 2500 hrs.
But you get the point.