Amperex PQ 6922 vs Amperex PQ 7308

PQ and Non-PQ are the same tube. I've not heard consistant differences in sound between the two label types.

On the otherhand, in the gear I've owned, Amperex 6922 and 7308 sound quite different from one another. There is also a difference (in sound) between Holland and USA product with the same internal construction.

I've owned/tried approx. 100 various Amperex White label 6922's and 7308's in Audion and Consonance gear.

Same goes for Philips SQ and Non-SQ labels (based on sampling 20+ of their 6922's). They sound alike.

PQ = premium quality - it could just be a branding thing but then again it could be some extra selection for matched sections, etc. Likely impossible to say - much lore surrounding that sort of thing has been lost to the mists of time, alas.

-Ed

The Amperex 7308 was an attempt by manufacturers to make a tougher and longer lasting tube. This tube was made starting in 1959. The older the tube, the better the sound quality--or so they say. The white letter PQ with shield is the best sounding. They made a USA and a Holland version. The Holland is sapposed to be sweeter, but not quite as dynamic as the USA. Also, in 7308, they made an orange lettering/orange world globe logoed tube. I've tried this tube. It's better than the JAN green letter tube by quite a bit, but not as good as the PQ with shield. The JAN green letter is not as open as the two tubes above. Currently, I'm running four Amperex 7308 white letter PQ with shield in my Bat preamp. Good tubes make a huge difference.

I ran out of space on my last post-- As dogpile said JAN is military use. I've also seen JAN orange world globe logo tubes . I've heard that on earlier 7308 tubes, they may be white lettered only (and still be PQ) or they may be white lettered and say PQ but not have a shield. It's kind of a mess. Other manufacturers also put their label on these tubes as well. Sorry if I repeated some of the info repeated by others. Where's Joe when you need him? Dekay, have you tried any of the earlier 7308 Holland PQ tubes? How do they sound? Ive never had the chance to try any Holland version PQ's.

I hope that I didn't step on any toes by diving into this thread. I was just relaying what I've learned from Andy @ Vintage Tube Services and what I've learned in 6yrs of trial and error with small signal tubes. Ed- I read your review of the Shuguang/Super TNT 845B tube. It looks like you've been around tubes for a long time... as I said, I hope that I didn't step on any toes. Best! Stan