How to ID el84's actual mfg, not who rebranded them

[Orville]

So I finished rolling some preamp tunes in my TA-30 and came back to the Mesa 12ax7's ( JJ's I am fairly sure) I want to look at my power tubes. Quick backstory. I got the amp and had a Mesa certified tech do some Mesa mods that were to help with some of the noisy nature of the amp. Other than the noise ( which were helped quite a bit by the Mesa fixes) I really liked the amp both clean and in Channel 2 ( gain channel) My amp tech stated I had a bad el84 while he had it on the bench - not sure how it was bad as it lit up and I didn't notice anything. He may have tested a short in it or something- I am just learning about tubes! He said I could get a new pair of Mesa tubes or he had a set of 4 Ruby el84s ( he said they were JJ's ) that he could sell me. I asked if they were within the Mesa range, he said el84s were not that picky. The amp came with Mesa green color coded el84's and I was having a hard time finding a duet of those so I said yes to the Ruby's. Something doesn't sound the same as before, and maybe I was rolling preamp tubes to get something back. So here is are my questions, thoughts.

I'd like to be able to look at the power tubes and find distinguishing features so I can say "the Mesa el84 is a ... and the Ruby el84 is a .....
My tech said the Ruby's were JJ's and I'll take his word. But I have read that Mesa el84's could be EH's, or Sovtec. I bought the amp used but I'd guess it was a maybe a 2012? I want to look at the Mesa tube and know who manufactured it for Mesa. I have looked at pics of Sovtec, EH, and JJ online and they all can look similar. My Mesa has a horseshoe chimney and the top mica (?) (the hat on a stem thing) protrudes in front of the open end of the horseshoe. Freaking technical, eh LOL Seem like there is a variation in different mfg's. I see some with the top mica stem off to the side of the chimney. Chinese el84's look different enough to my eyes that I don't think I have those anywhere. So is there a way to look at the structure and get an idea of mfg?
Also just to make sure it is a power tube thang I am hearing, can I run two of the Mesa's with two of the Ruby's? The amp has a 15/30 watt selector. The two middle sockets are for 15 watt. I'd like to run the amp in 15 watt mode and swap the Mesa's with the Ruby's in the middle sockets and see what I hear. I know in 15 watt mode the outer 2 tubes are not active but I don't know if they are still involved in some way that would screw crap up.

Long question, sorry. I am learning as I go and not trying to blow ****e up!!

 

[Gtrjunior]

Re: How to ID el84's actual mfg, not who rebranded them

Generally speaking any power tube swap will require a rebias. Preamp tubes are plug and play.
If your tech removed the Mesa tubes and installed the Ruby tubes he would have rebiased. If you switch back you will want to rebias again.
I’m not 100% familiar with how your amp works ( some amps have a fixed bias and some have cathode bias). But unless I’m mistaken the TA-30 is fixed bias which means the bias needs to be manually adjusted.
If I’m you, and you don’t know how to bias, I’d recommend you leave the tubes alone.

 

[VinceT]

Re: How to ID el84's actual mfg, not who rebranded them

So I finished rolling some preamp tunes in my TA-30 and came back to the Mesa 12ax7's ( JJ's I am fairly sure) I want to look at my power tubes. Quick backstory. I got the amp and had a Mesa certified tech do some Mesa mods that were to help with some of the noisy nature of the amp. Other than the noise ( which were helped quite a bit by the Mesa fixes) I really liked the amp both clean and in Channel 2 ( gain channel) My amp tech stated I had a bad el84 while he had it on the bench - not sure how it was bad as it lit up and I didn't notice anything. He may have tested a short in it or something- I am just learning about tubes! He said I could get a new pair of Mesa tubes or he had a set of 4 Ruby el84s ( he said they were JJ's ) that he could sell me. I asked if they were within the Mesa range, he said el84s were not that picky. The amp came with Mesa green color coded el84's and I was having a hard time finding a duet of those so I said yes to the Ruby's. Something doesn't sound the same as before, and maybe I was rolling preamp tubes to get something back. So here is are my questions, thoughts.

I'd like to be able to look at the power tubes and find distinguishing features so I can say "the Mesa el84 is a ... and the Ruby el84 is a .....
My tech said the Ruby's were JJ's and I'll take his word. But I have read that Mesa el84's could be EH's, or Sovtec. I bought the amp used but I'd guess it was a maybe a 2012? I want to look at the Mesa tube and know who manufactured it for Mesa. I have looked at pics of Sovtec, EH, and JJ online and they all can look similar. My Mesa has a horseshoe chimney and the top mica (?) (the hat on a stem thing) protrudes in front of the open end of the horseshoe. Freaking technical, eh LOL Seem like there is a variation in different mfg's. I see some with the top mica stem off to the side of the chimney. Chinese el84's look different enough to my eyes that I don't think I have those anywhere. So is there a way to look at the structure and get an idea of mfg?
Also just to make sure it is a power tube thang I am hearing, can I run two of the Mesa's with two of the Ruby's? The amp has a 15/30 watt selector. The two middle sockets are for 15 watt. I'd like to run the amp in 15 watt mode and swap the Mesa's with the Ruby's in the middle sockets and see what I hear. I know in 15 watt mode the outer 2 tubes are not active but I don't know if they are still involved in some way that would screw crap up.

Long question, sorry. I am learning as I go and not trying to blow ****e up!!

With Mesa tubes, it’s less about who manufactured than it is about the tolerance. That’s why they only warranty for Mesa replacement tubes. I had the TA15 and, as far as I recall, it’s fixed bias on the assumption that it will use Mesa tubes.

You should check with the your tech whether he re-biased the amp on replacing the tubes.


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[Jacew]

Re: How to ID el84's actual mfg, not who rebranded them

What VinceT said. Whole idea of Mesa having their own brand of tubes is that they're picked so you can switch them without biasing. Manufacturer aside.

Generally tube production is not very accurate, and manufacturer obviously wants to sell all their production, so that's where the rebranding stems from. Knowing who built the tube maybe interesting fact but not necessarily useful.

Some shops also sell tubes labeled so that if you buy same sets from them, you theoretically wouldn't need to rebias.

 

[allbutromeo]

Re: How to ID el84's actual mfg, not who rebranded them

AFIK have a preset bias that is non adjustable. A good idea if you want to try different power tubes in a Mesa is to go through http://www.thetubestore.com when you checkout there is a section where you can tell them what amp you have and they will select tubes that meet Mesa's specs for bias.

 

[jeremy]

Re: How to ID el84's actual mfg, not who rebranded them

almost all mesas are non-adjustable fixed bias. you can stil adjust the bias but it requires changing a resistor. many of the companies are just testing/rebranding companies but jj, new sensor, and shuguang are the big three.

 

[Gtrjunior]

Re: How to ID el84's actual mfg, not who rebranded them

almost all mesas are non-adjustable fixed bias. you can stil adjust the bias but it requires changing a resistor. many of the companies are just testing/rebranding companies but jj, new sensor, and shuguang are the big three.

I think you’ve got that backwards.
Fixed bias means you need to adjust the bias manually, hence setting it to a fixed position.
Cathode bias means the amp is self biasing.


I know....Wikipedia and all but...

https://en.wikipedia.org/wiki/Cathode_bias

 

[Demanic]

Re: How to ID el84's actual mfg, not who rebranded them

almost all mesas are non-adjustable fixed bias. you can stil adjust the bias but it requires changing a resistor. many of the companies are just testing/rebranding companies but jj, new sensor, and shuguang are the big three.

Not to hijack, but this has always puzzled me. Wouldn't it make more sense to make fixed biased amps with some sort of trim pot instead of just a fixed resistor?

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[Darg1911]

Re: How to ID el84's actual mfg, not who rebranded them

I think you’ve got that backwards.
Fixed bias means you need to adjust the bias manually, hence setting it to a fixed position.
Cathode bias means the amp is self biasing.


I know....Wikipedia and all but...

https://en.wikipedia.org/wiki/Cathode_bias

No, I think he has it right.
With fixed bias, the cathode is grounded and a negative voltage is applied to the grid of the power tubes from a dedicated bias circuit. That negative voltage doesn't change. That's why it's called fixed bias. What Jeremy is saying is that there is no bias pot in the MESA amps to adjust that negative voltage. So, you are supposed to use selected, Mesa labeled tubes that will drop in and bias properly in the amp. Otherwise, you need to swap a resistor and/or install a bias pot.

 

[Darg1911]

Re: How to ID el84's actual mfg, not who rebranded them

Not to hijack, but this has always puzzled me. Wouldn't it make more sense to make fixed biased amps with some sort of trim pot instead of just a fixed resistor?

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Yes, for convenience and vesatility sake.

But It makes it easy for non techie amp owners to swap their own tubes as long as they buy the specific tubes for the amp.
It keeps the amp running and sounding like the manufacturer intended (for better or worse), assuming the specific tubes are used.
It sells the companies branded tubes.
It feeds the companies certified techs.

 

[jeremy]

Re: How to ID el84's actual mfg, not who rebranded them

I think you’ve got that backwards.
Fixed bias means you need to adjust the bias manually, hence setting it to a fixed position.
Cathode bias means the amp is self biasing.


I know....Wikipedia and all but...

https://en.wikipedia.org/wiki/Cathode_bias

a typical fender amp is adjustable fixed bias. theres a pot you can use to adjust the fixed bias point, as was mentioned mesas have a resistor, hence non-adjustable fixed bias. cathode bias is "self adjusting" bias but even then some tubes will sound better than others

 

[Orville]

Re: How to ID el84's actual mfg, not who rebranded them

Boogie's do not have a pot for bias, they are factory set. Some people have installed a bias pot. I think back to the 80's Mesa has used the same factory bias point. I can buy a new Mesa tube and it works in my MarkIIb.
I have used tubestore.com. They have been good to me so when I buy tubes I go to them for sure.

Back to my questions LOL !


can I run two of the Mesa's with two of the Ruby's? The amp has a 15/30 watt selector. The two middle sockets are for 15 watt. I'd like to run the amp in 15 watt mode and swap the Mesa's with the Ruby's in the middle sockets and see what I hear.


I'd like to be able to look at the power tubes and find distinguishing features so I can say "the Mesa el84 is a ... and the Ruby el84 is a .....
My tech said the Ruby's were JJ's and I'll take his word. But I have read that Mesa el84's could be EH's, or Sovtec. I bought the amp used but I'd guess it was a maybe a 2012? I want to look at the Mesa tube and know who manufactured it for Mesa. I have looked at pics of Sovtec, EH, and JJ online and they all can look similar. My Mesa has a horseshoe chimney and the top mica (?) (the hat on a stem thing) protrudes in front of the open end of the horseshoe. Freaking technical, eh LOL Seem like there is a variation in different mfg's. I see some with the top mica stem off to the side of the chimney. Chinese el84's look different enough to my eyes that I don't think I have those anywhere. So is there a way to look at the structure and get an idea of mfg?

 

[Darg1911]

Re: How to ID el84's actual mfg, not who rebranded them

Technically, you could have 4 different EL84's from different makers and if they are matched and selected to bias properly within the amp, they would work fine. People have run different brands of the same type of power tubes in guitar amps for a long time though I don't think it's common practice. And, I don't know if it's the best idea, but technically speaking it should be fine.

Post some good photos of the tube and someone will figure out which manufacturers tube it is.

 

[Jacew]

Re: How to ID el84's actual mfg, not who rebranded them

Sovteks and EH's are both New Sensor tubes.

 

[Gtrjunior]

Re: How to ID el84's actual mfg, not who rebranded them

No, I think he has it right.
With fixed bias, the cathode is grounded and a negative voltage is applied to the grid of the power tubes from a dedicated bias circuit. That negative voltage doesn't change. That's why it's called fixed bias. What Jeremy is saying is that there is no bias pot in the MESA amps to adjust that negative voltage. So, you are supposed to use selected, Mesa labeled tubes that will drop in and bias properly in the amp. Otherwise, you need to swap a resistor and/or install a bias pot.

a typical fender amp is adjustable fixed bias. theres a pot you can use to adjust the fixed bias point, as was mentioned mesas have a resistor, hence non-adjustable fixed bias. cathode bias is "self adjusting" bias but even then some tubes will sound better than others

Gotcha...I was unfamiliar with how the Mesa design is. All he tube amps I’ve owned have had bias trim pots.
Plus the terminology is confusing as hell. Lol

 

[Demanic]

Re: How to ID el84's actual mfg, not who rebranded them

^^
In other words, all the amps that you owned we're properly designed without the intent of soaking the consumer for extra fees.

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[jeremy]

Re: How to ID el84's actual mfg, not who rebranded them

it actually gets worse. fender had a bunch of years where they had non-adjustable fixed bias with a balance pot.

 

[Boogie Bill]

Re: How to ID el84's actual mfg, not who rebranded them

I have had good luck with JJ EL84 tubes in my Mesa Maverick 212 and my DC-3 112. I bought them from Bob at Eurotubes. He's close to where I live. Hometown aside, I don't think they are better than the Mesa EL84s.

I believe the Mesa EL84s are Sovtek/New Sensor. But with the six-month warranty on Mesa tubes, it's hard to go wrong with factory tubes.

Personally, I've had terrible luck with Ruby Tubes, and would not buy any of their tubes unless I had to.

The fixed, non-adjustable bias of Mesa's big bottle amps makes perfect sense to me. BTW, I've been using Mesas since about 1994, and I've not spent one dime on biasing, saving me hundreds of dollars. Putting an adjustable bias pot in a Mesa is a waste of money; foolish; and just plain D-U-M-B.

The TA-30 runs in either Class A or Class AB Dyna-Watt...again no biasing needed. My DC-3 is 4xEL84 in Dyna-Watt and sounds like a much bigger amp. The Maverick is Class A, diode or tube rectifier, and covers Vox, Fender and Marshall tones. The TA-30 can do this as well.

Order up a quartet of JJs and some Mesas and see what you like best.

Bill

 

[Demanic]

Re: How to ID el84's actual mfg, not who rebranded them

I have had good luck with JJ EL84 tubes in my Mesa Maverick 212 and my DC-3 112. I bought them from Bob at Eurotubes. He's close to where I live. Hometown aside, I don't think they are better than the Mesa EL84s.

I believe the Mesa EL84s are Sovtek/New Sensor. But with the six-month warranty on Mesa tubes, it's hard to go wrong with factory tubes.

Personally, I've had terrible luck with Ruby Tubes, and would not buy any of their tubes unless I had to.

The fixed, non-adjustable bias of Mesa's big bottle amps makes perfect sense to me. BTW, I've been using Mesas since about 1994, and I've not spent one dime on biasing, saving me hundreds of dollars. Putting an adjustable bias pot in a Mesa is a waste of money; foolish; and just plain D-U-M-B.

The TA-30 runs in either Class A or Class AB Dyna-Watt...again no biasing needed. My DC-3 is 4xEL84 in Dyna-Watt and sounds like a much bigger amp. The Maverick is Class A, diode or tube rectifier, and covers Vox, Fender and Marshall tones. The TA-30 can do this as well.

Order up a quartet of JJs and some Mesas and see what you like best.

Bill

Why is it foolish, dumb and a waste of money?

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[Boogie Bill]

Re: How to ID el84's actual mfg, not who rebranded them

What do you gain from doing it?

Bill