Orange Amps Forum

Got a pair of matched tung sol el 84s coming next week, can i drop em in without need for rebiasing ?

Since it is based on the terror platform, and < 50 Orange watts, I would say YES! That said, the manual does talk about "getting a qualified technician to bias". So I have no idea. What a pointless post from me

REDEMPTION!

viewtopic.php?t=55438

Let us know how you like the new valves.

What valves came in it originally? I take the valves are not that old?

yeah ive always dug tung sol tubes and the jj's my rocker terror came with will make good spares.

Bump. If anyone has a definite answer to this question I would really appreciate it! The best is have been able to find so far are educated guesses, but not a definitive answer yet. Thanks!

Your amp is cathode biased. Pop those Tungsols in and rock on.

Thanks!

Also, I contacted orange directly, and they confirmed the following: Rocker 15 Terror is a class A amp, and biasing is not necessary when changing the power tubes.

dhalaney wrote: ↑

Tue Apr 24, 2018 10:17 pm

Thanks!

Also, I contacted orange directly, and they confirmed the following: Rocker 15 Terror is a class A amp, and biasing is not necessary when changing the power tubes.

Operating class is independent of biasing method. The amp is cathode biased, therefore the tubes will *usually* drop in and operate without worry.

It is still prudent to keep an eye on them to make sure they are not red plating. That’s a quick and crude method of verification, but likely all you will have (or need) to ensure there aren’t any problems.

And Orange talks the “Class A” marketing game just like everyone else. It’s unlikely the amp is true Class A. But that’s a different discussion! Haha.

fiveightandten wrote: ↑

Tue Apr 24, 2018 10:24 pm

It is still prudent to keep an eye on them to make sure they are not red plating.

Thanks for the info! How do I tell if the tubes are red plating? Like, will they literally be glowing red? And if they do, I should go get the amp biased, even though it is cathode biased? New to the world of tube amps, and thirsty for knowledge, so I really appreciate anything you can teach me

dhalaney wrote: ↑

Tue Apr 24, 2018 10:35 pm

Thanks for the info! How do I tell if the tubes are red plating? Like, will they literally be glowing red? And if they do, I should go get the amp biased, even though it is cathode biased? New to the world of tube amps, and thirsty for knowledge, so I really appreciate anything you can teach me

Every tube set draws a different amount of current. A cathode biased amp will adjust itself over a certain range, but tube sets that draw a lot could potentially run too hot in the amp.

You’re correct, the plates (the big vertical metal pieces) will literally glow cherry red when a tube is running to hot (at that point, it’s way too hot). I’ve had this happen with some tubes sets in my Vox AC-30. This isn’t the small metal filaments that glow whenever the amp is on, it would be the big metal pieces glowing red hot. If this happens, I’d return them and get a new set. You can request lower draw tubes as the replacements. This, IMO, is better than altering the cathode resistor values in the amp (which is how you’d have to adjust the bias).

This is why good tube suppliers will ask you what amp the tubes are going in. They will select a set that will run within spec in the amp. Many EL84 amps are cathode biased.

In all likelihood, whatever tubes you use will be ok. But the misconception that every set runs the same in the amp isn’t true. I’ve had plenty of sets that ran way too hot in my Vox, and a few that were too hot in my Orange AD30. It does happen, so although it’s uncommon, IMO it’s prudent to understand that you’re dealing with a range, and at least doing a visual check to make sure they’re not red plating. I prefer to measure the bias. But not everyone has the tools or experience with that.

Hope that helps.

dhalaney wrote: ↑

Tue Apr 24, 2018 10:35 pm

Hope that helps.

It helps a lot! Thanks fiveightandten!