Originally Posted by Xenophon
Well, everyone believes what he/she wants obviously. But my religion is that differences in amplifier topology (feedback/no feedback....), driver tubes used, different operating point of the tubes and the resulting load line , variations in output transformers....will have a seriously higher impact.
For instance according to a Tubecad simulation (found by many builders to be pretty much on the mark) for a triode-strapped KT88 you can get a second harmonics component (no feedback used) ranging from <2% to >10%, depending on the voltage, bias point, impedance match with the output transfo... I mention that tube because I'm modelling with it now but the point is: these factors are imo much more audible than small variations based on the age of the tubes etc.
But as I said, it's more of an art/religion than science at this point, it would take some double blind testing and I'm not the proselytising type.
Originally Posted by JamieMcC
Comparing a Mullard 6080 to a Mullard KT88 considering the price differences
Interesting and I am not disputing the above as I know it is correct from my own build experience.
One of the things I find interesting about the Valvo/Mov/GEC 6080 is that it is was manufactured in the same factory using the same plate structure as the highly regarded GEC 6AS7G which is sonically on a whole different level to its 6080 version. The two plate structures look/are identical except for the getters.
As this is a bb about 6as7g/6080 tubes in particular, observations, characteristics and discussion about this tube type are kind of what you should expect to see here.
Originally Posted by Xenophon
You're right of course, apologies.
Just wanted to point out that many other variables come into play, when I started out I was of the opinion that the tubes were the decisive factor, have learned a couple of things since then.
Please excuse me for butting in here, but my (most unexpected!) foray into 6AS7G land seems to have been the exception that (dis)proves the rule, and shows that your "starting opinion", Xenophon, was not entirely far off the mark...first a very brief history...
Although not in the same league as most of the other units in this thread, I believe my humble Little Dot MKIV SE has actually displayed the vast difference tubes can make...viz. after a year on the LD tube rolling thread, and having gone from stock EF91,92 & 95 drivers (mine being Mullard M8100) with 2x 6H30Pi-EH powers, thru premium 6DJ8s with (vastly overpriced) 6N30P-DRs, and 6SN7s as power tubes, the improvements have been immense...(we did, of course, have to modify tubes due to different pin-out).
But none of these has given the same massive leaps that came first with my C3GSs as drivers, and secondly a (lovely) pair of Chatham 6AS7Gs in the hot seat - hot being the operative word here! Amazingly, we only had to provide an external heater power supply plus tube adapter for the 6AS7Gs to be accepted... without an ensuing pall of smoke, lol.
I (and others - with the MKIII) have run our units for many hours now without any signs of objection...cases get quite warm, but nothing too drastic. And the difference from what the amps were originally designed around is nothing short of phenomenal.
And so we, at least, have been fortunate to enjoy units punching way above their weight...and the 6AS7Gs have certainly provided a magical, not to mention highly unexpected, boost to that enjoyment - testament to my opening statement...
Another point I personally found, given my particular set-up, was that contrary to skylab's findings at the start of this thread, the Chathams - for me anyway - perform rather better than the RCAs. Obviously, personal preference comes in here, along with driver choice and amp topology, but the Chathams opened things up noticeably, giving an even more "3D/holographic" soundstage and managing to bring out even greater (micro) detail, via instrument separation that gave a beautifully clear presentation, without sacrificing focus/imaging...a sound I had never thought possible from such a lowly machine...(Mind you, I have helped things along a little by providing a decent source - the ESS Sabre DAC in my Audiolab 8200CD - plus pure silver wire in all signal leads, including the HD650's cable and the tube adapters I made myself. A decent mains conditioner also helps, I am sure...)...Sorry if this is too off-topic!
Would like to just show you the results of the past year's experimenting...