Lew, I was not trying to imply that loss of vacuum in tubes happens quickly, I was only saying that it can happen gradually over time, as in years. But it does happen and the internals of the tubes do also alter with time due to heat as tubes get very hot like a light bulb. I have used tube testers also as you have and there is a reason we had those; it’s because we had to test the tubes for being in specification. If power amplifier tubes are driven too hard, the plates will melt, or they will warp simply with extended use.
I had a ceramic GU74B go out of spec slightly a few years ago in an Acom 2000A linear amplifier. I knew something was up as the stack temperature on the cooling was changing. I had a 3 to 5 degree temperature differential between the two tube pair. The more the amp was driven, the higher the differential and I didn’t like that as it meant one tube was doing more of the work to make output which would eventually cause it to fail (and these ceramic tetrodes are very expensive). My friend who was the US importer for this piece of gear drove up for a visit from Boston with a box of new GU74B’s; we swapped the tubes around for an hour until we found two which were very well matched and then did a realignment of the screen current to dial things in. Now the two tubes run within a degree of each other under most all conditions, even when driving the output to 2.5KW.
As I have said, I have enough issues with tubes and when I run my audio system, I would rather not be dealing with them. I much prefer high efficiency SS amps and preamps..... I love my pair of Anthem M1 monoblocks in proprietary Class D. They make no heat, are super quiet, have immense power at 2000 watts per channel and more depending on the load, liquid cooling on the output devices and they are silky smooth on upper end unlike some class D’s I have used. Anthem has their own class D circuitry which is patented; they do not use any of the standard D modules which most of the other Class D amps use. I have a Parasound Halo A51 which runs in Class A and A/b which is a very nice amp, but next to these M1’s, there just isn’t any contest. The M1’s blow the Parasound Halo out of the contest in performance.
Having 2000 watts per channel in an audio system is something which is truly wonderful. The headroom is outstanding, no distortion at all, no clipping and outstanding dynamic range/power. When I first installed my M1 pair and fired it up, it was jaw dropping. My friends at Axiom Audio (the guys who build Bryston’s speakers) keep trying to get me to bring in a pair of the Bryston 28B3 monster mono blocks.... I would love to as they run around 2000 watts each into 4 ohms, but I cannot justify the cost of the amps and question how much better they could be vs. the M1’s. If someone wants to lend me a pair to test for comparison, I’ll be happy to :)
I had a ceramic GU74B go out of spec slightly a few years ago in an Acom 2000A linear amplifier. I knew something was up as the stack temperature on the cooling was changing. I had a 3 to 5 degree temperature differential between the two tube pair. The more the amp was driven, the higher the differential and I didn’t like that as it meant one tube was doing more of the work to make output which would eventually cause it to fail (and these ceramic tetrodes are very expensive). My friend who was the US importer for this piece of gear drove up for a visit from Boston with a box of new GU74B’s; we swapped the tubes around for an hour until we found two which were very well matched and then did a realignment of the screen current to dial things in. Now the two tubes run within a degree of each other under most all conditions, even when driving the output to 2.5KW.
As I have said, I have enough issues with tubes and when I run my audio system, I would rather not be dealing with them. I much prefer high efficiency SS amps and preamps..... I love my pair of Anthem M1 monoblocks in proprietary Class D. They make no heat, are super quiet, have immense power at 2000 watts per channel and more depending on the load, liquid cooling on the output devices and they are silky smooth on upper end unlike some class D’s I have used. Anthem has their own class D circuitry which is patented; they do not use any of the standard D modules which most of the other Class D amps use. I have a Parasound Halo A51 which runs in Class A and A/b which is a very nice amp, but next to these M1’s, there just isn’t any contest. The M1’s blow the Parasound Halo out of the contest in performance.
Having 2000 watts per channel in an audio system is something which is truly wonderful. The headroom is outstanding, no distortion at all, no clipping and outstanding dynamic range/power. When I first installed my M1 pair and fired it up, it was jaw dropping. My friends at Axiom Audio (the guys who build Bryston’s speakers) keep trying to get me to bring in a pair of the Bryston 28B3 monster mono blocks.... I would love to as they run around 2000 watts each into 4 ohms, but I cannot justify the cost of the amps and question how much better they could be vs. the M1’s. If someone wants to lend me a pair to test for comparison, I’ll be happy to :)