EL84 current draw help

[soundguruman]

Hmmm, now I'm confused, who should I believe? .

Lowering the heater voltage will not reduce the 60 cycle buzz to an acceptable degree.
Especially in a high gain guitar amp.

We want ALL the noise out, not 15% of it.
That's why DC heaters are used, in everything from Bogners to Mesa Boogies to McIntosh stereos. Even (gag me with an FET) Carvin uses DC heaters in the preamp.
I don't see any of these manufacturers reducing the heater voltage to solve a noise problem. NONE of them do.

If the simple solution was to use 5 Volt heaters on 6.3 volt filaments, then they would all be doing it. That's not a solution. It's a fantasy.

The last commercial amp that lowered the heater voltage to reduce noise was a Radio Craftsman, built in 1954. The idea did not catch on.

But then, there goes the difference between a "tech" and a tech who knows how to play electric guitar. (very loud and impolite)
The "tech" might find the buzz "acceptable" The professional guitar player wants all the noise GONE.
There is an ongoing failure of technicians to understand what a guitar player is really trying to achieve. These techs are not musicians, and they don't understand what the guitar player is facing. They do not have a clue, in fact.

And, you have the same problem with some guy in China designing guitar amps.
He don't play guitar, he's just making an "amp." He don't have a clue what a guitar player wants. He just wants your money.

OK I have built more amps and modified more amps than most of these guys. And for a longer time, also. That's what I learned over the last 38 years of doing it. As a guitar player and technician, at the same time. Take it for what it's worth, but there's something there that can be learned from it.

Most tube data sheets specify an allowable range of filament voltage. This voltage range, without question, satisfies warranty requirements and assures proper performance as related to the filament. We can move voltage outside that range only if the manufacturer approves, or if we properly verify performance. Most important and often overlooked, there are minimum and maximum voltages! While generally not mentioned on amateur radio forums and web pages, excessively low filament or heater voltages can actually be more deleterious than needlessly high filament or heater voltages.
Minimum voltages are especially critical in oxide-cathode tubes. While operation above allowable range deteriorates the very long term emission life to perhaps 60% or so for every 5% above nominal voltage, operation below safe minimum voltages will usually destroy the tube in surprisingly short order. This includes tubes like the 8877/3CX1500A7, 3CX5000A7, and 3CX800A7. I've occasionally seen amplifiers that have been modified to reduce tube filament voltage with repeated short tube life. One amateur amplifier's 8877 was set at 4.2 filament pin volts, and went through a new tube in less than one month of casual amateur operation. The brand new tube, because of low voltage poisoning, had no warranty.
Directly heated tubes (those without heater warm-up time) are more tolerant of low voltage, but not immune. In some cases, a filament management program can extend directly-heated power grid tube, but not always. One private website, and the October 2011 QST Magazine (parroting that private website), make grossly exaggerated claims of increased tube life through reduction of filament voltage to an arbitrarily created value. Unfortunately, not only are life increase promises greatly exaggerated; the target voltage is selected incorrectly, and the article's measurement methods are wrong. The result is SSB bandwidth and tube life can be compromised from excessively low filament voltage.
To comply with tube filament voltage management, the filament must be regulated within +- 3% and a host of other criteria must be met. Here is what Eimac says, in Eimac's own unedited words:

NOTE: If the filament voltage cannot be regulated to within ± 3%, the filament should always be operated at the rated nominal voltage specified on the data sheet. It should be noted that there is a danger to operating the emitter too much on the “cold” temperature side. It may become “poisoned.” A cold filament acts as a getter; that is, it attracts contaminants. When a contaminant becomes attached to the surface of the emitter, the affected area of the emitter is rendered inactive, causing loss of emission.

If we cannot meet all criteria, we should use nominal rated voltage. Nominal rated voltage is given in every tube manufacturer's data sheet, and cannot be arbitrarily rewritten to a new value at whim.
Why a Voltage Range?
Power line voltage varies seasonally and with local time. Most amateur (and many commercial) products, because of size, weight, or cost, cannot use regulated AC filament supplies. Directly heated cathodes also do not work well on DC supplies. A DC supply biases one end of the filament more negative in relationship to grids, and this can unevenly distribute emission current. This is especially problematic in higher voltage filaments with low bias tubes.
Most amateur and many commercial amplifiers or transmitters employ simple step-down filament transformer systems. While filling a cost and space limit, these systems cause filament voltage to vary with power line voltage and transmitter power level changes. Better designs account for filament voltage variation as supply mains (power line) voltage varies, as well as wiring temperature and load power demand variations. Designers should always select the best possible filament voltage to power line voltage relationship, and this relationship must include all causes of filament voltage change over time.
Eimac generally considers +5% or -5% of nominal voltage as an acceptable filament voltage range. Looking at data sheets for the 3-500Z, we see nominal voltage is 5.0 volts RMS, with permissible range between 4.75 and 5.25 volts. The 3CX1200A7 filament is 7.5 volts + - .37 volts, again about 5% plus or minus. Other manufacturers are similar in tolerance. National 811A and Cetron 572B tubes use 6.3 volt filaments, with a specified voltage tolerance of + - 0.3 volts. Once again, tolerance is roughly + - 5% of nominal filament voltage.
If safe filament range is unspecified, +- 5% is a reasonable assumption. It will not be the end of the world if the filament goes outside that range in amateur use, but we should make every reasonable effort to stay within that range. We should always remember that tube life is a combination of many things. Depletion of the filament's ditungsten-carbide layer is one of most frequent problems in broadcast, but one of the least frequent problems in amateur service.

[g1]

SGM: Why are you going on about noise and hum? The statement of yours that I quoted was about tube life:

Reducing the heater voltage shortens the life of the tube quite a bit. That is, anything more than 5% below normal, usually.

So what I am questioning is your claim that lower heater voltages (within reason) reduce tube life.
And we are talking about GUITAR amp tubes. NOT tubes used in amateur radio.
So no need to TAKE someone else's comments about radio tubes and try to pass them off as your own. If you want to use other peoples information, tell us who you are quoting. Or just link to their page.
Here's the link to the information you used (without crediting the author):
Filament Voltage life

[soundguruman]

SGM: Why are you going on about noise and hum? The statement of yours that I quoted was about tube life:
So what I am questioning is your claim that lower heater voltages (within reason) reduce tube life.
And we are talking about GUITAR amp tubes. NOT tubes used in amateur radio.
So no need to TAKE someone else's comments about radio tubes and try to pass them off as your own. If you want to use other peoples information, tell us who you are quoting. Or just link to their page.
Here's the link to the information you used (without crediting the author):
Filament Voltage life

A. Filament Voltage must be maintained in audio tubes OR broadcast. The result of low voltage is the SAME-it shortens the tube life.
Any tube manufacturer or manufacturing engineer in a tube factory would tell you the same. The experienced ones know better...(than you, obviously)
AND I repeat, there IS NO difference.

B. We use broadcast tubes as an example, because broadcasters recognize this problem more than audio guys...and because I AM a broadcast engineer.
1. Because their tubes cost a lot more. 60% reduced life becomes a bigger deal.
2. Because they have more voltage variations at remote transmitter sites, over long power wires...and the voltage drop becomes an obvious problem, to maintain filament voltage.

C. But as I said, there is something to be learned here. You, as a guitar player, don't need to fall into the same pit, and spend unnecessary money for tubes, that have been depleted by low filament voltage. Your tubes last longer with the correct voltage, broadcast OR audio. No Difference.

"Here's a link to the information I used, without crediting the author:"
Pretty much everybody on MEF uses information, and schematics, and everything else, without crediting the author. Who gives a crap? (except you?)
I pasted that in, because I wanted people to learn something. I surmise you don't want to learn, so continue to waddle in the ignorance, you are happier that way, I see.

"Take somebody's comment and pass it off as your own": That problem only exists in your (bent) imagination. You had run out of reasons to berate other people's comments, so you looked for another one. Good try.

Now I hope you can get some anger management counseling...but it won't change the fact that low filaments shorten tube life.