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Tube amp question

I am a novice tube amp owner. I have had my Black Ice Audio Fusion F22 for not quite a year. I want to understand plate voltage and how it impacts tubes or vice versa. I want to roll the tubes to the KT150's which Black Ice has said can be used without issue. The plate voltage of the amp is 500v. In other posts, someone said that KT150's require a minimum of 600v at the plate. Since Black Ice says their amp can use them, does this rating depend on the circuit? I have some basic understanding of electronic circuits and I googled plate voltage but I'm still not clear on what it is exactly. Can someone knowledgeable with tube amps help me understand this? Thanks!

128x128falconquest
falconquest's avatar
falconquest OP
1,108 posts
 

Thanks Atmasphere! this is from an email directly from Jerred at Black Ice...

Here’s a list of the tubes you can use with F22.
EL34, 6CA7, KT77 (Bias is 40mA)
6550, KT88, KT90, KT100, KT120, KT150, KT170 (Bias is 50mA)
 
So this tells me that the amp transformers should be compatible with this tube. With a 500v plate voltage will I be realizing the full potential of this tube? (it appears yes) It is a fully balanced differential push/pull style, class A/B amp. Can someone also explain "plate voltage"? Thanks for all the responses!

 

daveyf's avatar
daveyf
2,857 posts
 

@atmasphere If you place a KT150 on a tube tester, it will not get to spec unless 600 volts is available. As a result, there are few tube testers that can actually test this tube.

atmasphere's avatar
atmasphere
11,740 posts
 

@falconquest Plate voltage is the voltage on the tube from cathode (usually at or near ground) to the plate of the tube. The plate is exactly what it sounds like; it receives electrons that flow from the cathode. The audio signal is imposed by the grid (another element of the tube) over the much larger electron flow from cathode to plate; in this way it can amplify.

@daveyf If it were me I'd be testing a KT150 as a KT88 since our tester is an older Hickok. I would also not be surprised to find that a KT150 might not test properly under those circumstances.

That does not mean that the tube does not work at 400V. It simply points at a limitation in the tester.

falconquest's avatar
falconquest OP
1,108 posts
 

Thanks @atmasphere that clears it up. I have done enough research to understand the parts of the tube so what you say makes sense to me. I appreciate your thoughts. BTW, I have to say I am intrigued by the new class D unit. Thanks again!

daveyf's avatar
daveyf
2,857 posts
 

@atmasphere While I agree with you that a tester that cannot properly test a KT150- shows the limits of the tester, ( BTW, yours- nor any Hickok- I am aware of can test these tubes--and your KT88 spec is no good for them) it also points to the fact that they need more voltage than 400 volts to come to spec, IMHO.

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