#1
so im in the market for a small all tube combo and was reading about the vk on harmony central. there was a statement made by a reviewer that said you can change tubes on the vk without rebiasing. is this true, can you really change the tubes on a vk without having to rebias it?
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Quote by Dempsey68
get a cheap marshall... my MG15DFX has a button that simulates the sound of one of the expensive tube marshall amps.
#2
someone correct me if i'm wrong, but i think you can change tubes on any amp without rebiasing them as long as the new tubes are the same exact ones as the old ones, but i could be wrong
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#3
yeah its like changing strings on a floyd. if you make a change in the guage, the actions gonna be all screwed up. so you replace with the same guage. if you change the tube type then you have to change what the amp expects the tubes to be.
#5
As long as you replace with the same tubes it doesn't need biasing. Some other amps do need biasing.
#6
I had been wondering this myself some time ago (I have a VK100 head), and from what information I can gather (it doesn't state in the manual), the Valvekings are "fixed" bias, non-adjustable. Meaning they can't be adjusted. Now, from what I understand, that means that you can simply switch the tubes, without worrying about biasing, as long as they're:

A) a matched set

B) the correct type (6L6gc, 12ax7, etc.)

I've also heard that they're fixed-bias a little "cool," probably to prevent from overheating a tube if you were to replace them with a different brand name.

I'm still looking to get a good solid confirmation on my information though.
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Last edited by Hakael at Nov 1, 2007,
#7
I do remember there was some self-biasing amp I played recently and that is one of them...
#8
^
Where did you get that info? I'd like to know. Reason being, I thought self biasing amps were limited in wattage and generally don't go above 30 watts. Unless the TS is talking about a Royal 8, the other Valvekings are 50watt (112), and 100watt (212, and VK100).
~We Rock Out With Our Cocks Out!: UG Naked Club.~
Once in a blue moon, God reaches down from his lofty perch, points at an infant boy and proclaims, "This one shall have balls carved out of fucking granite."
#9
To clear that up, I meant, "...that is one of them..." in the sense that, the Valveking is an amp I played recently.

However, I just checked it out and remembered it's the THD that is self-biasing.
#10
i was referring to the 50 watt 112^(2 posts up)^

thanks for the feedback, doods
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Quote by Dempsey68
get a cheap marshall... my MG15DFX has a button that simulates the sound of one of the expensive tube marshall amps.
#11
Quote by Hakael
^
Where did you get that info? I'd like to know. Reason being, I thought self biasing amps were limited in wattage and generally don't go above 30 watts. Unless the TS is talking about a Royal 8, the other Valvekings are 50watt (112), and 100watt (212, and VK100).


Traynor has amps that are self biasing and are more then 30 watts.

YCV 40

YCV 50 Blue

YCV 80
#12
Quote by stangconv
Traynor has amps that are self biasing and are more then 30 watts.

YCV 40

YCV 50 Blue

YCV 80


I wasn't challenging the other post, but was more looking for an explaination.

Although I did find this info from Michael Soldano on premierguitar dot com.

"Self-biasing", which is sometimes also referred to as "cathode bias", is nothing new at all, Doc. Nor is it a gimmick or anything all that remarkable, but there are some amp makers that want you to believe it's the greatest invention since the wheel. I don't have enough space here to properly explain what biasing is, and how it works. What I can tell you is that in guitar amps the two common methods of biasing tubes are self-biasing (cathode bias) as we're talking about here, and fixed bias. And the fixed bias can be adjustable or none adjustable - either way, it works the same. Generally, all of the preamp tubes in guitar amps are self-biasing.

It's in the power section that you'll see both biasing methods used. By design, the use self-biasing power tubes is limited to relatively low powered amps, usually 30 watts or less. These amps are generally referred to as "Class A" amps. About the most popular, and most powerful, example of such an amp is the Vox AC30. "Class A" amps are limited in power because of an extreme lack of efficiency inherent in running tubes this way. To get more power out of a set of tubes, it is necessary to operate them more efficiently. This is accomplished by raising the bias voltage and operating the amp in what is known as "Class AB" mode. This higher bias voltage is not possible with self-biasing circuits, so an additional power supply is provided for this purpose. This is the fixed bias I mentioned earlier.

I wouldn't base my decision on what amp to buy on whether it is self-biasing or not. As you said earlier, it really is about TONE. However, I will tell you that I do prefer amps with fixed bias on the power tubes. If you'd like to know why, as well as my opinions on Class A versus AB, solid state versus tube rectifiers, etc., I invite you to check out the two tech articles that are on my web site at www.soldano.com. Happy hunting!
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Once in a blue moon, God reaches down from his lofty perch, points at an infant boy and proclaims, "This one shall have balls carved out of fucking granite."