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[RMoore]

There was a thread about DIY PA systems on John Klett's forum: http://recforums.prosoundweb.com/index.php/t/8715/2606/?SQ=a 2cdace328792cbcf2884e79307990a4

Justin from Pheonix raised the idea:

<quote> What you want really is a monster amp with a stack of 4CX250B tetrodes running in parallel push-pull mode, with a B+ of about 1Kv - just what the doctor ordered for dub <quote>


This has gotten me very interested in the idea of radio xmitter tubes for audio amplifiers,

Does anyone know if this is really feasible in practice?
Would the resulting sound be anything near pleasant to listen to?

My guess is if it were possible someone would have done it by now..

Note I am not a designer or electronics technician  -  I am just fascinated by this idea & inquiring minds need to know!

Thanks for your thoughts!

Ryan

[Spock]

You know you are a few years too late to see a real life example.

I live very close to what was a Voice of America (VOA) site in Ohio.  Over 30 years ago I got a tour of the place, most of the guys that worked their were amateur radio operators, so they gave others hams, the real niffty tour.

Anyway to make an AM transmitter the audio part has to supply one half of the power.  So to make a 100 watt transmitter, the B+ supply to the main output tubes is run through the output transformer of a 50 watt audio amp.

These guys had transmitters (yes more than one) that could put out 500K watts.  Also a bunch of smaller ones.  I remember standing next to the audio output transformer, it was as tall as I was at the time.  A few of the laminations were not tight, so you could hear the program going over the air just from the the metal vibrating.

Right down the street, from the VOA site, now a park.  Is WLW AM 700, 50K watts.  so they have a 25K audio amp.

Heck you down need a stack of tubes, we had a few RF amps around the house, 1K watt, one tube.

The problem is not the tube, but the power supply.  The voltages start to get high, so you need more air space around everything.  Also cooling.  Mainly fans for our stuff, the tubes VOA used were water cooled, and heating the buildings in the winter.


Edit....


Oh and before you ask, yes the tubes had to be run so they were linear.  If you didn't do that, then you would splatter trash outside of your assigned bandwidth and stomp all over some other station.  And then the you would get a visit from the FCC.