Surfcaster said:
no soul said:
I'll try to keep it simple. The fact of the matter is there is a tolerance in bias when it comes to tubes. For example, A Mesa 6l6 STR425 itself even comes if various ratings. For Mesa, they declare these ratings by their color coded system. I forget exactly how they rank them, but there is something like 9 different ratings. The lower the rating the sooner the break up, the higher the rating the later the break up. Once again, this difference in dynamics is all for the SAME EXACT type of tube, from the SAME company and re-badger. The reason for this difference in rating is due to the tolerances of the manufacturer in howmuch exact power a tube may draw.
Now, consider the fact that almost every other company that rebadges tubes does this, I dont see what the difference is! Be it Groove, Ruby, Eurotubes or whoever, they test AND match their tubes for duets, quads, sectets, whatever the hell you need, for AMPLIFIER use, meaning that their tubes are going to be well within the tolerance level of a Mesas mesa boogies fixed bias rating. At worst, it may run a little hotter or colder than any of Mesas offerings, but its not likely to be a very big difference, besides perhaps a slight (but undectable to the vast majority of guitarists) difference in dynamics, and a perhaps a very slight difference in tube life.
Also, IVE NEVER EVER EVER EVER heard of anybody damaging a boogie from using non-Mesa tubes that were still in the correct family of tube required for their amp.
I will point out this being the case for the Peavy XXX, which apparently gets burned from using JJ E34L tubes, yes, E34L, not EL34. But once again, which was a result of Peavy using cheap components. But again, this is practicaly unheard of for other amps, Especially Mesa.
Think about it, this ploy of Mesas is almost a contradiction to one of their strongest traits, ROCK SOLID RELIABILITY! You mean to tell me this thing can take a nose dive off a 10ft stage at full volume and not miss a note, but the components cant handle non-Mesa badged tubes??
Thanks for "keeping it simple" for me, but, no, I'm not wrong...I stand behind everything I said.
If you've done any reading at all on biasing amps, you know that if your tubes are too far out of bias, not only will your amp sound bad and your tubes wear out faster, but you can damage the output transformer as well...a pretty costly "oops!" And that doesn't have anything to do with the quality of the amp...it's the laws of electrical physics. Granted, tube amps are generally forgiving in this area, but the risk is real nonetheless.
Further, tube breakup and bias are not identical...even within spec, you'll find tubes have different "breakup" points.
Reading through the Mesa literature, you can also find that Mesa only sells a fraction of all the tubes they test...because most of them are too far out of Mesa's specs. Sure, all tube re-sellers test their tubes and discard tubes, but they discard a much smaller percentage because with many amps, the plate voltages and currents can be adjusted to work with the tubes. Mesas can not be adjusted in this way. So common sense tells you there are many tubes in the correct family of tubes out there that you shouldn't put in your Mesa.
Now, as I said before, this does not mean you can't get tubes from other retailers that will work with your Mesa...you can...but you just want to be careful and make sure they know that you're putting these tubes in a Mesa. Besides, it's your amp...you're free to do what you want with it, but just realize that you may void your warranty and you may not be able to hide it from Mesa if something goes wrong.
You can't really adjust the plate voltage with a bias pot. Sure, when you adjust the bias pot, the plate voltage will fluctuate a little bit, but it isn't significant. There are a few ways to adjust the plate voltage of an amp and several Mesas have either one or two of these options happening.
(1.) A Variac switch will lower or raise the plate voltage depending on what setting you're in. The Dual and Triple Rectifiers have this option (Bold/Spongy switch) and the Mesa Mark Series have this option as well with their Tweed and Full Power modes.
(2.) Different types of rectifiers can change the plate voltage. The Dual and Triple Rectifiers will have anywhere from a 50 to 60 volt difference in the plate voltage when swapping the rectification type. Then, add the Bold/Spongy Mode into the equation and you will see anywhere from a 70 to 110 volt difference in the plate voltage.
So, as far as tubes being out of spec in a Mesa, they will work correctly, as far as Mesa is concerned, in some modes of their amplifiers. Will it sound the same? No it won't because hotter tubes will have more compression and will have less dynamic touch sensetivity. They will also sound cleaner and take longer to break up. Cooler tubes will break up faster, have more dynamic touch sensetivity and will be less compressed.
The descriptions above are based off of a power tube operating in it's normal bias range. The "Normal Range" being biased up anywhere from 60% to 75% plate plate dissipation. Most of the Mesas are biased so cold in Class A/B that you probably won't be able to tell much difference as far as the dynamics are concerned. The cooler tubes will be ratty and cold sounding, the tubes that fall within the Mesa spec range (aka Middle range or middle tier) will sound the same pretty much and the hotter tubes will be just as compressed as both ranges mentioned below. The only thing you're going to notice is just a tad bit more clarity when you progress from colder to hotter.
Lastly, Mesa's matching is fairly spotty. I've had tubes from them that biased up within 3 mA of one another, which is perfectly fine because 5 mA is acceptable, yet I've also had pairs of their tubes that biased up 7 to 10 mA apart.
I would rather get my tubes from another vendor. 9 times out of 10 when an amp goes down from a power tube failure, the screen grid resistor will go and the mains fuse will short to keep the Output Transformer from crapping out. A screen grid resistor costs anywhere from 50 cents to $2.00 and takes about a minute to install.
Dale
