WA-44C Vacuum-Tube Audio Generator Samples

The WA-44C is a vacuum tube audio generator that was sold by the Radio Corporation of America from the mid 50's to the early 60's. From the manual:

"The RCA WA-44C Sine/Square Wave Audio Generator is designed for general radio work, and other applications which require a sine or square wave audio-frequency signal. The instrument is ac operated from a 50-60 cycle, 105-125 volt source, and covers a range from 20 cps to 200,000 cps. This Sine/Square Wave Generator can be used for a wide variety of applications, including the direct measurement of the frequency response characteristics of audio amplifiers, and the testing of loudspeakers and enclosures. In addition, the WA-44C can be used in finding the impedance of LC combinations, and in determining the frequency or speed of vibrating or rotating bodies."

The unit uses one 6AQ5, one 6X4, and two 6U8A tubes. The sine wave is developed using the 6AQ5 and the pentode side of one 6U8A with an incandescant bulb in the feedback circuit, a standard oscillator design at the time. The square wave is made by clipping the sine wave through the triode side of both 6U8As.

Before I recorded the samples, I replaced any of the electrolytic and paper-in-oil capacitors that I could (not all of them because some are weird). I checked and found several out-of-tolerance carbon composite resistors, but chose to leave them as-is because I don't want it to be too perfect!

The sine wave in particular from this unit has a unique character, as can be seen on a scope. Probably from out-of-tolerance components. Maybe.

Interestingly, the frequency dial is not a potentiometer as one may expect - it is a large air-gap capacitor, of the type typically seen in radio tuners. At the time it was widely held that it was easier and less expensive to use variable capacitance - rather than a variable resistance - as the control element in any kind of oscillator or filter design.

I only recorded a series of E notes for the sine wave and I didn't record any sharps or flats for either wave. The waveforms don't change appreciably throughout the sweep of the dial, so I thought it would be a waste of time.

Each sample is cut at zero crossing and will loop seamlessly without any further modification.

https://www.disasterelectric.com

https://disasterelectric.gumroad.com/

https://ko-fi.com/disasterelectric