EL 84s

[Myles]

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

The Blue Jr. works best with the Fender "white" tubes which are GT 4-7 rating. These are mid range tubes (think tubes that are close to design spec of a given tube) and are the proper range. The "blue" tubes (1-3) run cold and the "red" will run too hot. Fender uses all three colors as the way their deal may have worked with GT may have required them to buy some of all the color codes or something like that, I don't know.

In any case, if you go to a good tube vendor that tests things properly and ask for a mid range tube or a tube that meets design spec ( RCA / Mullard spec is .... at 250 plate volts, 250 screen volts, -7.3 volt bias the plate current should be 48mA) you will be great.

For folks that supply tubes and use a Maxi-Matcher that uses 325 volts and a -12 volt bias just stay in the middle of their silk screened chart on the tester.

 

[Myles]

Re: EL 84s

More likely they will tell you to stick with the awful (in my eyes) rebranded Sovteks that Fender sells.

Fender generally used the GT-EL84R which are indeed the Sovtek. That is the darkest most constipated EL84 around in my personal experience. A great upgrade to these amps is toss those or keep as spares and put in anything else.

If the amp has 12AX7R tubes in the front end try replacing those as well with almost anything else. 12AX7EH, 12AX7 Tung Sol reissue, 12AX7C all work great and are not expensive. I like the 12AX7LPS (Sovtek) or the JJ 803S in the phase inverter in these amps but that is my own personal taste for long plates in a PI position in some amps.

 

[Myles]

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.

Be sure when you compare two different tubes they both test close to each other. In many cases, most actually ... a person will pick a tube that is at spec over a tube 30-50% below spec which is very very very commmon today.

 

[J.LaGrassa]

Re: EL 84s

Be sure when you compare two different tubes they both test close to each other. In many cases, most actually ... a person will pick a tube that is at spec over a tube 30-50% below spec which is very very very commmon today.

cant say for sure how close in spec they were the JJ's were selected from Bob at Eurotubes and the TAD from Dougs tubes, both dealers knew they were for my VHT!

My amp sounds very bland with all JJ tubes installed its funny because I always used JJ tubes when I had fender amps and they were great, VHT sounds best with Chinese Pre's (Penta Labs) and TAD Power tubes!

 

[Myles]

Re: EL 84s

cant say for sure how close in spec they were the JJ's were selected from Bob at Eurotubes and the TAD from Dougs tubes, both dealers knew they were for my VHT!

My amp sounds very bland with all JJ tubes installed its funny because I always used JJ tubes when I had fender amps and they were great, VHT sounds best with Chinese Pre's (Penta Labs) and TAD Power tubes!

Well .... in the case of preamp tubes there are wide variances that folks call "good tubes". If you are close to SoCal sometime and want me to test and trace some of the stuff you have I would be happy to do so. Actually ... that same deal goes to everybody that might read this. You have to be here in person as I do not ship things back and forth.

 

[tone4days]

Re: EL 84s

myles

thanks so much for your contributions to this thread and our little forum here ... please stick around because it is clear you are in the 'national treasure' league of guys who know tubes
cheers
t4d

 

[Myles]

Re: EL 84s

myles

thanks so much for your contributions to this thread and our little forum here ... please stick around because it is clear you are in the 'national treasure' league of guys who know tubes
cheers
t4d

I will stick around and thanks for the compliment.

This is a very cool group of folks that all seem to have a basic agenda of helping each other and that is something that can be quite rare on many forums.

 

[J.LaGrassa]

Re: EL 84s

Well .... in the case of preamp tubes there are wide variances that folks call "good tubes". If you are close to SoCal sometime and want me to test and trace some of the stuff you have I would be happy to do so. Actually ... that same deal goes to everybody that might read this. You have to be here in person as I do not ship things back and forth.

Wish I were in Cali Myles I would love to have you work your magic but I'm so far away in Taxachusetts

 

[Myles]

Re: EL 84s

Wish I were in Cali Myles I would love to have you work your magic but I'm so far away in Taxachusetts

Talking about taxes ... they want to raise the sales tax in CA and in L.A. the proposed new rate is 10.25%. Is that about as bad as it gets or what?

 

[wanmei1]

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.

Myles,
Are you aware that EI el84's and indeed a lot of NOS tubes are not compatible with some amps such as recently manufactured Vox AC30 and Laney VC 30's due to internal wiring differences in the pin used for ground ?

 

[Robert S.]

Re: EL 84s

Welcome aboard Myles!

This is a great group of guys and you are a welcome addition.

 

[JumpMarine]

Re: EL 84s

Myles,
Are you aware that EI el84's and indeed a lot of NOS tubes are not compatible with some amps such as recently manufactured Vox AC30 and Laney VC 30's due to internal wiring differences in the pin used for ground ?

Do you know who this guy is? He know's.....

 

[Fresh_Start]

Re: EL 84s

Myles,
Are you aware that EI el84's and indeed a lot of NOS tubes are not compatible with some amps such as recently manufactured Vox AC30 and Laney VC 30's due to internal wiring differences in the pin used for ground ?

Umm, if there's a problem with those amps, it's the fault of the amps not the EL-84 tubes.

Do you know what the actual problem is with these amps and which tube brands/manufacturers do make compatible "EL-84s"?

EL-84 pinout is:
2 - control grid
3 - cathode and suppressor grid
7 - plate
9 - screen grid
4 & 5 - heaters
1, 6 & 8 are internal connections

Maybe some new "EL-84" tubes aren't really EL-84s. Just a guess - the AC-30 may use one or more of the internal connection pins to mount a component because some new not-really-EL84s don't use a pin for one or more of those connections.

It wouldn't be the first time this happened. Sovtek "5Y3GT" rectifier tubes don't meet specs for that tube at all and the voltage drop is 20-30 volts less than it should be. There's a mechanical difference between how the cathode and heater are connected (or not connected).

Chip

 

[Myles]

Re: EL 84s

Myles,
Are you aware that EI el84's and indeed a lot of NOS tubes are not compatible with some amps such as recently manufactured Vox AC30 and Laney VC 30's due to internal wiring differences in the pin used for ground ?

Yes, that can be an issue at times. Another issue in amps that have PCB mounted output tube sockets with a hole in the chassis where the tube has to pass through the hole to hit the socket ... the hole is based on spec bottle diameter which used to be consistent in the past but is not consistent these days at times. So ... you cannot even get the tube installed in the amp in the first place.

That 0.875 outer diameter can get to 0.90 and even larger.

 

[wanmei1]

Re: EL 84s

Yes, that can be an issue at times. Another issue in amps that have PCB mounted output tube sockets with a hole in the chassis where the tube has to pass through the hole to hit the socket ...

I noted that you said in another post that you thought they were a good sounding tube apart from the reliability issues.

I think it could be advisable to point out that the tube is actually unsuitable for a few currently manufactured amplifiers and should not be used unless modifications to the amps wiring or the tube itself is made.

I wonder how many people have bought and installed Ei's only to have the fuses go or worse.

The manufacturer makes no mention of this also.

It would seem to me that for those that wish to use these tubes and don't want to modify their amp by having the sockets wiring altered, the thing to do would be to snip off pin number 1 of each tube with a pair of cutters.

 

[Fresh_Start]

Re: EL 84s

I think it could be advisable to point out that the tube is actually unsuitable for a few currently manufactured amplifiers and should not be used unless modifications to the amps wiring or the tube itself is made.

Please let me know what the actual problem is with these amps and which tube brands/manufacturers do make compatible "EL-84s".

Sounds like those amps you mentioned use pin #1 for something they shouldn't, but I'd really appreciate clarification. Especially since you said the warning applies to NOS EL-84s as well as Ei EL-84s.

I'm not disagreeing with you - just want to learn.

Chip

 

[Myles]

Re: EL 84s

I noted that you said in another post that you thought they were a good sounding tube apart from the reliability issues.

I think it could be advisable to point out that the tube is actually unsuitable for a few currently manufactured amplifiers and should not be used unless modifications to the amps wiring or the tube itself is made.

I wonder how many people have bought and installed Ei's only to have the fuses go or worse.

The manufacturer makes no mention of this also.

It would seem to me that for those that wish to use these tubes and don't want to modify their amp by having the sockets wiring altered, the thing to do would be to snip off pin number 1 of each tube with a pair of cutters.

If you are talking Ei's ... yes, they can sound great but the reliability factor is terrible.

 

[wanmei1]

Re: EL 84s

Please let me know what the actual problem is with these amps and which tube brands/manufacturers do make compatible "EL-84s".

Sounds like those amps you mentioned use pin #1 for something they shouldn't, but I'd really appreciate clarification. Especially since you said the warning applies to NOS EL-84s as well as Ei EL-84s.

I'm not disagreeing with you - just want to learn.

Chip

This is really a question for Myles to answer as he is the expert.

Myles will have a list of Ei tube incompatible amps , and a list of NOS tubes that won't work in these amps.
Here's all I know.......

I threw in a set of EI el84's into my ( at the time ) Laney VC30 and
Bang !......
Instant fuse disintegration.
During the course of my enquiries I contacted Laney and they said they new nothing about incompatibilty with any tubes.
I contacted a few tube places and they didn't know anything about this either.

The wiring of tube sockets on some modern amps has a different wiring configuration to most amps making them incompatible with a lot of NOS tubes and also incompatible with Ei El84 tubes as well.
Both NOS and Ei El84's are internally wired the same way, which is to say different to most modern manufactured tubes.

In NOS and Ei tubes, Pin1 and Pin 2 are tied together internally.

There may be other currently manufactured tubes that are incompatible as well, I dont think so however Myles will know if there are any others.

Some some current production versions of the Vox AC30,
The Laney VC 30, Lexicon signature 284 and Fender Vibro king are not suitable for NOS or Ei tubes.
Check with the amp manufacturers but I think most will tell you they've never heard of such a thing at least they hadn't a couple of years ago.

There are others too I think, but for a better explanation of the above and a full list of tubes and amps etc., you will have to ask Myles.

 

[wanmei1]

Re: EL 84s

If you are talking Ei's ... yes, they can sound great but the reliability factor is terrible.

Not to mention the atrocious signal to noise ratio of a lot of these tubes.

One of the many importers for these tubes in the US are selling Ei's in a different color box to the normal Ei's and have been burnt in for 24 hours and then tested for s/n and general specs and those tubes that pass are then treated to having the pins gold plated.
These tubes are sold at a premium price over the non tested tubes with non plated pins and may,....MAY....go some way to addressing the poor quality control of the factory.
I say may as I haven't tried em'.....how about you ?

Can you address my post below re a list of amps and tubes that are incompatible.

 

[Myles]

Re: EL 84s

There is really no list of what is wired in what way. It can even change from run to run from the same tube maker to cut cost.

Basically ... if there ever is a problem you should contact the tube seller and have them complain to the vendor and cover the cost of repairs if the vendor does not use the design pin spec as shown in the first post I did here. If the are not design spec then there should be a warning or data sheet on the box or supplied with the tube.

The 9cv drawing about is how the tube should always be wired.