The company I work for is in the midst of cleaning out a studio location. Most radio engineers are some form of pack rat. I know I have been guilty of this myself, not wanting to throw something away because tomorrow, it might be needed. That was carried out to the extreme at this location. One of the things that I found in my clean out was a Western Electric 212E vacuum tube.
It is an impressive thing, measures about 12 1/2 inches tall, including the pins. I am thinking this is pretty old, it probably came from a pre-WWII Western Electric AM transmitter. This would make the most sense, as the station signed on in 1926 with 250 watts. Back in the day, Western Electric was the patent holder for AM technology. In fact, there was some talk of suing General Electric for patent infringement after the airing of the world series by WJZ and WGY in 1922. Parent company AT&T was working on radio modulation techniques to implement with their telephone system.
These tubes were used for audio amplification, according to the spec sheet, the plate could dissipate 275 watts. Filament voltages is 14 volts at 6.2 amps, the plate voltage was 3,000 volts, maximum. It is a tetrode. The RF counterpart to this tube is the WE 308A.
From what I am to understand, these have not been made since 1960 or so. I also understand there there is quite a cult following for this tube amongst Asian audiophiles. There are several examples of extremely low distortion class A and AB amplifiers using this tube type. Some prices on Ebay are in the $1,500 to $2,000 per tube range. Unfortunately, I don’t think this one works anymore as there is a loose screw and little bits of what looks like control grid wire in the bottom of it. It does light up with 12 volts on the filament, however.
I am a strong proponent of non-computer based air chain processors. Something about listening to dead air while the computer reboots is annoying and every computer needs to be rebooted every now and again.
All of that being said, I recently had a chance to play around with Breakaway Broadcast audio processing software. I have to say, as a low cost, very versatile platform, it can not be beat. I would put it up against any of the high end FM audio processing, provided one uses a high quality sound card with an adequate sample rate.
Claesson Edwards Audio has developed several software based audio processors for a variety of end uses. They make several recommendations for hardware and operating systems, Pentium 4 3.2 GHz or better, dual core preferred. If one is interested in used the sound card to generate composite audio, then any sound card capable of true 192 KHz sample rate will work. They list several that have been successfully tested on their web site.
For approximately $1,200 dollars or so, one could buy a decent computer, the Breakaway Broadcast software and the Airomate RDS generator software. For a Mom and Pop, LP or community radio station that is looking to do some high end audio processing and or RDS, that is a good deal. I would add a UPS to the computer and keep back up copies of the software installed on an emergency computer just in case. One can never be too safe when it comes to computers, viruses, hackers and other malicious persons.
Things that I like
Inexpensive, the fully licensed version is $200.00. The demo version is free but there is a 30 second promo every thirty minutes.
There are several factory presets, but everything is fully configurable, changes can be named and saved allowing some experimentation.
Audio cards with 192 KHz sample rate or greater can be used to generate composite audio, eliminating the need for a separate stereo generator
RDS capable with additional software (Airomate2, approximate cost $35.00)
The same processing computer can be used for streaming audio and or AM audio processing simultaneously.
Full set of audio calibration tools for AM and FM transmitters, allows correction for tilt, overshoot and linerity. Can add pre-emphasis at any user selectable rate.
Fully adjustable phase rotators.
Things that I don’t generally like:
Computer based system using Windoze operating system
WXPK in White Plains, NY has been using this software to process their streaming audio for about 2 years now. The software itself is extremely stable running on a stand alone Windows box with XP service pack 2.