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Difference between Class A, Class A/B


dennis138

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Originally posted by dennis138

I was looking at the new Peavey Valveking and there is a texture control that can be turned from Class A to Class A/B. I HAVE NO IDEA WHAT THIS MEANS!!!!!!!!! Just wondering if anyone could enlighten me.

 

 

something with the powertubes....I posted a thread on this awhile back and got some good replies...but in my old age, I can't remember what the hell the difference was =D all I know is that I use A/B on my recto selector...

 

also posted some clips comparing them, but I think you'll be hard pressed to find that much of a diference..

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I think I heard something about it phasing out the power tubes but I'm not sure. I'm wondering if it lowers the wattage or maybe acts like a built in Power Anntenuater like a Hotplate. It would be a KILLER feature if that's what it does. Plus, I'm amazed at how CHEAP the amp is!

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Originally posted by dennis138

I think I heard something about it phasing out the power tubes but I'm not sure. I'm wondering if it lowers the wattage or maybe acts like a built in Power Anntenuater like a Hotplate. It would be a KILLER feature if that's what it does. Plus, I'm amazed at how CHEAP the amp is!

 

 

definetly doesn't act like a hotplate, I can tell you that...and it doesn't act like a half power switch..something to do with tube efficiency I think? do a search if you have time...

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Originally posted by dennis138

I was looking at the new Peavey Valveking and there is a texture control that can be turned from Class A to Class A/B. I HAVE NO IDEA WHAT THIS MEANS!!!!!!!!! Just wondering if anyone could enlighten me.

Take a look at this white paper from Randall Smith: Class A - Exposed and Explained

 

I'm not sure the Valveking actually changes from Class A to A/B as per the normal definitions, but the most important thing to keep in mind is how it sounds to you. Peavey may just be using the terms for marketing, but I

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Originally posted by hal9000

Take a look at this white paper from Randall Smith:


"This is one reason why all Mesa/Boogies come with the bias permanently wired to the correct setting, to maintain this sweet spot within our range of power tubes."

I would bet the #1 mod to Mesa is a bias pot :D
Otherwise good link!

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One more time.....

Class of operation doesn't mean squat, tonally.

If there is any change at all to the tone from the switch, it is due to different paramters, such as reduction of plate to cathode voltage, cathode bias, etc.

No matter what their literature says, you can be sure it really isn't "Class A." Virtually nobody makes one. Again, not that it makes a difference.

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Originally posted by guitarzan


"This is one reason why all Mesa/Boogies come with the bias permanently wired to the correct setting, to maintain this sweet spot within our range of power tubes."


I would bet the #1 mod to Mesa is a bias pot
:D
Otherwise good link!

I'll second your bet :).

Of course, there are lots of tube vendors that rate tubes well within Mesa's tolerances. So, changing tubes can still be as simple as replacing a lightbulb, even if they aren't tested by Mesa.

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