How to Build an Electric Organ FOR ABOUT FIVE DOLLARS (Apr, 1933)

How to Build an Electric Organ FOR ABOUT FIVE DOLLARS

WITH its deep, mellow notes, the electric organ is fast gaining the musical limelight. As a rule, these instruments are large and costly. Yet, for the price of a new hat, you can build a duplicate of a small organ that was featured in a recent coast-to-coast radio broadcast.

Complete, the original instrument cost its designer, Elmore B. Lyford, a New York electrical engineer, a little more than five dollars. In spite of its low cost, its rich organ-like notes delighted the well-known radio pianists that fingered its keys and its simplicity interested the engineers that examined it. All you need to build the organ is nine 50,000-ohm variable resistances, a .003 microfarad condenser, some brass, a type ’74 voltage regulator tube, a socket, and a few feet of insulated connecting wire. For power, the organ uses three forty-five-volt B-batteries.

Although the organ can be connected directly to a loudspeaker, best results are obtained if an audio amplifier is used with the speaker. Of course, if you have a modern radio, you can use its amplifier and speaker by making connections to the detector tube or through the phonograph jack attachment. In the photograph, a separate amplifying unit and speaker are shown.

The keys can be bent from strips of brass or ordinary push buttons can be used for the contacts. In fact, if you are really ingenious, the key-hoard of an old toy piano can be rigged as your electric console. Although only eight keys, corresponding to the scale, were used in the original, more can be added to obtain the intermediate tones.

With the tube in place and the organ connected to the speaker circuit, you are ready for the simple tuning operations. As shown in the diagram, each key circuit contains a variable resistor. This resistance controls the tone of the note formed when that particular key is pressed. The resistances should be adjusted until each key, starting at the left, produces a note in the scale.

The master resistance, marked A in the diagram, controls the tone of the entire range. Increasing this resistance lowers the entire tone of the scale and decreasing it raises it. When you play the organ press only one key at a time. In the beginning start with a simple tune, and you will be surprised how easily you can pick out the notes by ear. As each key is pressed, your loudspeaker will reproduce the notes in the rich tremolos characteristic of a fine organ.

14 comments
  1. Greger says: October 15, 20071:58 am

    And it uses only three 45 volt batteries.
    Now where can I get those? (Along with a type ’74 voltage regulator tube)

  2. jsiren says: October 15, 20072:23 am

    I understand that these articles are reprinted for informational and amusement purposes only.

    As a quick note, however, even considering the 1933 safety standards, I do wonder about the sense in putting a ground connection on the negative side of the battery, with the keys on the positive side, effectively putting +135 V at the user’s fingertips. Ground the user and you have an accident waiting. (Lemme just adjust this… *bzzzt* that felt funny… didn’t sound right… *BZZZT* strange tingling, better sound… what if I turn this all the way down? **ZAP** ouch.)

    Playing the pictured device must have been an electrifying experience, if not hair-raising… Especially so if you happen to touch any part of the loudspeaker circuit at the same time. (Why isn’t this making any sound? lemme just wiggle th**ZAP**ouch.)

  3. dj_nme says: October 15, 20073:46 am

    It looks quite simple and shouldn’t be dangerous if you use push-buttons from Jaycar or DSE.
    The only problem would be finding a modern replacement (preferably solid-state) for the type 74 tube.

  4. carlo says: October 15, 20074:13 am

    Wonderful vintage schematics! But i would modify it to have the keys connected to ground and not to high voltage, otherwise would be better to use plastic keys to avoid ZAPs on the fingers…

    This is a common relaxation oscillator so i think that a common neon lamp could be used instead of the “type ‘74 voltage regulator tube”. With a noeon lamp a lower voltage around 100V would be enough to work as those neon lamps start their negative resistance behaviour around 70V.

  5. Jonathan says: October 15, 20079:55 am

    This circuit could be modified to use a Wein-Bridge oscillator negating the need for the tube and therefore the 100+ volt supply. Of course you wouldn’t get the same warm glow from the op amp—well if you hook it up correctly that is.

  6. JMyint says: October 15, 20072:30 pm

    If’n ya look about on the web there are instructions on making a ‘B’ battery. I looked through my list of obsolete tube types but I couldn’t find a type ’74. From the way it is depicted in the schematic it is a rectifier tube that uses the heater as the emitter. These types of tubes kinda disappeared from the scene in WW2.

  7. carlo says: October 16, 20072:37 am

    Hi,

    I explain better why you can use a neon lamp, the principle of this organ, that is merely a relaxation oscillator is the following:

    First of all, the loudspeaker must be connected to the tube and ground, otherwise this will not work at all!
    A current provided by battery and limited by the selected resistor is charging the capacitor until the voltage across the tube reaches his higher trigger threshold (for neon lamp is around 70V), then the tube immediately discharges the capacitor until it reaches the lower trigger threshold (not sure about this, let’s say about 50V), then the tube goes off again and the cycle restarts. This gives a frequency proportional to the RC value with current pulses through the loudspeaker (not a mellow timbre!). So a neon tube would do the job.

    Anyway, because musical scale is not linear, the “main tune” potentiometer directly connected to the capacitor will NOT transpose the scale but only make it out of tune, because you need to multiply or divide the currents for a factor to get a transpose function (by two for one octave transposition) and just not add or subtract a resistor.

    The easiest way to transpose this “organ” main tune is to change capacitor, this would leave the correct intervals between the notes :-)

  8. carlo says: October 16, 20072:41 am

    P.S. for neon lamps i mean those small orange glowing lamps and not fluorescent tubes, is common to call them “neon tubes” but they would not work at all.

  9. Flokater says: October 22, 20074:29 am

    I think the tube is a RE074 from Telefunken.
    Datasheet can be found here:
    http://datasheets.elect…

  10. GalFisk says: January 21, 20082:20 pm

    RE074 is a regular triode, this needs to be a gas filled tube as JMyint explained.

  11. Nick says: March 29, 200811:24 am

    Im trying to learn how i could use this method to produce hydrogen , much like stanley meyers did in my honest opinion it was using resonance and tuned organ pipes if you will

    someone please help me http://www.myspace.com/…

  12. jayessell says: November 19, 200812:19 pm

    a) Yo, I’m certain the 555 IC has a diagram that performs this function with only 5 volts DC.
    Whoops! Here it is: http://www.josepino.com…

    b) Nick, are you trying to electrolyse water into hydrogen and oxygen using less power than the chemistry books say you need? Trying to exceed 100% efficientcy? TANSTAAFL.

  13. Keagan says: April 26, 20104:12 am

    Is it cheaper to build an organ or to buy one?
    Is it possible to build on on your own without any experience?

  14. Erik says: September 9, 20113:07 pm

    Someone said find a “preferably solid-state replacement” for the 74 tube? Eww, I can’t imagine doing that, intentionally replacing a tube component with something else.

    That being said, while this is drastically simple, it is a pretty good starting point for making a proper organ.

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