I carefully inspect all the Tubes I buy, I hear them one by one, match them in quads, and test them for minimum noise :
All Tubes have a serial number and a 6 month warranty should they become noisy or have a manufacturing defect.
I am more than happy to give you a discount if you can supply me with any tubes when I build your unit, as long as you provide me with two sets of four identical tubes, perfectly matched, none microphonic, and low noise, let me know before purchase.
Please contact me at POM AUDIO DESIGN if you need to get your Tubes tested and matched, it costs £100 plus shipment.
(it is free for all existing FAIRCHILD customers, of course)
If you need to buy any tubes, they can be directly bought here : https://www.jjtubes.eu/jj-6386-lgp-new
But make sure you match them in quads before using them in any FAIRCHILD.