21kW audio power amp?

[SpreadSpectrum]

Sometimes I come into contact with interesting tubes and I enjoy looking at the data sheet. I knew that this one(ML-7120) was a transmitting tube of some sort, but what shocked me was the inclusion of data for use as a class AB1 AF power amp.

Here is the data sheet:

7120.pdf

Highlights from the data sheet:

Filaments: 7V, 85A. 400A cold.
Max plate voltage: 10kV
Plate dissipation: 12.5kW
Peak grid-to-grid voltage: 4.6kV
Power output: 21kW

Seriously, has such an audio amplifier ever been made?

[dr f]

If they have made an amp of this size, I'd like to know where they sourced the power from to run it? Maybe it could be powered direct from the power lines in the street?

[w5jag]

Modulator, probably.

Win W5JAG

[SpreadSpectrum]

Modulator, probably.

The data is for an AF amp(there is separate data for use as an RF amp).

I guess I just assumed that the up-converting or mixing or whatever would be done before the final output stage. Is there a way to do it after?

[SpreadSpectrum]

From looking at a radio station schematic, I guess I don't really understand how AM/FM radio transmitters work, but it seems that up-converting can occur at a pretty high level.

Oh well, I guess I can't build a stereo out of these things. I thought that was what they were implying in the data sheet.

[w5jag]

You can modulate lower level stages and then mix them up to the desired frequency, and amplify that. That doesn't produce the best quality of audio.

I've even used severely unbalanced balanced modulators to make crude AM transmitters.

The preferred way to produce AM is to directly modulate the final amplifier stage, and that's what these high power AB1 amplifiers were used for. If you listen to a good high level AM transmitter on a quality receiver with a flat passband, they sound really good.

Lots, maybe most, of the RF tubes were used for high power modulators.

Win W5JAG

[hitsware]

>I guess I can't build a stereo out of these things.
>I thought that was what they were implying in
>the data sheet.

You can. I'd go for a little more modest power as to not have to have either the fans or pumps running.

[w5jag]

Originally posted by SpreadSpectrum
From looking at a radio station schematic, I guess I don't really understand how AM/FM radio transmitters work, but it seems that up-converting can occur at a pretty high level.

http://www.wa3key.com/kw1.html

Block diagram of a quality AM transmitter from the golden age.

Win W5JAG

[SpreadSpectrum]

...as to not have to have either the fans or pumps running.

Yeah, that could be noisy, but you'd have plenty of power to cover up the noise!

[Zap]

Originally posted by w5jag


Block diagram of a quality AM transmitter from the golden age.

I've always wanted to own one of those.... nice to see at least a few of us appreciate the RF side of tubes as well