Sophia Electric tube quality

I don't know that tapping on tubes will reveal any manufacturing flaw. I have two pairs of Sophia RP's bought here as a slightly used quad set. I use only one pair at a time. I've had them going strong for eight months with many hours and no problem. Mine are used in Wavelength Cardinal Signature XS monos.

I estimate something like a thousand hours on mine, and they've performed flawlessly. They are about 5 years old.

I should just add that as good as their tubes are their amplifiers are as good or better...They make a sweet little pair of 300B mono blocks that I used to drive a pair of Tannoy Kensington SE's to rock and roll volume in a large room with 10 foot ceilings. Not shy little flee powered.

You're indicating you think Sophia's response was disrespectful or something. Buy tubes from Kevin Deal, then call him and say you were thumping on them and you think they're microphonic. His response will burn a tattoo on your ears with unchristian language that may question your parentage and other cognitive abilities. I'd buy from him anytime and I own a Sophia amp (my second).

Tapping your thumbnail? Why don't you tap your cartridge or lick a hot tube?
Play the amp normally and see if it echoes or picks up too much noise.

I had no problems with my pair. And I found Richard et al to be very helpful and accommodating.

I had a faulty Royal Princess 300b tube and they replaced it promptly and were very polite, I was impressed. That tube had wonderful sound in my SET amplifier.

Elvick's suggested hot lick test would have no relevance as to a tubes performance, though could prove very useful in human IQ testing.

Despite your recommendation of not to tap the tube, well constructed tubes do not ring when tapped. 

Emission labs 300b XLS come with instructions never to tap on a tube that is in use.

If they won't let us tap an in-operation tube, can we at least "lick" them? 

I do not think it would have occurred to me to actually do either, and now that you bring it up ...I still won't.)