Expanding questions about tubes in a preamp

Hum is either a design or installation fault.
Hiss is a gain structure fault.
Microphonics are a tube fault.

IMO, chassis damping has more effect than tube dampers.

I first used VPI blocks on my Citation II in the late 70’s/early 80’s, whenever they became available. Blew me away. Been collecting more ever since.
Ditto support damping as seen here
http://www.ielogical.com/assets/M-125/VPIBrickDamping.jpg

NO ONE has ever failed to hear the difference!!

@OP - why such a cryptic topic?

@insearchofprat:
Why change the EF86?
Unless the unit has been left on continuously for 10 years, the tube should have plenty of life.
Putting back 12AU7 will reduce gain about 6db.

Hum could be failing PS in the Wolze.

How is the Wolze interfaced to the HTA-5550?

Have you 'backed-up' from the power amplifier with shorting plugs to see where the noise originates. By that I mean put shorting plugs in the power amp and see what noise appears in the speakers. Then add the next upstream device with shorting plugs.

Just FYI, about 15 years ago when I added HT, every Yamaha model I tried, about 6, hummed. I designed and built recording studio wiring, so it was not user error. Denon, HK, Pioneer, Onkyo were all dead quiet.

Since the HTA-5550 does not need a pre-amp to accept signal from the SA-8001, is the Wolze simply a coloration effect?

Have you tried running theSA-8001 digitally into the HTA-5550?

A  with tube damper testing is it is impossible to install / adjust them without moving the tube and refreshing contacts.

Dampers could work by two methods: Vibration control and resonance damping. Assuming the envelope vibrates, what happens? The tube is a vacuum and sound does not travel in a vacuum. It could damp sound, which has very little energy, from travelling down the envelope to the base and up into the electrodes. One should be able to mathematically calculate the energy required to vibrate the electrodes. If resonance damping is the m.o. then where the damper is placed will affect its utility. Since all tubes vary slightly, how does one know if the location is correct for the particular tube. Model or item. AT, AU,  AX, AY, BH // 66, 77, 88, 90, 120 150 for but two families.

It is quite trivial to set up a test wherein one records the output of a tube device w/wo dampers and delta the difference.

Since damper claims are anecdotal, I assume it's never been proven.

12AU7 mu 17 and requires a lot more input than 12AX7 mu 100.
Amplifier was designed for ????
Distortion in one case will be several multiples of the the other.
Perhaps the cymbal sparkle is odd harmonic?