Tonal and power issue of the E acute string with K&K pure passive pickups

[Chuchi]

Hi,
Being a non-native English speaker, my apologies if I do not use appropriate technical terms.
Guitars
I do own several acoustic guitars with different type of pickups.

• A wonderful Ralph Bown 12 strings “Stella Leadbelly” guitar with highlander pickup.
• A Maple Jumbo guitar made by the famous guitar builder Alain Quéguiner with an active undersaddle fisman prefi piezzo
• A Martin OM-21 with a passive soundboard pick up from pick-up the world
• A maple 6 string with and active piezzo
• A nylon folk made by a lyuthier with a B Band
• A Froggy Bottom M in Koa with a K&K pure Western M Passive pickup
• An all mahogany Santa Cruz 1929-00 with a K&K pure mini pickup

Amps

• Acoustic image Corus
• Acoustic image Coda R + A Raezer’s edge Stealth 12 Cabinet
• A AER Domino 1st generation
• A Swart atomic space tone valve amp

Preamp
A radial tonebone PZ-Pre preamp.

The issue I do have to face concerns mainly the K&K passive pickups (excellent by the way).
While all the above-mentioned guitar are extremely well balanced in term of tone and intensity. However, once plugged into the acoustic amps, it appears that the High E string seems have less power and beautiful tone as compared with unplugged performance.
I would exclude a bad installation of the K&K pure mini or western pick up since they have been installed by different persons and different shops

I have tried the Radial preamp but - with the settings I’ve tried (and I’m far from being an expert) these guitars sound metallic and do not express their tonal qualities.

The main question I do have is: does someone have already been confronted to such situation
I’m not sure that the PZ-Pre is the best appropriate preamp for the passive pickups but before switching to another one, I’d appreciate to have the feedback of acoustic guitar players that have such passive K&K pickups.

So, any suggestions, advice or comments would contribute to reduce my stress regarding which workflow and settings I should use to benefit of wonderful qualities of those guitars

Thanks to the players that will dedicate a little of their time to help me understanding this issue.

Best regards
Chris