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Old 21st March 2014, 07:04 PM   #1
KP11520 is offline KP11520  United States
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Default EL84 "IP" questions

Hey Tube / Valve Gang,

I need some guidance about what "IP" means for an EL84.

I have a Laney Lionheart l5t-112 5 watt guitar amp. It uses only one EL84. (BTW, this is more a tube question than a guitar amp question and why I posted this here)

So I have read many great reviews about the Genalex Gold Lion EL84's. And a few about how they just blow when installed in a hot amp. But the description sounds like what I'm looking for. More clean headroom.

So I received one today in the mail and the box is marked with: "IP=28"

So I went searching on the Internet for what this means. Nothing definitive that matches the situation that I can relate to. However, I did read that 28 ma is where the tube/valve goes from useable to good and the "good" range is from 28 to 48.

So, is this most likely a tube that I should return, or is this a different value that means something else?

Please advise! Never bought a tube for an amp before. I'd like to do it right!

Thanks Fellas!
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Old 21st March 2014, 07:57 PM   #2
DF96 is offline DF96  England
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"IP" doesn't mean anything. "Ip" could mean plate current. Modern valves vary greatly in their characteristics. Somewhat low emission does not necessarily mean low performance or short life, as it would depend on the exact circuit requirement and how stable the emission is.
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Old 21st March 2014, 11:06 PM   #3
KP11520 is offline KP11520  United States
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Thank you!

Looking closer at the sticker he wrote this on, it is "Ip".

Plate current on EL84's is measured in milliamps? And if that number is 28, I guess the tube is straddling useable and good.

In my twisted little brain, he had to put that number measurement on it for a reason. I offered less than he was asking. Maybe these "on the edge" tubes are for those who do that.

So, how twisted is my thinking? LOL
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Old 22nd March 2014, 03:29 AM   #4
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It annoys me when sellers quote a test figure with no supporting info.
Ip=28mA, yes, but at what bias level, plate voltage, screen voltage, even heater voltage.
Without those extra parameters, an Ip figure is almost meaningless.
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Old 22nd March 2014, 03:57 AM   #5
KP11520 is offline KP11520  United States
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You know.... Thank you! I'm going to send a PM through eBay and ask him what are all the unknowns.

I guess he's using a tester. Which? Who knows. Maybe a $99 special that never experienced the word... Calibration. But how is a customer to really know what they got unless they spent hundreds of dollars for something used and calibrated. (up to thousands for new or used)

Lots of potential victims.... I mean customers out there. LOL

Funny, when I Google "How to test an EL84" or "EL84 Test Values" or several other phrases, NOTHING even comes close to explaining what are the desired numbers or what are the required tests to determine where a tube sits in the big picture of its peers. I guess people who are more intimate with tube theory, design and repair, know, but for ignorant peeps like me, even knowing where to look to understand this is evasive. I didn't get the memo. LOL

Thanks for the torch under my butt to go to the source and drill down on this!

Quote:
Originally Posted by rotaspec View Post
It annoys me when sellers quote a test figure with no supporting info.
Ip=28mA, yes, but at what bias level, plate voltage, screen voltage, even heater voltage.
Without those extra parameters, an Ip figure is almost meaningless.
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Old 22nd March 2014, 04:27 AM   #6
chrish is offline chrish  Australia
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I suspect it is just a figure measured at some specific operating point for the purpose of matching tubes. If you had asked for a matched pair, you would receive two who's 'Ip' number would be close to the same value. Since you have a single, I would pay no notice of it at all.
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Old 22nd March 2014, 03:17 PM   #7
KP11520 is offline KP11520  United States
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Si I did PM the eBay seller and ask for all the other numbers involved in the testing so I can determine where, on a scale of 1 to 10 this EL84 sits.

He said it was a 3 and that means early breakup on my guitar amp. I asked if I could swap it for something much closer to 10 because I read the Gold Lion offers high clean headroom and stays articulate in guitar amps. I want the clean headrom rather than early breakup. He said to try it and if I don't like it, he'll see if he can find one better suited.

NOT a straight answer. Probably worth spending 50% more at a reseller that caters to guitarists and cares about their reputation and supports their test findings with facts and real numbers.

Thanks for the support fellas!

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Originally Posted by chrish View Post
I suspect it is just a figure measured at some specific operating point for the purpose of matching tubes. If you had asked for a matched pair, you would receive two who's 'Ip' number would be close to the same value. Since you have a single, I would pay no notice of it at all.
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