EL 84s
- Thread starter bungalowbill
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Yngwiestein
New member
Re: EL 84s
Usually you only need to use matched pairs. I can't think right off hand of an EL84 amp that needs biasing. It's always best to contact the manufacturer because you will get mixed answers from everyone else.
Usually you only need to use matched pairs. I can't think right off hand of an EL84 amp that needs biasing. It's always best to contact the manufacturer because you will get mixed answers from everyone else.
Fresh_Start
New member
Re: EL 84s
Er, the Blues Jr. runs EL-84s, class AB and fixed bias, and I can tell you that adjusting the bias can help the tone a lot. Of course you have to mod it to be able to adjust the bias first.
Many fixed bias EL-84 amps are "less expensive" and manufacturers tend to skip adjustable bias. In addition, a lot of classic EL-84 amps are cathode biased (e.g. Vox) and are therefore self-balancing (no bias adjustment needed).
Chip
Er, the Blues Jr. runs EL-84s, class AB and fixed bias, and I can tell you that adjusting the bias can help the tone a lot. Of course you have to mod it to be able to adjust the bias first.
Many fixed bias EL-84 amps are "less expensive" and manufacturers tend to skip adjustable bias. In addition, a lot of classic EL-84 amps are cathode biased (e.g. Vox) and are therefore self-balancing (no bias adjustment needed).
Chip
Yngwiestein
New member
Re: EL 84s
Like I said "usually" buy matched tubes and "call the manufacturer." I'm not a tech but this is what I usually see in my business.
Like I said "usually" buy matched tubes and "call the manufacturer." I'm not a tech but this is what I usually see in my business.
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Fresh_Start
New member
Re: EL 84s
IME the manufacturer isn't necessarily going to give you a straight answer either. Do you think a Fender tech at the factory is going to tell you "Yeah, the factory bias for a Blues Jr. is way hot. We really should have put a bias pot in there, but the bean counters wouldn't let us" ?
Back to basic rule that if it's fixed bias and there's a bias adjustment, then you ought to check the bias when you replace power tubes. Even if there isn't a bias adjustment, I'd want to check the bias on a new set of power tubes in a fixed-bias amp anyway just to make sure they aren't running really hot (or really cold).
Hope this helps,
Chip
IME the manufacturer isn't necessarily going to give you a straight answer either. Do you think a Fender tech at the factory is going to tell you "Yeah, the factory bias for a Blues Jr. is way hot. We really should have put a bias pot in there, but the bean counters wouldn't let us" ?
Back to basic rule that if it's fixed bias and there's a bias adjustment, then you ought to check the bias when you replace power tubes. Even if there isn't a bias adjustment, I'd want to check the bias on a new set of power tubes in a fixed-bias amp anyway just to make sure they aren't running really hot (or really cold).
Hope this helps,
Chip
James Rock
New member
Re: EL 84s
More likely they will tell you to stick with the awful (in my eyes) rebranded Sovteks that Fender sells.
Bezmotivnik
New member
Re: EL 84s
Why is it so hot? I've never found an answer, and it's still hot, even after several circuit production revisions and guys like Bill Machrone making a big stink about it. Bill has no answer on this either.
It wouldn't have cost one cent more or less to set it up with a colder fixed bias though.
Why is it so hot? I've never found an answer, and it's still hot, even after several circuit production revisions and guys like Bill Machrone making a big stink about it. Bill has no answer on this either.
PUCKBOY99
Irish Flagologist
Re: EL 84s
I've used Groove Tube, Sovtek, Ei, JJ, Mesa Boogie, TAD, NOS Tesla, & not sure how many others.
For straight off the shelf, easy to find & inexpensive, the JJs are worlds apart. This coming from a guy that hates their preamp tubes!
The GTs, Mesa, & Sovteks are all basically the same tube....I think...and depending on the amp & how gritty you wanna get, they aren't "HORRIFIC"...just not as good as the JJs.
I liked the Ei's but someone told me you need to be careful with them...something about the way they're wired can fry a resistor in certain amps. I'm an electronics idiot & couldn't explain it, but I've stayed away from them since then.
The NOS Teslas are SWEET !!!! But of course, a bit pricier. Not Mullard nuts, but pricier than JJs.
Oh and RFT made some that were extremely GREAT....but they're hard to find & pricy too.
:beerchug:
I've used Groove Tube, Sovtek, Ei, JJ, Mesa Boogie, TAD, NOS Tesla, & not sure how many others.
For straight off the shelf, easy to find & inexpensive, the JJs are worlds apart. This coming from a guy that hates their preamp tubes!
The GTs, Mesa, & Sovteks are all basically the same tube....I think...and depending on the amp & how gritty you wanna get, they aren't "HORRIFIC"...just not as good as the JJs.
I liked the Ei's but someone told me you need to be careful with them...something about the way they're wired can fry a resistor in certain amps. I'm an electronics idiot & couldn't explain it, but I've stayed away from them since then.
The NOS Teslas are SWEET !!!! But of course, a bit pricier. Not Mullard nuts, but pricier than JJs.
Oh and RFT made some that were extremely GREAT....but they're hard to find & pricy too.
:beerchug:
Yngwiestein
New member
Re: EL 84s
That's funny because logic would dictate that calling the people who design and manufacture a product is the best way about it. I don't know about Fender because I'm not a Fender dealer but I can tell you all the vendors I have called knew exactly what they were talking about and have been very candid about their advice.
That's funny because logic would dictate that calling the people who design and manufacture a product is the best way about it. I don't know about Fender because I'm not a Fender dealer but I can tell you all the vendors I have called knew exactly what they were talking about and have been very candid about their advice.
Bezmotivnik
New member
Re: EL 84s
Then one day it suddenly stopped.
Now you get customer disservice flunkies who generally dispense misinformation, and only on limited subjects.
With each passing year, corporations more jealously guard any and all proprietary information and do as much as possible to keep consumers in the dark, doing their best to dumb them down and make them better cash-cattle. I've been watching this very closely for many years, and it's really sad.
FMIC used to be very open with information. Real company people openly discussed all sorts of fascinating technical stuff on the FDP.
Then one day it suddenly stopped.
Now you get customer disservice flunkies who generally dispense misinformation, and only on limited subjects.
With each passing year, corporations more jealously guard any and all proprietary information and do as much as possible to keep consumers in the dark, doing their best to dumb them down and make them better cash-cattle. I've been watching this very closely for many years, and it's really sad.
J.LaGrassa
New member
Re: EL 84s
I've tried JJ EL84 and TAD EL84 STR in my VHT Super 30, the TAD EL84 sound a lot clearer and bigger bass and stays very tight. The TAD tubes cost a little bit more but I think they are worth it, the JJ's are very good but just not in my VHT.
I've tried JJ EL84 and TAD EL84 STR in my VHT Super 30, the TAD EL84 sound a lot clearer and bigger bass and stays very tight. The TAD tubes cost a little bit more but I think they are worth it, the JJ's are very good but just not in my VHT.
Myles
New member
Re: EL 84s
The best EL84 currently produced from my own personal experience is the JJ EL84S. Tone, articulation, construction, reliability and life exceed all the other current production offerings.
If you are talking NOS though, there are a number of great ones.
The best EL84 currently produced from my own personal experience is the JJ EL84S. Tone, articulation, construction, reliability and life exceed all the other current production offerings.
If you are talking NOS though, there are a number of great ones.
bungalowbill
Luckybastidologist
Re: EL 84s
The JJ's worked out great! Very fat and a lot cleaner. I also put one of their ecc83s in V1 and that got rid of a lot of the edgy high end.
I don't think their pre's would be good in a dark sounding amp, but they work great in a V-32.
The JJ's worked out great! Very fat and a lot cleaner. I also put one of their ecc83s in V1 and that got rid of a lot of the edgy high end.
I don't think their pre's would be good in a dark sounding amp, but they work great in a V-32.
Myles
New member
Re: EL 84s
Chip,
The Eis were great in a lot of amps tonally. In a Dr. Z Mazerati which has a split bias ... the left two tubes with a seperate bias supply than the right two tubes (not inner and outer as most grid biased amps with four tubes) ... I liked JJs for one pair and Eis for the other pair for some clients.
But ... the caviat .... the Eis tended to be very unreliable to physical shock such as road travel on tour. If you use these on the road you will need to carry spares as they can fail or become physically microphonic with little or no warning.
Chip,
The Eis were great in a lot of amps tonally. In a Dr. Z Mazerati which has a split bias ... the left two tubes with a seperate bias supply than the right two tubes (not inner and outer as most grid biased amps with four tubes) ... I liked JJs for one pair and Eis for the other pair for some clients.
But ... the caviat .... the Eis tended to be very unreliable to physical shock such as road travel on tour. If you use these on the road you will need to carry spares as they can fail or become physically microphonic with little or no warning.
Myles
New member
Re: EL 84s
A few things to keep in mind here.
Mesa used to use the Sovtek EL84 which was the darkest and most constricted sounding EL84 but they were cheap and reliable. If you like the tone of your Mesa with those and have not tried something else you may want to try something else as you may like your amp even more after the change.
Second ... matching..... Mesa octal tubes (6L6, EL34, 6V6) come with six color codes ..... red, orange, green, gray, blue, white. These codes are on the base of the tube. Red by the way is the coldest tube and white is the hottest within that range. BUT ... you will not see any sort of match or color code on their EL84 tubes. Perhaps their logic is that cathode biased amps are self biasing and they feel the tubes do not need to be matched so these are not matched. If they work and do not make noise individually they pass and are boxed.
The problem here is that cathode biased amps have a bias network that expects as per design a tube that is close to the design spec of the tube. If a tube is weak it runs cold which sounds grainy and does not allow the amp to produce full power. If the tube is overly strong compared to expected design spec it sounds harsh, runs too hot and has short life.
The second problem is that when the tubes are more than 20% off on match you will get background hum in the output stage at all levels and loose sustain, articulation and definition as well.
So ... if you had good luck with the Mesa EL84 offerings it was just that ... luck. It had nothing to do with matching.
On the other hand, the matching Mesa does on their octal tubes is very good. Due to the fixed bias design of their amps they need to only offer tubes in a narrow range which is a range centered around actual design spec. If you break down the color code and convert it to the GT rating system is looks like this:
Red = GT 4
Orange = GT 4
Green = GT 5
Gray = GT5
Blue = GT 6
White = GT 6
Mesa grid biased amps are generally overbiased and run cold so I always try to find blues and whites for my Mesa folks that want to use Mesa tubes. If you check the bias on Mesa amps with reds or oranges you may discover that the idle dissapation is as low as 28-30% where 50-60% is expected. Move to a blue or white and you will be closer to where the amp should be running.
A few things to keep in mind here.
Mesa used to use the Sovtek EL84 which was the darkest and most constricted sounding EL84 but they were cheap and reliable. If you like the tone of your Mesa with those and have not tried something else you may want to try something else as you may like your amp even more after the change.
Second ... matching..... Mesa octal tubes (6L6, EL34, 6V6) come with six color codes ..... red, orange, green, gray, blue, white. These codes are on the base of the tube. Red by the way is the coldest tube and white is the hottest within that range. BUT ... you will not see any sort of match or color code on their EL84 tubes. Perhaps their logic is that cathode biased amps are self biasing and they feel the tubes do not need to be matched so these are not matched. If they work and do not make noise individually they pass and are boxed.
The problem here is that cathode biased amps have a bias network that expects as per design a tube that is close to the design spec of the tube. If a tube is weak it runs cold which sounds grainy and does not allow the amp to produce full power. If the tube is overly strong compared to expected design spec it sounds harsh, runs too hot and has short life.
The second problem is that when the tubes are more than 20% off on match you will get background hum in the output stage at all levels and loose sustain, articulation and definition as well.
So ... if you had good luck with the Mesa EL84 offerings it was just that ... luck. It had nothing to do with matching.
On the other hand, the matching Mesa does on their octal tubes is very good. Due to the fixed bias design of their amps they need to only offer tubes in a narrow range which is a range centered around actual design spec. If you break down the color code and convert it to the GT rating system is looks like this:
Red = GT 4
Orange = GT 4
Green = GT 5
Gray = GT5
Blue = GT 6
White = GT 6
Mesa grid biased amps are generally overbiased and run cold so I always try to find blues and whites for my Mesa folks that want to use Mesa tubes. If you check the bias on Mesa amps with reds or oranges you may discover that the idle dissapation is as low as 28-30% where 50-60% is expected. Move to a blue or white and you will be closer to where the amp should be running.
Myles
New member
Re: EL 84s
A few points to try to help here ....
The JJ is not Russian it is what was Czech, now Slovakia.
The stock tube in Z EL84 amps were the EL84S (JJ) in a #5-6 rating.
If you have GT stuff that is going south contact Mike Fineburg at Kaman which took over GT and try to get them replaced under warranty. When I was at GT we would always replace stuff, no questions asked, in any new Z amp.
A few points to try to help here ....
The JJ is not Russian it is what was Czech, now Slovakia.
The stock tube in Z EL84 amps were the EL84S (JJ) in a #5-6 rating.
If you have GT stuff that is going south contact Mike Fineburg at Kaman which took over GT and try to get them replaced under warranty. When I was at GT we would always replace stuff, no questions asked, in any new Z amp.
Myles
New member
Re: EL 84s
Get rid of the Sovteks .... and new EL84s are plug and play ... no adjustment necessary.
There are a lot of great vendors but two I use all the time ... and just tell them you want "mid range" design spec tubes are ....
www.dougstubes.com
www.kcanostubes.com
There are many other great vendors, the two above are just ones that I have years of personal experience with and know how they test things.
As an example ... from Doug Preston, a matched quad of EL84's is $44. (When I have amps that need a duet I generally buy a quad so I have a backup matched pair). A duet from Doug is $22. Compared to the EL84S from GT the GT cost is $100 for a quad and $50 for a duet so even with a discount the GT version is about twice the price.
The difference? There is one difference ..... one tube has a GT logo on it and the other has a JJ logo on it.
From Antique Electric Supply - www.tubesandmore.com a quad is $43 as a side note but if you go there ask for Brandon or Steve or find somebody there that knows me personally and has the documentation I supplied to them so they get you a set of tubes to proper spec.
All three of the above folks are great but if you want to develop a long term personal relationship with your tube folks and deal with the same person all the time then Doug and KCA are my favorites. Mike at KCA is also one heck of an amp tech as a side note.
Get rid of the Sovteks .... and new EL84s are plug and play ... no adjustment necessary.
There are a lot of great vendors but two I use all the time ... and just tell them you want "mid range" design spec tubes are ....
www.dougstubes.com
www.kcanostubes.com
There are many other great vendors, the two above are just ones that I have years of personal experience with and know how they test things.
As an example ... from Doug Preston, a matched quad of EL84's is $44. (When I have amps that need a duet I generally buy a quad so I have a backup matched pair). A duet from Doug is $22. Compared to the EL84S from GT the GT cost is $100 for a quad and $50 for a duet so even with a discount the GT version is about twice the price.
The difference? There is one difference ..... one tube has a GT logo on it and the other has a JJ logo on it.
From Antique Electric Supply - www.tubesandmore.com a quad is $43 as a side note but if you go there ask for Brandon or Steve or find somebody there that knows me personally and has the documentation I supplied to them so they get you a set of tubes to proper spec.
All three of the above folks are great but if you want to develop a long term personal relationship with your tube folks and deal with the same person all the time then Doug and KCA are my favorites. Mike at KCA is also one heck of an amp tech as a side note.
Myles
New member
Re: EL 84s
Superb point here:
You'll get more of a change in sound from your preamp tubes than you will from the power tubes
You are right on the money.
In many amps the differences in output tubes actually do very little. What you are hearing in many cases is the phase inverter breaking down and that signal being passed to the output tubes. Most 12AX7s these days have plate current as low as 1/2 of expected output and your output section will distort faster in this case or be indistinct of flubby. If you have two tubes that are close to spec, a long plate and short plate you will probably hear a difference as well as the output section is driven harder.
In many cases tube makers would rather have you buy a new output set of tubes which are more pricy (and in many cases will require a rebias in grid biased amps) than a plug and play cheaper 12AX7 or other tube in the phase inverter position which has much more effect.
Chad Weaver (Brad Paisley) has a selection of phase inverters for Brad's amps that are all documented as to their plate current output, transconductance, plate resistance and actual true gain in circuit (transconductance is a design spec test and not always stated as in an actual amp circuit so both factors are nice to know). Depending on need or venue Chad can change the PI for a given venue or session.
But .... the bottom line here is you are right on the money with your statement
Superb point here:
You'll get more of a change in sound from your preamp tubes than you will from the power tubes
You are right on the money.
In many amps the differences in output tubes actually do very little. What you are hearing in many cases is the phase inverter breaking down and that signal being passed to the output tubes. Most 12AX7s these days have plate current as low as 1/2 of expected output and your output section will distort faster in this case or be indistinct of flubby. If you have two tubes that are close to spec, a long plate and short plate you will probably hear a difference as well as the output section is driven harder.
In many cases tube makers would rather have you buy a new output set of tubes which are more pricy (and in many cases will require a rebias in grid biased amps) than a plug and play cheaper 12AX7 or other tube in the phase inverter position which has much more effect.
Chad Weaver (Brad Paisley) has a selection of phase inverters for Brad's amps that are all documented as to their plate current output, transconductance, plate resistance and actual true gain in circuit (transconductance is a design spec test and not always stated as in an actual amp circuit so both factors are nice to know). Depending on need or venue Chad can change the PI for a given venue or session.
But .... the bottom line here is you are right on the money with your statement
Myles
New member
Re: EL 84s
Actually I was not a consultant for GT I was an employee that did their tube test, development, ran the SAG (special applications group), was their tech support and wrote a number of pieces in The Tube Amp Book so I was there quite a lot and was there from May 2002 until August 15, 2008 when GT was sold to Fender.
Part of my deal with them was that I would only work 20 hours a week and would be allowed to be independent so when I felt other folks did something in a better way I could be free to recommend a product that might have come from the competition. This generally worked out fairly well but was the source of many problems now and then An example of one of these was an occasion when I did some testing for Tom McNeil at Ruby Tubes. They had an EL34 that was an exceptional tube. I did a big writeup test report and Tom asked me if he could publish some aspects of the report. Since I put most of my test stuff on my website and feel that anything I put on my website is public domain once it is put on the net I said "sure". The report in it's complete form was put into the front pages of the Ruby Tubes catalogue that was distributed at NAMM that year. Ruby's booth was within sight of GT's booth less than 50 feet away. Many folks showed the catalog to Aspen Pittman I guess. It did not go over well. When people asked me directly if I had something bad to say about the tube I did have one thing to say .... "Ruby has it and GT does not". After that comment got around GT started to buy the EL34BSTR from Ruby and sell it as their EL34C but a bit down the road GT switched to a Shuguang generic EL34 as it was cheaper.
So the bottom line reply to what you wrote ... consultant no. Captive employee yes.
But today I am a consultant to a number of folks and have no intension of being a captive employee again for anybody.
Actually I was not a consultant for GT I was an employee that did their tube test, development, ran the SAG (special applications group), was their tech support and wrote a number of pieces in The Tube Amp Book so I was there quite a lot and was there from May 2002 until August 15, 2008 when GT was sold to Fender.
Part of my deal with them was that I would only work 20 hours a week and would be allowed to be independent so when I felt other folks did something in a better way I could be free to recommend a product that might have come from the competition. This generally worked out fairly well but was the source of many problems now and then
An example of one of these was an occasion when I did some testing for Tom McNeil at Ruby Tubes. They had an EL34 that was an exceptional tube. I did a big writeup test report and Tom asked me if he could publish some aspects of the report. Since I put most of my test stuff on my website and feel that anything I put on my website is public domain once it is put on the net I said "sure". The report in it's complete form was put into the front pages of the Ruby Tubes catalogue that was distributed at NAMM that year. Ruby's booth was within sight of GT's booth less than 50 feet away. Many folks showed the catalog to Aspen Pittman I guess. It did not go over well. When people asked me directly if I had something bad to say about the tube I did have one thing to say .... "Ruby has it and GT does not". After that comment got around GT started to buy the EL34BSTR from Ruby and sell it as their EL34C but a bit down the road GT switched to a Shuguang generic EL34 as it was cheaper.So the bottom line reply to what you wrote ... consultant no. Captive employee yes.
But today I am a consultant to a number of folks and have no intension of being a captive employee again for anybody.
Myles
New member
Re: EL 84s
You are on the money here .... the Blues Jr is one of the few grid biased EL84 amps and if you are outside the range they don't work well. The reason Fender went the EL84 route on this amp was price .... a duet of EL84 tubes is less than a duet of 6V6 tubes.
You are on the money here .... the Blues Jr is one of the few grid biased EL84 amps and if you are outside the range they don't work well. The reason Fender went the EL84 route on this amp was price .... a duet of EL84 tubes is less than a duet of 6V6 tubes.
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