Are you kidding me!? Really!?

[MWJB]

Class AB guitar amp is this?

[Wilder Amplification]

Class AB guitar amp is this?

Yes.

[MWJB]

Come on then, put me out of my misery...:-)

[Jazz P Bass]

What are the limiting factors to a vacuum tubes current rating?
There are the mechanical aspects, heat dissipation & such.
And then there are the electrical aspects.
The cathode, when heated, "boils off" electrons creating a space charge.
When a steadily increasing positive voltage is applied to the plate, the voltage field reaches into the space charge & pulls electrons to it.
Think diode.
Wallah. Measurable current.
The negative grid voltage is what controls how far into the space charge the positive field can reach.
The amount of electrons available from the cathode, at a constant temperature, does not change even if the plate voltage is changed.
So maybe JJ is using a smaller cathode?

[ivey]

No.

They are using a different material for the plate.

Maybe a low grade Monel metal. Good for about 3300 deg. f
Tungsten (element #74) is good to 4500 deg. f or greater.
Heating elements in space heaters is make of nickel/copper (Monel)
and it comes in different grades. Submarines in the US use Monel 60. Which is very hard and non-flexible.
So they have to de-rate the tubes using the new material.
Once it glows red..., its dead.

Some sweet spot.., yeah vow.

Take Care

Ivey

[defaced]

What's your source for this info?

[ivey]

100 watts from 35 watts..., it is very simple in the radio world

Just add the input power needed to drive your linear rf power amp to full output.

By adding the wattage used to drive the unit to the power need to produce the output, you get total power wattage of the complete system.

Even thou total input power does not mean total output power.

Numbers game.


Ivey

[ivey]

It only make sense.

If the tube enters are all the same. Then it has to be the materials. Something have to change.

To reduce the speed and power in a car with the same engine, you reduce the carbs or the gas amount being fed into the engine.

The materials have to change. Just check with the development of tubes through the 1930's to the 1950's. The type of materials used and the size were the factors. If everything is the same size inside and out of the tube. The materials are the only remaining factor left.

Even if they change the cathode heaters, they reduce the current on the tube heaters; in order to get it to reduce its space cloud.

What would cause the heater to require less current. The material it is made of is reduce in size or length, requiring less filament current.

Yes or No

Take Care

Ivey

[ivey]

They change something in the tube.

The 6SN7 and 12AU7 are the same tube. But power wise, the latter is much smaller and produce less wattage/power output. Size and materials made the difference. They do the same thing, but the 6SN7 has a larger output.


Take Care

Ivey

They are claiming..., what? Same size, same materials. No way.

Take Care

[Steve Conner]

Ivey, I'll have some of what you're on!

Here is the straight dope once and for all on power ratings.

In a Class-B linear amp with ideal output devices, operated just on the edge of clipping, the efficiency is 70%. That comes from the math behind making a sine wave out of DC.
(reference: Amplifier Efficiency)

Therefore, an amp rated at 100 watts will have to draw 140W from the HT supply, and dissipate the 40W difference in its output devices. So, two tubes with 20W plate dissipation would do. Philips' maximum rating for their EL34 came close: EL34s have a plate dissipation rating of 25W, and they claimed 100W from a pair running on 800V B+. That's only 10 watts of "non-ideality", pretty good for vacuum tubes.

Biasing into Class-AB so that the devices are already hot before any signal even hits them, using non-ideal output devices such as vacuum tubes that drop 50 or 100V even when turned fully on, all eat into this figure: you get less output for a given plate dissipation. Many people think that the idle power dissipation in a Class-AB amp is equal to the output power: it's not. It's a waste that takes away from the output power, but we tolerate it because it decreases distortion. A Class-B tube amp is too distorted even for guitar.

[MWJB]

Power output in AB, in excess of the tube's rated plate dissipation is easily accessible...it's the "clean W RMS" that's the sticking point. You can get 100W from 2xReflector 5881WXT, but it's not clean. Fender get 55-58W "clean W RMS" from the same tubes, which is pretty close to extracting power that matches plate dissipation...that's if anyone really knows what that tube's plate dissipation is, we can assume it's at least a 27.5W to 29W tube?

[defaced]

If the tube enters are all the same. Then it has to be the materials. Something have to change.

To reduce the speed and power in a car with the same engine, you reduce the carbs or the gas amount being fed into the engine.

The materials have to change. Just check with the development of tubes through the 1930's to the 1950's. The type of materials used and the size were the factors. If everything is the same size inside and out of the tube. The materials are the only remaining factor left.

Even if they change the cathode heaters, they reduce the current on the tube heaters; in order to get it to reduce its space cloud.

What would cause the heater to require less current. The material it is made of is reduce in size or length, requiring less filament current.

Yes or No

Take Care

Ivey

I agree, changing the materials makes sense, I was just wondering where you got Monel from. I couldn't think of why a nickel/copper alloy would be used for the anode. Monel alloys are usually used for corrosion resistant and high temp strength applications.

[Steve Conner]

I heard that the plates were made of molybdenum, or iron, or some combination of metals laminated together, maybe to stop it warping under extreme heat.

This is the first I've heard of monel being used.

Also I thought space heater elements were made of Nichrome.

[defaced]

NiChrome is very common for heating/resistive elements in general (stove, hair dryer, industrial load banks, etc). The typical compositions are resistant to oxidization at elevated temperatures which keeps them from scaling in service. If you've ever seen a video of steel making, you'll notice the large chunks of stuff flaking off, that's the iron oxide scale. That said, assuming the vacuum inside a tube is relatively void of oxygen (<10ppm or there abouts), oxidization and scaling wouldn't be an issue.

As for lamination, I'd think it'd be more like a coatings/thermal spray of a super duper secret electron catching whizbang composition. As to what's in the coating, assuming it's coated, who knows.

[ivey]

Yes my brothers:

That is what they do.


We get screwed by these manufactures into thinking we are getting our monies worth. It is not until you get into the game that you discover that it is fake.

I finish U of Penn, in 1952, as a electronics engineer. My god, before I knew it, I was paddling the same lie. I had to pay bills and feed myself. And marriage only made it bearable.

Take Marshall. He copied the Fender Bass man Amp. By all rights he violated Fender's rights. But he was smart enough to change the preamp tube from a 12AY7 to a 12AX7, plus change the mixing resistor from 270k to 470k. And then charge a small fortune for it. Claiming 45 watts of power. Yes it is, RMS, not brute power.

Take a look at the Heathkit TA-16, it claims ungodly music power, yea right. Not out of those transistors.

Engineering shows that, in order to get up to a power level, you must burn power, in the form of heat. Lots of heat. Like a car, it is economical when cold, once it is hot, you lose power. Because the engine must turn the tranny and the tranny must turn the wheels and the wheels get hotter as it meets the road surface, creating more heat, causing wear. Which increases drag. More drag, more fuel, more heat, less power. And we all try to meet in the middle. Harmony.

So the engine on a dynamo, its power is static power, not dynamic power. And we all know that auto makers love to use dynamo power specs. Hell, there's no car body, drag, weight, or transmission issues to worry about. Great engine!!!!!!!!!!!!

So if JJ sells these tubes, it will be 9 watts SE or 18 watts PP. Which is really only 5 watts and 12.5 watts respectively. Remember wasted heat.

You see my brothers, they are going to give a little and take a lot. A lot of our money that is.

I just love the "Industrial Revolution".


Take Care

Ivey