What are matched valves? Does balance in a fixed bias PP amplifier matter? Quick matching of valves for the 50w monoblock's & testing an unbalanced OP stage.
Cheers for doing that video Andy, that subject has been on my mind a lot regarding “matched” pairs and how important it is. Your experiments / tests have proved it seems not? Looking forward to the sound tests, bung a bit of dub on! : ))
No worries. As I said when you buy "matched" pairs or quads I've not seen a seller spec what %age, Va, Vg1k, Ik or gm. Also the matched quads I've bought in the past weren't matched when I put them in an amp. I had to get in touch with the seller & spec the test conditions/match them myself. But as you've seen, does it really matter in terms of THD %? It might make more of a difference in an amp that uses one common cathode R, like in a Quad 2, say for CMRR. Suggestions for dub tracks? Best dressed chicken in town? Prince Fari?
@@ianmorgan6104 Not heard that one, just listened to it, the version I found isn't the best quality, but yeh, not bad. I remember Roots, long time ago. I like the old stuff but quite like newer stuff like Sumac Dub - Jardin De Lucy.
The U.S. Military often had 50 or 100 hour burn in on certain tubes to stabilize them. Any tube is going to have characteristics changes as it ages. Yes, correct, you will run in circles trying to match tubes and still never really succeed. There was quite a discussion on "Matching" tubes I read. Some sellers only match brands, some match date codes, and some match who knows what. I remember rebuilding an old Minschel organ as a Mothers Day surprise gift to my mother. My friend was an organ repairman and he saw my pile of new tubes for it. He told me don't put new tubes in, but put used ones in. If I had put new tubes in, he told me it was very likely he would have to retune it a couple of times, due to characteristics changing as they age. I installed used tubes, and the tuning stayed pretty accurate until she passed away, when I sold it.
Yep, Tektronix did too in their 500 series valve scopes. Made that mistake, pulled a 6DJ7/ECC88, put in a new one, scope didn't work. That's a grand story, TFW.
