Preamp Output Completely Different with Tube Amplifier versus Solid State Amplifier

I had what I believe is an interesting occurrence with my Lamm LL2.1 Deluxe tube preamp driving 300B SET amplifiers (Air Tight and Elekit) versus driving a Nelson Pass First Watt F7 amplifier. Speakers are Charney Maestros with Voxativ drivers. Sources are Audio Note DAC and Thoress phono preamp.

When connected to the Air Tight ATM-300 amplifier, the Lamm preamp resulted in a fair amount of tube rush (audible from a couple of feet away). The amp by itself (with the preamp muted) had hardly audible tube noise. In addition, I rolled a number of 12AU7 tubes (the signal tubes) through the Lamm and nearly half resulted in some level of microphonic noise. Some very faint, some fairly loud.

As an experiment, I replaced the Air Tight amp with an Elekit 300B amp. By itself, the Elekit was dead quiet. With the Lamm preamp connected, the same levels of tube rush and microphonic noise as with the AirTight resulted.

BTW, both amps with the Lamm preamp sound absolutely wonderful, in spite of the tube rush noise!

At this point, I am thinking that the Lamm preamp is just extremely sensitive and transparent. So I now replaced the Elekit amp with a First Watt F7 solid state amplifier. DEAD QUIET! Absolutely no background sound by the First Watt amp, with or without the Lamm preamp connected. And no microphonic noise either! Sound quality is still great.

So, I am curious what might be the technical explanation for this phenomenon? Are the tubes in the amps and preamp reacting with each other such that unwanted noise is transmitted, whereas the solid state First Watt somehow blocks the noise? Is the First Watt not as transparent as the 300B amps?

Can you technical gurus explain what is going on?

Thanks for the help.

  -Gareents