The 126 Vacuum Tube Theremin

Published August 23, 2002
Updated April 2, 2022

Contents

Legal Notice
Safety Notices
Acknowledgments
Introduction
Circuit Description
Schematics
Construction
Test Voltages
Photos
Parts Tables
Drawing Index

Parts Shortage

The X1 Crystal, L1,L2 and L3 coils and C5 and 24 variable capacitors are depleted.

Update Notice

This version of the 126 Vacuum Tube Theremin consolidates previously-published editions.

The author is delighted that the 126 has enjoyed such unprecedented, long-term attention,
resulting in the construction of dozens of instruments since its original publication, 20 years ago.

Please feel free to contact me, should you need documentation from previous editions of this article.

About Cost

I receive many inquiries asking about the cost of this project. Unfortunate circumstances due to the
2019 pandemic and the ensuing impact on parts availability and prices along with outright price gouging
among many manufacturers and distributors have caused an unprecedented increase. For informational
purposes, I have included costs in the last column of the Parts Tables. Some items, such as wire, are
especially expensive, and as a compromise, I have left separate line-item pricing for hook-up wire
colors other than black out of the cost. This will alter the construction methods to some degree.

As of this update on April 2, 2022, the total Parts Tables items cost is $1149.05.

On a related topic, many inquiries regard the commercial availability of the 126 theremin from
Harrison Instruments, Inc. as a finished product. It is presently not available as a finished product
and will not be available until a sufficient order is made which would justify the production costs
For this type of instrument, this would involve a minimum of 100 units.

Notice to Builders Outside the United States

 To assist builders outside the United States, items C5 and C24 (variable capacitors), L1, L2, L3 (coils),
and X1 (ceramic filter) are available as a kit from eBay as item 201981928615.  
Builders within the United States should order these items from Harrison Instruments.

Spot an error? (technical, grammatical, or speling)
Please send me an e-mail!

Legal Notice
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.

Safety Notices
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• The circuit described in this article uses AC mains voltage and other high voltages that can cause injury or death. It is the responsibility of the user of this circuit to be familiar with all applicable safety practices regarding its construction, testing, and use.
  

• Some parts used in this circuit only function properly when inserted in the right direction. Always verify the orientation of polarized capacitors, diodes, rectifiers, transformers and vacuum tubes before applying power to them. Do not use a part that has been subjected to improper insertion.
  

• The vacuum tubes in this circuit become hot and can cause burns.
  

• Wear safety glasses and use all appropriate safety equipment when working with tools and materials. Always follow safe shop practices and obey safety rules.

Regarding the safety of your ears and hearing:

• Do not play this instrument at a high volume, especially when using headphones. Use headphones that have a built-in volume control, and adjust the volume for a comfortable level. Hearing experts advise against the continuous, extended use of headphones.

This circuit is recommended for users familiar with electronic theory and construction practices. It is recommended that suitable test equipment, including a frequency counter and oscilloscope, are available for making measurements.

Acknowledgments
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I express my sincere thanks to John Speulstra and Rick Hansen for their assistance in refreshing my knowledge of vacuum-tube techniques, and also to Steven Hasten for providing me with the incentive to pursue this design, and his construction efforts in verifying its performance. I also express my sincere thanks to Chris Fazi and Roger Kaul for assisting in the analysis of the volume control circuit design.

Introduction
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This is my second vacuum-tube theremin design, which is an expansion of its predecessor, the pitch-only 125 theremin. The 126 theremin has both pitch and volume features, as well as a tone control.

As in the 125 theremin, I have designed the 126 entirely with the popular 12AU7 vacuum tube. The pitch section consists of the classical two-oscillator heterodyne configuration, and the volume section employs a slope-detection method, with a ceramic filter. The ceramic filter provides the high selectivity required for the small frequency changes induced by hand capacitance, replacing the elaborate and costly inductor-type circuits usually used for this purpose. As with the 125 theremin, exceptional frequency stability for temperature variation is achieved, both in the pitch and volume sections.

The 126 theremin is designed with a plate-antenna configuration, capitalizing on the hand-to-plate coupling efficiency offered by this method. As with most of my dual-parameter theremins, two horizontal 8-inch by 5 1/2-inch rectangular antennas, extending from each side of the instrument, provide the gestural interface. The 126 theremin exhibits at least 5 octaves of pitch variation over a sensing distance of about 18 inches, and at least 45dB of dynamic volume range (closer-for-louder mode), over a sensing distance of about 10 inches, as illustrated in the following graphs:

126 Theremin Demonstration
©1958, Sammy Fain, Paul Webster

Circuit Description
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Vacuum tube V1A and its associated components form a Colpitts oscillator that includes hand capacitance, via antenna A1, as a frequency determinant. 455 kHz ceramic filter X1, driven by the oscillator via C7, performs the function of a frequency-slope detector. With the hand away from the antenna, the oscillator frequency is at resonance with X1, and the greatest amplitude sine wave is present at X1's output. As the hand approaches the antenna, the oscillator diminishes in frequency, resulting in a diminished amplitude at X1's output. Note that the center frequency of the ceramic filter is 455 kHz when used in a radio receiver with a specific intermediate-frequency transformer. However, in this application, the filter is less "loaded," and will exhibit a center frequency of about 458.5 kHz. The use of such a filter is particularly efficient in the design, since it permits a very low component count.

V1B amplifies the sine wave at X1's output, as well as providing impedance matching between X1 and the following circuit. The output of V1B is AC-coupled through C9 to V2A, a diode-configured triode used as a DC restorer, that establishes the bottom of the voltage waveform at about zero volts. As a result, the volume hand's proximity controls the positive-peak amplitude of the sine wave present at the grid and plate of V2B, a second diode-connected triode, which, in conjunction with C10 and R7, provides a DC voltage level corresponding to the peak value of the V2A sine wave. As the hand nears the antenna, the positive DC voltage at V2B's cathode diminishes.

This DC voltage level is applied to the grid of V3A via R8. Also applied to V3A's grid is the audio pitch waveform, via DC blocking capacitor C11. The resulting amplitude of the audio pitch waveform at V3A's cathode depends on the value of the DC voltage level from V2B, since V3A's conductance varies in accordance with that level.

Next, the signal is applied from V3A's cathode to V3B's cathode. V3B's grid has a switch-selected condition for either ground, or about +4.1 volts, via voltage divider R30 / R31. This provides a means to select V3B's operating point, allowing either volume response. Note that each section of V3, for most combinations of volume mode and hand distance, have their cathode potentials above the grids. This configuration provides a unconventional, but efficient, circuit solution. The following chart indicates V3 voltages. Measurements were made with B+ = 45 VDC, and a tone frequency of 440 Hz. AC voltages are peak-to-peak.

The pitch circuit is shown on schematic page 2, below. V4 and associated components form a Colpitts oscillator that includes hand capacitance, via antenna A2, as a frequency determinant. Another oscillator, comprised of V6 and associated components, is the reference oscillator. The oscillators employ cathode-follower sections, V4A and V6A, to buffer their resonant networks from loading effects and to provide low impedance outputs. V5B is used as a mixer, with the pitch variable oscillator signal applied to its grid via capacitor C19, and the pitch reference oscillator signal applied to its cathode via resistor R21.

With tone-control potentiometer, RV1, in the extreme counterclockwise position, the reference oscillator output is coupled to the mixer via C28. Electrical coupling between the two oscillators occurs because the signal at V5B's cathode includes the signal present at it's grid. This signal, from the variable oscillator, is reflected back into the reference oscillator, via V6A's cathode. Under this condition, the maximum amount of oscillator coupling produces the greatest amount of harmonic content in the audio waveform.

With RV1 in the extreme clockwise position, the reference oscillator's output is isolated from the mixer via V5A. In this condition, the mixer's cathode signal has less influence on the reference oscillator, because it is attenuated by RV1's 50 kohm resistance. As a result, the harmonic content of the audio waveform is comparatively reduced.

The heterodyne of the two oscillator frequencies is present at V5B's plate. Two sections of low-pass filtering reduce the sum frequency product; C21 in conjunction with V5B's plate-circuit resistance, and R22 with C22.

The oscillator frequencies are described by the following equation:

For the volume oscillator, L is 1 mH, Ca is 330 pF, Cb is 100 pF, and Cc is the sum of C5, C6, and the A1 antenna capacitance. C5 is adjusted so that the volume oscillator's frequency is equal to X1's resonant frequency of 455 kHz with the hand away from antenna A1.

For the pitch oscillators, L is 1 mH, Ca is 1000 pF, Cb is 330 pF, and Cc is the A2 antenna capacitance (for the variable oscillator) or the value of the C24 pitch-zeroing capacitor (for the reference oscillator). Each of the pitch oscillator frequencies are typically 310 kHz.

As in any heterodyne theremin, an essential requirement is that the two pitch oscillators are very close in frequency, so that an audible tone can be produced. Optimally, the theremin should provide a "zero-beat" condition with C24 set to its mid-capacitance point, with the hand away from the pitch antenna. A low frequency audible output should result when the hand is brought within 12 to 24 inches of the pitch antenna, increasing in frequency as the hand becomes closer.

In most instances, component tolerances will cause the pitch oscillator frequencies to be too far apart to produce an audible tone, so a calibration procedure must be performed. To do this, measure the frequency of the pitch reference oscillator by connecting a counter to the cathode of V6A, and record that frequency. Then, move the counter to the cathode of V4A, which is the output of the variable oscillator. With variable capacitor C24 set to midpoint, and antenna A2 clear of objects, adjust the frequency of the pitch variable oscillator to match the recorded frequency, with one or more of the following methods:

• To reduce the pitch variable oscillator's frequency, add a small mica capacitor with a value between 2 and 30 pF in parallel with its coil (L2).
  
  
• To increase the pitch variable oscillator's frequency, replace 330 pF capacitor (C17) with a 300 pF mica capacitor, and then, if necessary, add a small mica capacitor (with a value between 2 and 15 pF) in parallel with the 300 pF capacitor to "trim" the frequency back downward.
  
  
• Move L2 toward or away from the theremin mounting plate; toward the plate for decreasing frequency, and away from the plate for increasing frequency.
  

Volume circuit calibration is performed by observing the RF voltage waveform at V1B's cathode. With C5 approximately centered and the hand away from A1, the waveform amplitude should peak, indicating volume oscillator resonance with X1. This corresponds to the center frequency of X1, which is 455 kHz. If this condition can not be obtained, then the volume oscillator's frequency may be adjusted with one or more of the following methods:

• To reduce the volume oscillator's frequency, add a small mica capacitor with a value between 2 and 10 pF in parallel with C6.
  
  
• To increase the volume oscillator's frequency, reduce the value of C6, or remove it.
  
  
• Move L1 toward or away from the theremin mounting plate; toward the plate for decreasing frequency, and away from the plate for increasing frequency.
  

To eliminate the necessity for extensive trimming, the capacitors associated with the three oscillator frequency-determining networks (C2, C3, C6; C16, C17; C25, C26) should have ±5% or better tolerances. To ensure good frequency stability, these capacitors should be mica types, and the three oscillator coils, L1, L2, and L3 should be the J.W. Miller 4652 phenolic-core types specified. Capricious substitution of the coils may adversely affect or inhibit the theremin's operation.

Also, for frequency stability, C5 and C24 should be air-variable types. Too much capacitance change per degree of shaft rotation will degrade adjustment resolution. Therefore, a maximum value of 27 pF is recommended. Variable capacitors with a planetary reduction vernier will further enhance resolution. Such capacitors, with 3.85 turns of shaft rotation, are indicated in the schematic, and highly recommended.

The overall frequency of the theremin's operation may be changed with the substitution of frequency-determining components. However, the values indicated, providing approximately 310 kHz in the pitch circuit and 455 kHz in the volume circuit, were selected to prevent AM radio-band interference, while maintaining adequate hand-sensing distances.

The tone control's position has a slight effect on the pitch reference oscillator's frequency. Therefore, changing the tone will require a minor readjustment to pitch zero capacitor C24 for resetting the zero beat. However, this readjustment can be achieved easily.

The power supply is shown on schematic page 3, below. Voltage regulation is not employed in this circuit, since the oscillators exhibit excellent frequency stability with considerable supply variations. The total current drawn from the 50 volt supply is approximately 4 mA. Heater transformer T2 is rated to provide 10 volts RMS for a 1.2 A load. The six tubes use approximately 900 mA of heater current, so T1's actual loaded output is about 11.5 volts RMS, which is adequate for the 12.6 volt-rated 12AU7s or ECC82s. The theremin's parameters stabilize after a brief warm-up period of about three minutes. Thermal coefficients in the circuits have negligible contribution to long-term drift, with parameter readjustment only required due to shifts in the player's stance, or pitch readjustment when the tone setting is altered.

Some builders may wish to use alternative transformers to match their available mains voltage. If different transformers are used, measure the supply's output voltages while the theremin is connected, to ensure that the heater voltage is between 11.5 and 12.6 volts RMS AC, and that the B+ voltage is between 45 and 50 volts, DC.

To reduce the risk of injury, I designed this theremin with a maximum supply of approximately 50 volts, DC, which is considerably less than voltages used in many other vacuum-tube instruments. However, values substantially less than 50 volts can still be dangerous for conditions in which sufficient current is caused to flow through the body. Therefore, 330 pF ceramic capacitors C4 and C15 provide a safety function by preventing the presence of +50 volts on the antennas.

SAFETY NOTICE:

• Do not omit capacitors C4 or C15 from the circuit.

Schematics
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Construction
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The 126 theremin, illustrated below, is constructed on a 8" x 12" x 1/16"-thick aluminum chassis plate refered to as the Theremin Mounting Plate . It is attached to a 11" x 17" x 1/2"-thick plywood Base with four threaded standoffs. The volume and pitch Antennas are 8" x 5 1/2" x 1/16"-thick aluminum plates that extend from the left and right edges of the base, respectively. The antennas are separated from the base with 1/2"-long threaded nylon standoffs to reduce their mutual capacitance, and connected to the circuit with 16 gauge solid bus wire. The wires are connected to the antennas with number-6 solder lugs, secured by one of the mounting screws at each antenna. The bottom of the base (not shown in the illustration) has an Atlas Sound type AD-11B threaded microphone stand adapter.

The theremin's components, including two connectors and their brackets, are mounted on the bottom of the theremin mounting plate, with the tube envelopes and the control shafts for C5, C24, and RV1 on the top. The six 3/4" holes for the tube sockets and two 5/8" holes for the variable capacitors can be made with chassis punches (Greenlee types 730BB-3/4 and 730BB-5/8).

Refer to the Component Locations drawing. Screw-mounted Insulated Solder Turret Terminals provide junction points. Where required, component leads are insulated with 16 gauge Teflon® sleeving. Point-to point wiring is used, with 22 gauge, 19-strand Teflon®-insulated hookup wire, and 20 gauge solid tinned-copper bus wire, as required.

Regarding insulated hookup wire, the parts tables specify a variety of colors based upon wire function. Although color differentiation is good practice and recommended for electronic construction, the builder may economize by using only one color.

SAFETY NOTICE:

• Note that black wire is specified for the transformer primary line connections, and also for the DC return connections. To prevent shock hazards, do not confuse the dual functions of black wires.

Wires are anchored to the theremin mounting plate, as required, with adhesive-backed mounts and nylon cable ties. Leave a little slack in the leads of the three coils so that they can be moved with relation to the plate. This technique permits small variations in capacitance that may be used to fine-adjust oscillator frequencies. Keep frequency-determining components C2, C3, C6, C16, C17, C25, C26, L1, L2, and L3 clear of other parts and wires. To prevent audible hum from the heater circuit, twist the heater wires tightly together and route them in a direct manner away from signal paths.

Ceramic filter X1 has relatively delicate, closely-spaced leads, nominally intended for printed-circuit board installation. To adapt X1, it is recommended that its center lead be soldered directly to the top of its respective turret terminal, and that short pieces of 20 gauge bus wire are soldered to the outside leads at right angles, and extended to the tops of their turret terminals. A version of the filter is also available with strain-relieved wire leads attached, as Harrison Instruments item number 99999-5915-126X1-1.

While assembling components onto the theremin mounting plate, temporarily attach four pair of long standoffs to the corner holes to protect the components from being damaged by the work surface:  Four 2 1/2" female-female standoffs on the top side of the plate, and four 2" male/female standoffs on the bottom. Each male/female standoff has a stud inserted through its hole to engage a standard spacer. Once all the parts have been assembled onto the plate, the temporary standoffs may be removed, and replaced with four 1 1/4"-long standoffs which are used to attach the plate to the wood base. Note: Apply a small amount of wax or oil to the male thread of the male/female standoffs before coupling them with the female standoffs, to prevent seizing.

Ground wiring may be "daisy-chained" in any convenient manner. Run a wire from each chain, as well as terminal 1 of power connector J1, to a single point on the theremin mounting plate. The J2 output jack is a fully-insulated type, to prevent audible hum from ground loop currents. Its sleeve terminal connects to the single-point ground, as well. Variable capacitors C5 and C24 have their "rotor" terminals connected to their frames, and therefore become electrically grounded by their mechanical attachments to the mounting plate. Each variable capacitor has four solder lugs that are redundant "stator" terminals. On each capacitor, only one of these terminals is connected to V1A's and V6B's plate, respectively.

For safety, power supply components J3, F1, SW2, T1, T2, BR1, C30, C31, and R28 are fully enclosed in a 5" x 6" x 4" aluminum utility cabinet, separate from the main theremin assembly. J4 is an AC power inlet that mates with a 3-wire, grounded cord identical to the type used for most computers and test equipment. For construction simplicity, all the power supply parts are mounted to the inside surface of the utility cabinet's top panel, as illustrated in the Power Supply Lay-out drawing. Specific dimensions for the top panel are shown in the Power Supply Mounting Plate Hole Locations drawing. Note that the top panel is fabricated from 0.062"-thick aluminum, which replaces one of the two thinner, 0.040"-thick panels provided with the cabinet.

Adhesive-backed mounts and nylon cable ties are used to secure wires as required. The AC power inlet, fuse holder, switch, and transformer terminals are insulated with 1/8", 1/4, or 1/2"-diameter heat-shrink tubing, as required. Use the 1/2"-diameter tubing as an overall insulator for the rear of the fuse holder. Four self-adhesive feet are applied to the cabinet's bottom panel.

A four-wire extension cable with 9-pin "D" subminiature connectors connect the theremin assembly and power supply together. The length of the extension is optional, with about four feet being typical for extending from the floor to the top of a stand.

SAFETY NOTICES:  To prevent shock hazards from lethal mains voltage:

• Refer the power supply construction to a qualified electrician.
  
  
• Build the power supply in a separate, fully-enclosed cabinet.
  

• Do not defeat the grounding or fuse provisions shown in the schematics.
  
  
  
  
  
  
  
  
  
  
  

Test Voltages
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The following voltages are from the 126 theremin prototype, measured with a Tektronix type 485 oscilloscope, and a 10 Mohm, 10X-attenuation probe.
Due to variations in component tolerances, lay-out, and test conditions, user values may be different from those indicated

Unless otherwise noted:

1. A1 and A2 are substituted with 10 pF mica capacitors, connected from C4 and C15 to ground, respectively.
2. RV1 is adjusted fully clockwise.
3. V4 or V6 are removed for some steps to simplify measurements.

1. Adjust C5 for peak amplitude
2. Frequency determined by C24 adjustment
3. V6 removed
   
4. V4 removed
   
5. Value measured at the output jack with RV1 centered, and the pitch set with C24 at 440 Hz
6. Probe loading has a significant effect on these measured values.
   
   
   

-	TEST POINT	NOTE	VALUE
-
B+	BR1+	-	+45 VDC with less than 40 mV P-P of both 60 Hz and RF
-
V1A plate	V1-1	-	38 V P-P RF sine wave centered at +44.5 VDC
V1A grid	V1-2	-	0 V (ground)
V1A cathode	V1-3	-	10 V P-P RF sine wave centered at +2.7 VDC
V1B plate	V1-6	1	4.0 V P-P RF sine wave centered at +24.3 VDC
V1B grid	V1-7	1	1.6 V P-P RF sine wave centered at +2.9 VDC
V1B cathode	V1-8	1	1.1 V P-P RF sine wave centered at +2.5 VDC
-
V2A plate	V2-1	-	0 V (ground)
V2A grid	V2-2	-	0 V (ground)
V2A cathode	V2-3	1	4.3 V P-P RF sine wave with positive peak at +8 VDC, negative peak at -0.24 VDC
V2B plate	V2-6	1	4.3 V P-P RF sine wave with positive peak at +8 VDC, negative peak at -0.24 VDC
V2B grid	V2-7	1	4.3 V P-P RF sine wave with positive peak at +8 VDC, negative peak at -0.24 VDC
V2B cathode	V2-8	1	+ 4.5 VDC
-
V3A plate	V3-1	-	Refer to table at the beginning of this section
V3A grid	V3-2	2	Refer to table at the beginning of this section
V3A cathode	V3-3	-	Refer to table at the beginning of this section
V3B plate	V3-6	5	Refer to table at the beginning of this section
V3B grid	V3-7	-	Refer to table at the beginning of this section
V3B cathode	V3-8	-	Refer to table at the beginning of this section
V4A plate	V4-1	3	+44.9 VDC with less than 40 mV P-P of both 60 Hz and RF
V4A grid	V4-2	3, 6	6.5 VDC P-P RF sine wave centered at 0 V
V4A cathode	V4-3	3	3.7 VDC P-P RF sine wave centered at +2.1 VDC
V4B plate	V4-6	3	25 VDC P-P RF sine wave centered at +45.0 VDC
V4B grid	V4-7	3	0 V (ground)
V4B cathode	V4-8	3	3.6 V P-P RF sine wave centered at +3.3 VDC
-
V5A plate	V5-1	-	+44.9 VDC with less than 40 mV P-P of both 60 Hz and RF
V5A grid	V5-2	-	3.6 V P-P RF sine wave centered at +2.2 V
V5A cathode	V5-3	-	2.8 V P-P RF sine wave centered at +3.2 V
V5B plate	V5-6	2	0.7 V P-P audio wave with 100 mV RF modulation.
V5B grid	V5-7	-	3.5 V P-P RF sine wave centered at 0 V
V5B cathode	V5-8	-	2.7 V P-P heterodyne wave centered at +2.5 V
-
V6A plate	V6-1	4	+44.9 VDC with less than 40 mV P-P of both 60 Hz and RF
V6A grid	V6-2	4, 6	6.7 V P-P RF sine wave centered at 0 V
V6A cathode	V6-3	4	4.5 V P-P RF sine wave centered at +2.8 V
V6B plate	V6-6	4	29 V P-P RF sine wave centered at +44.5 V
V6B grid	V6-7	4	0 V (ground)
V6B cathode	V6-8	4	4.5 V P-P RF sine wave centered at +4 V

Photos
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These are two photos of the 126 Theremin prototype, courtesy of Jack Hertz.

Johannes Graenzer of Bayreuth, Germany constructed this 126 Theremin with monopole antennas for his university project. He reports that the instrument worked "immediately... and sounds nearly as good as C. Rockmore's if you play it by making a little vibrato..."

David Hunter of Toronto, Canada, built this 126 Theremin. The power supply is in the base, along with a speaker and amplifier.

Christopher Billey submitted this picture of his 126 Theremin. His version uses traditional antennas. It is his first vacuum tube theremin, and he reports that he is "very pleased with pitch range and sound quality."

Brendan Pope, an 18 year-old student from North Carolina, built this version of the 126 Theremin for his school project. It is the first theremin he has ever owned or built. Brendon relates "Its sound is supreme to any other homemade theremin I've heard."

Tomislav Ribicic of Croatia built this beautiful version of the 126 Theremin. The custom shellacked and waxed wood cabinet is topped by a stainless steel chassis plate. Traditional rod and loop antennas were used. Tomisalv reports that the theremin "sounds fabulous." He plans to install the instrument in the Caffe Jazz Tunel in Rijeka.

Yaroslav Sadovskiy of Moscow, Russia built this amazing version of the 126 Theremin. The six vacuum tubes are illuminated by LEDs, and the legends, laser cut into stainless steel plate, are likewise illuminated. Yaroslav reports good pitch sensing distance with the telescoping antenna, which also serves to fine-tune the theremin's zero in lieu of vernier capacitors. The wood sides add a "touch of vintageness," per Yaroslav, who also reports that the 126 "has the pure, classic theremin sound." The author is very pleased to have created this wonderful 126 in the city where Leon Theremin worked for a decade, at the Moscow Conservatory of Music.

Eric Reiswig from Canada built this excellent 126 Theremin with traditional loop and rod antennas fabricated from 3/8-inch diameter brass tubing. He incorporated the use of an IC reversing circuit to permit optional "closer-for-softer" volume response, and has expressed great satisfaction with the instrument's sound qualities.

Jeremy Merrill constructed this beautiful 126 Theremin in a wormy chestnut cabinet with a stainless steel chassis inset. He reports that the tone is excellent, and that his success has inspired him to build additional vacuum tube projects. The antennas are copper tubing, and the stand was adapted from a lamp.

This wonderful rendition of the 126 is named The Spheremin by its creator, Francesco Zuddas of Monfalcone, Italy. Francesco relates that two of his friends, both violinists, played the instrument, and found it to be amazing. Francesco used DC switching power supplies of 12 and 48VDC to power his design, with excellent results.

James Means produced this fine 126 Theremin and reports that it sounds "great through his Fender Twin Reverb amp." The enclosure is reclaimed wood from furniture drawers.

Guy Pasquet from the town of Joigny in the Burgandy region of France built this accurate version of the 126 Theremin. Guy is a veteran of electronics, born in 1927.

James Lafevre created this beautiful 126 theremin with spherical antennas. It utilizes the "Revision 3" volume circuit for either variation of volume detection.








Marc Bareille, from France, built this superb 126 theremin with rod and loop antennas, and reports that it has great fideltiy, great stability, and range. Marc has a webpage that describes his construction.









Bill Leake created this classical 126 theremin with particular attention to the article's exact recommendations, incorporating the revision 3 volume circuit.
He reports that the material cost (February, 2021) was about $700.
I have the pleasure of ongoing exchanges with Bill, who ran SPICE simulations for the instrument with a particular emphasis on the revision 3 volume circuit.









James Powell, a thereminist of many years, created this fascinating version of the 126 in a Sunbeam toaster enclosure.








Adam Mikolajczyk built his 126 theremin closely to specification, and reports great results. He incorporated breakaway hinges for internal
access or complete chassis removal, and mirror clips and PLEXIGLAS® to space the antennas away from the sides of the chassis.
Adam used stainless steel for the chassis plate, and a supplemental commercial enclosure. See his photo gallery of additional images..

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Parts Tables
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Table 1	Theremin Assembly (schematic-designated items)
Table 2	Power Supply Assembly (schematic-designated items)
Table 3	Theremin Assembly (hardware items)
Table 4	Power Supply Assembly (hardware items)
Table 5	Base Assembly
Table 6	Cable Assembly
Table 7	Fixture Items

• Suppliers indicated are not necessarily exclusive sources.

• A separate line item appears for each component in the assembly, and many common item types such as screws, nuts and washers
  appear on more than one line. † = item appears on more than one line.

• Table 7 indicates temporary items used to aid construction.

• A/R = as required

• NOTE 1:  Quantity 3, McMaster-Carr stock number 89015K37, provides enough material for both antennas, theremin mounting plate, and
  power supply mounting plate.
  

• NOTE 2:  The following manufacturers make transformers similar to the Signal Transformer Company types indicated in the table:
  Triad Magnetics: http://www.triadmagnetics.com/home.htm. Refer to their "Quick Pack" (TM) product line.
  Magnetic Coils, Inc.: http://www.mcitransformer.com/. Refer to their "Quick Connect Power Transformers" product line.
  Hammond Manufacturing: http://www.hammondmfg.com/. Refer to their "186/187" product line.
  

• NOTE 3:  Toko part number ##AHCFM2-455DL, specified in previous publications, is an acceptable substitute.

• NOTE 4:  A version of the filter is also available with strain-relieved wire leads attached, as Harrison Instruments item number 99999-5915-126X1-1.

• NOTE 5:  Where no cost value appears, the cost has been included in a previous line for the same type of item.
  To prevent ordering errors, the initial appearance of any particular type of item may include the total quantity required for the project.
  Builders are advised to review orders carefully to ensure that the correct quantities of each item are ordered.
  

• NOTE 6:  As a cost-saving measure, it is suggested that black 22 gauge hookup wire is used in substituiton of the other colors specified.
  Cost values for hookup wire other than black is therefore not indicated.

• NOTE 7: As a cost-saving measure, it is suggeted that the 16 gauge antenna lead-in bus wire is substituted with several twisted strands of the
  20 gauge bus wire (line 337). A cost value for 16 gauge bus wire is therefore not indicated.
  
  
  

Parts Table 1 ^
Theremin Assembly (schematic-designated items)

LINE	ITEM	DESCRIPTION	VALUE	MANUFACTURER	MANUFACTURER PART NUMBER	SUPPLIER	SUPPLIER STOCK NUMBER	QTY/ COST, USD (2 APR 2022)
101	A1,A2	ANTENNA (PER DRAWING) (SEE NOTE 1, ABOVE)	.	.	.	MCMASTER-CARR	89015K37	3† 68.46
102	C1, C14, C20, C23, C32	ELECTROLYTIC CAPACITOR	10 uF ±20%, 100 V, 105 °C, RADIAL, 6.3 mm D x 11 mm L	NICHICON	UPW2A100MED	MOUSER ELECTRONICS	647-UPW2A100MED	5 2.20
103	C2, C17, C26	MICA CAPACITOR	330 pF ±5%, 500 V	CORNELL DUBILIER	CD19FD331JO3	MOUSER ELECTRONICS	5982-19-500V330	3 11.34
104	C3	MICA CAPACITOR	100 pF ±5%, 500 V	CORNELL DUBILIER	CD15FD101JO3	MOUSER ELECTRONICS	5982-15-500V100	1 2.61
105	C4, C15	CERAMIC CAPACITOR	330 pF ±10%, X7R, 200 V, RADIAL	AVX	CK05BX331K	MOUSER ELECTRONICS	581-CK05BX331K	2 1.96
106	C5, C24	VARIABLE CAPACITOR	6.2-27 pF, 8:1 VERNIER	HARRISON INSTRUMENTS	99999- 5910-7-27R0	NO STOCK	99999-5910-7-27R0	2 52.50
107	C6	MICA CAPACITOR	10 pF ±5%, 500 V	CORNELL DUBILIER	CD10CD100DO3	MOUSER ELECTRONICS	5982-10-500V10	1 4.52
108	C7, C8, C21, C22	CERAMIC CAPACITOR	1000 pF ±10%, X7R, 200 V, RADIAL	AVX	C052C102K2R5TA7301	MOUSER ELECTRONICS	80-C052C102K2R5TA-TR	4 2.04
109	C9, C10, C11, C13, C18, C19, C27, C28, C29	METALIZED POLYESTER CAPACITOR	0.01 uF ±5%, 400 V, AXIAL	VISHAY/ ROEDERSTEIN	MKT1813310404	MOUSER ELECTRONICS	75-MKT1813310404	9 6.80
110	C12	ELECTROLYTIC CAPACITOR	100 uF ±20%, 100 V, 85 °C, RADIAL, 10 mm D x 20 mm L	NICHICON	647-UVR2A101MPD	MOUSER ELECTRONICS	647-UVR2A101MPD	1 0.78
111	C16, C25	MICA CAPACITOR	1000 pF ±5%, 500 V	CORNELL DUBILIER	CD19FD102JO3	MOUSER ELECTRONICS	5982-19-500V1000	2 8.00
112†	J1	CONNECTOR	9 POSITION, MALE CONTACTS, D-SUBMINIATURE	AMPHENOL FCI	DE09P064HTXLF	MOUSER ELECTRONICS	649-DE09P064HTXLF	1† 0.79
113	J2	PHONE JACK, WITH HARDWARE	1/4", INSULATED, MONOPHONIC	SWITCHCRAFT	N111X	MOUSER ELECTRONICS	502-N-111X	1 3.19
114	L1, L2, L3	INDUCTOR, THREE-SECTION, UNIVERSAL "PIE" WOUND	1 mH ±5%, 19 ohm Q = 59 @ 0.25MHz, SRF = 3.7MHz MINIMUM	J.W. MILLER	4652	NO STOCK	96804-4652	3 44.25
115	R1, R13 R18, R23	RESISTOR	5600 ohm ±5%, 1/2W, CARBON FILM	XICON	293-5.6K-RC	MOUSER ELECTRONICS	293-5.6K-RC	4 0.40
116	R2	RESISTOR	33.2 kohm ±1%, ±100PPM/°C 1/2W, METAL FILM	VISHAY BEYSCHLAG / DRALORIC / BC COMPONENTS	SFR25H0003322FR500	MOUSER ELECTRONICS	594-5053HD33K20F	1 0.19
117	R3, R30	RESISTOR	390 kohm ±5%, 1/2W, CARBON FILM	XICON	293-390K-RC	MOUSER ELECTRONICS	293-390K-RC	2 0.20
118	R4, R5, R7, R8, R12, R15 R17, R25	RESISTOR	1  Mohm ±5%, 1/2W, CARBON FILM	XICON	293-1M-RC	MOUSER ELECTRONICS	293-1M-RC	8 0.80
119	R6	RESISTOR	2000 ohm ±5%, 1/2W, CARBON FILM	XICON	293-2K-RC	MOUSER ELECTRONICS	293-2K-RC	1 0.10
120	R9, R10, R11, R32	RESISTOR	10 kohm ±5%, 1/2W, CARBON FILM	XICON	293-10K-RC	MOUSER ELECTRONICS	293-10K-RC	4 0.40
121	R14, R24	RESISTOR	39.2 kohm ±1%, ±100PPM/°C 1/2W, METAL FILM	VISHAY BEYSCHLAG / DRALORIC / BC COMPONENTS	SFR25H0003922FR500	MOUSER ELECTRONICS	594-5053HD39K20F	2 0.38
122	R16, R26, R27	RESISTOR	3900 ohm ±5%, 1/2W, CARBON FILM	XICON	293-3.9K-RC	MOUSER ELECTRONICS	293-3.9K-RC	3 0.30
123	R19	RESISTOR	100 kohm ±5%, 1/2W, CARBON FILM	XICON	293-100K-RC	MOUSER ELECTRONICS	293-100K-RC	1 0.10
124	R20, R21, R22, R31	RESISTOR	39 kohm ±5%, 1/2W, CARBON FILM	XICON	293-39K-RC	MOUSER ELECTRONICS	293-39K-RC	4 0.40
125	R29	RESISTOR	18 kohm ±5%, 1/2W, CARBON FILM	XICON	293-18K-RC	MOUSER ELECTRONICS	293-18K-RC	1 0.10
126	RV1	POTENTIOMETER, WITH HARDWARE	50 kohm ±20%, 0.25 WATT, CARBON COMPOSITION, AUDIO TAPER, WITH MOUNTING NUT AND FLAT WASHER	ALPHA	RV24AF-10- 15R1-A50K-3	MOUSER ELECTRONICS	31VJ405-F3	1 1.94
127†	SW1	SWITCH, TOGGLE, WITH HARDWARE	6 A, 250 V, SPDT	NKK	M2012SS1W01	MOUSER ELECTRONICS	633-M201201	1† 4.12
128	V1, V2, V3 V4, V5, V6	VACUUM TUBE, DUAL TRIODE	.	TESLA	ECC82	ANTIQUE ELECTRONICS SUPPLY	T-12AU7-JJ	6 99.60
129	X1	CERAMIC FILTER (SEE NOTE 3 AND NOTE 4, ABOVE)	UNLOADED fo = 462 kHz ±2 kHz, 3dB BDW = 10 kHz ±3 kHz, RIPPLE = 0 dB, MAX. INSERTION LOSS = 5 dB Zin = 3 kohm Zout = 3 kohm	MURATA SIGNAL CONDITIONING PRODUCTS	SFULA455KU2A-B0	NO STOCK	99999-5915-126X1	1 17.00

Parts Table 2 ^
Power Supply Assembly (schematic-designated items)

LINE			VALUE	MANUFACTURER	MANUFACTURER PART NUMBER	SUPPLIER	SUPPLIER STOCK NUMBER	QTY/ COST, USD (2 APR 2022)
201	BR1	RECTIFIER BRIDGE	6 A, 200 V	RECTRON	BR62	MOUSER ELECTRONICS	583-BR62	1 0.99
202	C30, C31	ELECTROLYTIC CAPACITOR	330 uF ±20%, 100 V, 85 °C, AXIAL, 13mm D x 31mm L	CDE / ILLINOIS CAPACITOR	337TTA100M	MOUSER ELECTRONICS	598-337TTA100M	2 6.34
203	F1	CARTRIDGE FUSE	1/8 A, 250 V, SLOW-ACTING, 0.25" D x 1.25" L	LITTELFUSE	576-0313.125MXP	MOUSER ELECTRONICS	576-0313.125MXP	1 2.82
204†	J3	CONNECTOR	9 POSITION, FEMALE CONTACTS, D-SUBMIN- IATURE	AMPHENOL FCI	DE09S064TLF	MOUSER ELECTRONICS	649-DE09S064TLF	1† 0.67
205	J4	AC POWER INLET	250 VAC, 15 A, CLASS 1	DGS PRO-AUDIO	161-0707-1-E	MOUSER ELECTRONICS	161-0707-1-E	1 1.04
206	R28	RESISTOR	100 ohm ±5%, 1/2 W, CARBON FILM	XICON	293-100-RC	MOUSER ELECTRONICS	293-100-RC	1 0.10
207†	SW2	SWITCH, TOGGLE, WITH HARDWARE	6 A, 250 V, SPDT	NKK	M2012SS1W01	MOUSER ELECTRONICS	633-M201201	1† 4.12
208	T1	TRANSFORMER (SEE NOTE 2, ABOVE)	PRIMARY: 120 V, 60Hz SECONDARY: 28 V, 85mA	BEL SIGNAL TRANSFORMER	241-3-28	MOUSER ELECTRONICS	530-241-3-28	1 12.39
209	T2	TRANSFORMER (SEE NOTE 2, ABOVE)	PRIMARY: 120 V, 60 Hz SECONDARY: 10 V, 1.2 A	BEL SIGNAL TRANSFORMER	241-5-10	MOUSER ELECTRONICS	530-241-5-10	1 14.69

Parts Table 3 ^
Theremin Assembly (hardware items)

LINE	ITEM	DESCRIPTION	MANUFACTURER	MANUFACTURER PART NUMBER	SUPPLIER	SUPPLIER STOCK NUMBER	QTY/ COST, USD (2 APR 2022)
301	THEREMIN MOUNTING PLATE	(PER DRAWING)	.	.	MCMASTER-CARR	89015K37	1†
302	STANDOFF, THEREMIN MOUNTING PLATE	6-32 x 1.25" L, HEXAGONAL, ALUMINUM	KEYSTONE	1818	MOUSER ELECTRONICS	534-1818	4 4.20
303	MACHINE SCREW, STANDOFF, THEREMIN MOUNTING PLATE	PAN HEAD, SLOTTED, 6-32 x 0.375", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A146 (PACKAGE OF 100)	4 6.52
304†	FLAT WASHER, STANDOFF, THEREMIN MOUNTING PLATE	#6, 0.312" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A314 (PACKAGE OF 250)	4† 14.84
305†	LOCK WASHER, STANDOFF, THEREMIN MOUNTING PLATE	#6 SPLIT-RING, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A540 (PACKAGE OF 100)	4† 1.78
306	BRACKET, OUTPUT JACK	(PER DRAWING)	.	.	MCMASTER-CARR	8199K13	1 33.01
307†	MACHINE SCREW, BRACKET, OUTPUT JACK	PAN HEAD, SLOTTED, 4-40 x 0.312", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A107 (PACKAGE OF 100)	2† 5.13
308†	FLAT WASHER, BRACKET, OUTPUT JACK	#4, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A309 (PACKAGE OF 500)	2† 15.57
309†	LOCK WASHER, BRACKET, OUTPUT JACK	#4 SPLIT-RING, 0.209 O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A530 (PACKAGE OF 100)	2† 1.83
310†	NUT, BRACKET, OUTPUT JACK	HEX, 4-40 x 0.250", STAINLESS STEEL	.	.	MCMASTER-CARR	91841A005 (PACKAGE OF 100)	2† 3.89
311	BRACKET, POWER CONNECTOR	(MODIFIED PER DRAWING)	KEYSTONE	621	MOUSER ELECTRONICS	534-621	2 0.84
312†	MACHINE SCREW, BRACKET, POWER CONNECTOR	PAN HEAD, SLOTTED, 4-40 x 0.250", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A106 (PACKAGE OF 100)	2† 4.79
313†	FLAT WASHER, BRACKET, POWER CONNECTOR	#4, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A309 (PACKAGE OF 500)	2† (NOTE 5)
314†	LOCK WASHER, BRACKET, POWER CONNECTOR	#4 SPLIT-RING, 0.209 O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A530 (PACKAGE OF 100)	2† (NOTE 5)
315†	JACK SCREW WITH HARDWARE, POWER CONNECTOR	4-40, 0.250" L STUD	KEYSTONE	.	MOUSER ELECTRONICS	534-7229	2† (NOTE 5)
316†	TERMINAL	INSULATED, SOLDER TURRET, 4-40 INTERNAL THREAD	WEARNES CAMBION	572-4814-01-05-16	BISCO INDUSTRIES	572-4814-01-05-16	53† 119.25
317†	MACHINE SCREW, TERMINAL	PAN HEAD, SLOTTED, 4-40 x 0.250", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A106 (PACKAGE OF 100)	49† (NOTE 5)
318†	FLAT WASHER, TERMINAL	#4, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A309 (PACKAGE OF 500)	49† (NOTE 5)
319†	LOCK WASHER, TERMINAL	#4 SPLIT-RING, 0.209 O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A530 (PACKAGE OF 100)	49† (NOTE 5)
320	SOCKET, TUBE	9-PIN, MINIATURE, WITH SHIELD RETAINER, 0.750" DIAMETER MTG HOLE, TOP-MOUNTED	BELTON	VT-9-ST-C	TUBE DEPOT	SK-B-VT9-ST-C	6 19.50
321†	MACHINE SCREW, TUBE SOCKET	PAN HEAD, SLOTTED, 4-40 x 0.312", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A107     (PACKAGE OF 100)	12† (NOTE 5)
322†	FLAT WASHER, TUBE SOCKET	#4, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A309 (PACKAGE OF 500)	12† (NOTE 5)
323†	LOCK WASHER, TUBE SOCKET	#4 SPLIT-RING, 0.209 O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A530 (PACKAGE OF 100)	12† (NOTE 5)
324†	NUT, TUBE SOCKET	HEX, 4-40 x 0.250", STAINLESS STEEL	.	.	MCMASTER-CARR	91841A005 (PACKAGE OF 100)	12† (NOTE 5)
325	MACHINE SCREW, VARIABLE CAPACITOR	PAN HEAD, SLOTTED, 6-32 x 0.250", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A144 (PACKAGE OF 100)	4 5.97
326†	FLAT WASHER, VARIABLE CAPACITOR	#6, 0.312" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A314 (PACKAGE OF 250)	4† (NOTE 5)
327†	LOCK WASHER, VARIABLE CAPACITOR	#6 SPLIT-RING, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A540   (PACKAGE OF 100)	4† (NOTE 5)
328	KNOB, WITH SET SCREW	25/32" D, 15/32" H, FOR 0.250" SHAFT, PHENOLIC, BLACK	DAVIES	1100	MOUSER ELECTRONICS	5164-1100	3 2.85
329†	LUG, GROUNDING	#4, INTERNAL TOOTH, 0.63" x 0.31"	KEYSTONE	908	MOUSER ELECTRONICS	534-908	2† 0.42
330†	MACHINE SCREW, LUG, GROUNDING	PAN HEAD, SLOTTED, 4-40 x 0.250", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A106 (PACKAGE OF 100)	1† (NOTE 5)
331†	FLAT WASHER, LUG, GROUNDING	#4, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A309 (PACKAGE OF 500)	1† (NOTE 5)
332†	NUT, LUG, GROUNDING	HEX, 4-40 x 0.250", STAINLESS STEEL	.	.	MCMASTER-CARR	91841A005 (PACKAGE OF 100)	1† (NOTE 5)
333†	WIRE, HOOKUP, DC RETURN	BLACK, 22 GAUGE, TEFLON® INSULATED, 100' ROLL	WEICO WIRE	M16878/4BFE-0	WEICO WIRE & CABLE	2122/19-BLACK (ROLL OF 100')	A/R† 140.46
334†	WIRE, HOOKUP, B+	RED, 22 GAUGE, TEFLON® INSULATED, 100' ROLL	WEICO WIRE	M16878/4BFE-2	WEICO WIRE & CABLE	2122/19-   RED (ROLL OF 100')	A/R† (NOTE 6)
335	WIRE, HOOKUP, SIGNAL	BLUE, 22 GAUGE, TEFLON® INSULATED, 100' ROLL	WEICO WIRE	M16878/4BFE-6	WEICO WIRE & CABLE	2122/19-   BLUE (ROLL OF 100')	A/R (NOTE 6)
336†	WIRE, HOOKUP, HEATER	GRAY, 22 GAUGE, TEFLON® INSULATED, 100' ROLL	WEICO WIRE	M16878/4BFE-8	WEICO WIRE & CABLE	2122/19-   GRAY (ROLL OF 100')	A/R† (NOTE 6)
337†	WIRE, BUS	20 GAUGE, TINNED COPPER, 100' ROLL	WEICO WIRE	9020	WEICO WIRE & CABLE	9020 (ROLL OF 100')	A/R† 42.61
338	WIRE, BUS, ANTENNA LEAD-IN	16 GAUGE, TINNED COPPER, 100' ROLL	WEICO WIRE	9016	WEICO WIRE & CABLE	9016 (ROLL OF 100')	A/R (NOTE 7)
339	SLEEVING, INSULATION	16 GAUGE, TEFLON®, 100' ROLL	ALLEN TECH	3DPTFE2/4CM5FT	AMAZON	B073RDFTDV (5' LENGTH)	A/R 196.06
340	LUG, ANTENNA	#6, INTERNAL TOOTH, 0.63" x 0.31"	KEYSTONE	914	MOUSER ELECTRONICS	534-914	2 0.42
341	WIRE TIE	NYLON, 3.9" L	PANDUIT	PLT1M-C	MOUSER ELECTRONICS	644-PLT1M-C (PACKAGE OF 100)	A/R 17.24
342	ANCHOR, WIRE TIE	NYLON, 1/2" SQ	PANDUIT	ABM1M-A-M	MOUSER ELECTRONICS	644-ABM1M-A-M	5 2.35

Parts Table 4 ^
Power Supply Assembly (hardware items)

LINE	ITEM	DESCRIPTION	MANUFACTURER	MANUFACTURER PART NUMBER	SUPPLIER	SUPPLIER STOCK NUMBER	QTY/ COST, USD (2 APR 2022)
401	POWER SUPPLY MOUNTING PLATE	(PER DRAWING)	.	.	MCMASTER-CARR	89015K37	1†
402	UTILITY CABINET, POWER SUPPLY, WITH HARDWARE	2-PANEL, ALUMINUM, 5" x 6" x 4"	BUD INDUSTRIES	AU-1029	MOUSER ELECTRONICS	563-AU-1029NF	1 23.10
403	FOOT, UTILITY CABINET	0.81" SQ x 0.3" H, SELF ADHESIVE, GRAY	3M	SJ-5023GY	MOUSER ELECTRONICS	517-SJ-5023GY	4 9.65
404	MACHINE SCREW, AC POWER INLET MOUNTING	FLAT HEAD, SLOTTED, 4-40 x 0.375", STAINLESS STEEL	.	.	MCMASTER-CARR	91781A108 FLAT HEAD (PACKAGE OF 100)	2 4.36
405†	NUT, AC POWER INLET MOUNTING	HEX, 4-40 X 0.250", STAINLESS STEEL	.	.	MCMASTER-CARR	91841A005 (PACKAGE OF 100)	2†
406†	FLAT WASHER, AC POWER INLET MOUNTING	#4, 0.250" 0.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A309 (PACKAGE OF 500)	2†
407†	LOCK WASHER, AC POWER INLET MOUNTING	#4 SPLIT-RING, 0.209" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A530 (PACKAGE OF 100)	2†
408†	LUG, GROUND	#4, INTERNAL TOOTH, 0.63" x 0.31"	KEYSTONE	908	MOUSER ELECTRONICS	534-908	1†
409†	MACHINE SCREW, LUG, GROUND	PAN HEAD, SLOTTED, 4-40 x 0.250", STAINLESS STEEL	. 0.25" D x 1.25" L	.	MCMASTER-CARR	91792A106 (PACKAGE OF 100)	1†
410†	FLAT WASHER, LUG, GROUND	#4, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A309 (PACKAGE OF 500)	1†
411†	NUT, LUG, GROUND	HEX, 4-40 x 0.250", STAINLESS STEEL	.	.	MCMASTER-CARR	91841A005 (PACKAGE OF 100)	1†
412†	MACHINE SCREW, TRANSFORMER	PAN HEAD, SLOTTED, 6-32 x 0.437", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A147 (PACKAGE OF 100)	4† 6.54
413†	FLAT WASHER, TRANSFORMER	#6, 0.312 O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A314 (PACKAGE OF 250)	4†
414†	LOCK WASHER, TRANSFORMER	#6 SPLIT-RING, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A540   (PACKAGE OF 100)	4†
415†	NUT, TRANSFORMER	HEX, 6-32 x 0.250", SMALL PATTERN, STAINLESS STEEL	.	.	MCMASTER-CARR	90730A007 (PACKAGE OF 100)	4† 5.98
416†	MACHINE SCREW, BRIDGE RECTIFIER	PAN HEAD, SLOTTED, 6-32 x 0.437", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A147 (PACKAGE OF 100)	1†
417†	FLAT WASHER, BRIDGE RECTIFIER	#6, 0.312" 0.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A314 (PACKAGE OF 250)	1†
418†	LOCK WASHER, BRIDGE RECTIFIER	#6 SPLIT-RING, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A540   (PACKAGE OF 100)	1†
419†	NUT, BRIDGE RECTIFIER	HEX, 6-32 x 0.250", SMALL PATTERN, STAINLESS STEEL	.	.	MCMASTER-CARR	90730A007 (PACKAGE OF 100)	1†
420†	TERMINAL	INSULATED, SOLDER TURRET, 4-40 INTERNAL THREAD	WEARNES CAMBION	572-4814-01-05-16	BISCO INDUSTRIES	572-4814-01-05-16	4†
421†	MACHINE SCREW, TERMINAL	PAN HEAD, SLOTTED, 4-40 x 0.250", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A106 (PACKAGE OF 100)	4†
422†	FLAT WASHER, TERMINAL	#4, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A309 (PACKAGE OF 500)	4†
423†	LOCK WASHER, TERMINAL	#4 SPLIT-RING, 0.209" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A530 (PACKAGE OF 100)	4†
424†	JACK SCREW WITH HARDWARE, POWER CONNECTOR	4-40, 0.250" L	KEYSTONE	7229	MOUSER ELECTRONICS	534-7229	2† 1.98
425†	WIRE, HOOKUP, TRANSFORMER PRIMARY LINE	BLACK, 22 GAUGE, TEFLON® INSULATED, 100' ROLL	WEICO WIRE	M16878/4BFE-0	WEICO WIRE & CABLE	2122/19-   BLACK (ROLL OF 100')	A/R† (NOTE 6)
426†	WIRE, HOOKUP, B+	RED, 22 GAUGE, TEFLON® INSULATED, 100' ROLL	WEICO WIRE	M16878/4BFE-2	WEICO WIRE & CABLE	2122/19-   RED (ROLL OF 100')	A/R† (NOTE 6)
427	WIRE, HOOKUP, B+ TRANSFORMER SECONDARY	YELLOW, 22 GAUGE, TEFLON® INSULATED, 100' ROLL	WEICO WIRE	M16878/4BFE-4	WEICO WIRE & CABLE	2122/19-   YELLOW (ROLL OF 100')	A/R (NOTE 6)
428	WIRE, HOOKUP, SAFETY GROUND	GREEN, 22 GAUGE, TEFLON® INSULATED, 100' ROLL	WEICO WIRE	M16878/4BFE-5	WEICO WIRE & CABLE	2122/19-   GREEN (ROLL OF 100')	A/R (NOTE 6)
429†	WIRE, HOOKUP, HEATER TRANSFORMER SECONDARY	GRAY, 22 GAUGE, TEFLON® INSULATED, 100' ROLL	WEICO WIRE	M16878/4BFE-8	WEICO WIRE & CABLE	2122/19-   GRAY (ROLL OF 100')	A/R† (NOTE 6)
430	WIRE, HOOKUP, TRANSFORMER PRIMARY NEUTRAL	WHITE, 22 GAUGE, TEFLON® INSULATED, 100' ROLL	WEICO WIRE	M16878/4BFE-9	WEICO WIRE & CABLE	2122/19-   WHITE (ROLL OF 100')	A/R (NOTE 6)
431†	WIRE, BUS	20 GAUGE, TINNED COPPER, 100' ROLL	WEICO WIRE	9020	WEICO WIRE & CABLE	9020	A/R†
432	TUBING, HEAT-SHRINKABLE	POLYOLEFIN, BLACK, 0.125"O.D., 48"	3M	FP301 1/8 BLACK	MOUSER ELECTRONICS	5174-1181 (4' LENGTH)	A/R 2.97
433	TUBING, HEAT-SHRINKABLE	POLYOLEFIN, BLACK, 0.250"O.D., 48"	3M	FP301 1/4 BLACK	MOUSER ELECTRONICS	5174-1141 (4' LENGTH)	A/R 3.23
434	TUBING, HEAT-SHRINKABLE	POLYOLEFIN, BLACK, 0.500"O.D., 48"	3M	FP301 1/2 BLACK	MOUSER ELECTRONICS	5174-1121 (4' LENGTH)	A/R 3.81
435	HOLDER, FUSE, FOR 0.25" D x 1.25" L FUSE	BK/HKP-R	BUSSMANN	BK/HKP-R	MOUSER ELECTRONICS	504-BK/HKP-R	1 9.40

Parts Table 5 ^
Base Assembly

LINE	ITEM	DESCRIPTION	MANUFACTURER	MANUFACTURER PART NUMBER	SUPPLIER	SUPPLIER STOCK NUMBER	QTY/ COST, USD (2 APR 2022)
501	BASE	(SEE NOTE 2, ABOVE)	.	.	.	.	1 14.99
502	STANDOFF, ANTENNA	6-32 x 0.500" L, HEXAGONAL, NYLON	KEYSTONE	1903C	MOUSER ELECTRONICS	534-1903C	8 6.40
503†	MACHINE SCREW, ANTENNA	PAN HEAD, SLOTTED, 6-32 x 0.312", STAINLESS STEEL	.	.	MCMASTER-CARR	91792A145 (PACKAGE 0F 100)	8†
504†	FLAT WASHER, ANTENNA	#6, 0.312" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	98019A314 (PACKAGE OF 250)	8†
505†	LOCK WASHER, ANTENNA	#6 SPLIT-RING, 0.250" O.D., STAINLESS STEEL	.	.	MCMASTER-CARR	92146A540   (PACKAGE OF 100)	8†
506	MACHINE SCREW, BASE	FLAT HEAD, SLOTTED, 6-32 x 0.625", STAINLESS STEEL	.	.	MCMASTER-CARR	91781A150 FLAT HEAD (PACKAGE OF 100)	12 6.36
507	ADAPTER, MICROPHONE STAND	1.75" O.D., 0.71" H, 5/8-27 INTERNAL THREAD	ATLAS SOUND	AD-11B	HARRISON INSTRUMENTS	99999-AD-11B	1 9.25
508	THREAD-FORMING SCREW, ADAPTER	PAN HEAD, TYPE A, PHILLIPS, #6 X 1/2", STAINLESS STEEL	.	.	MCMASTER-CARR	92470A148 (PACKAGE OF 100)	3 6.23

Parts Table 6 ^
Cable Assembly

LINE	ITEM	DESCRIPTION	VALUE	MANUFACTURER	MANUFACTURER PART NUMBER	SUPPLIER	SUPPLIER STOCK NUMBER	QTY/ COST, USD (2 APR 2022)
601	.	CABLE, 4-CONDUCTOR	4 22-GAUGE, 7 x 30 STRAND TINNED COPPER CONDUCTORS, PVC INSULATED, PVC JACKET, 0.185" O.D.	BELDEN	8444	SHOW ME CABLES	BELDEN 8444 (12')	A/R 21.84
602†	P1	CONNECTOR, 4-CONDUCTOR CABLE	9 POSITION, MALE CONTACTS, D-SUBMINIATURE	AMPHENOL FCI	DE09P064HTXLF	MOUSER ELECTRONICS	649-DE09P064HTXLF	1†
603†	P2	CONNECTOR, 4-CONDUCTOR CABLE	9 POSITION, FEMALE CONTACTS, D-SUBMINIATURE	AMPHENOL FCI	DE09S064TLF	MOUSER ELECTRONICS	649-DE09S064TLF	1†
604	.	MALE SCREW LOCK WITH "U" CLIP, CONNECTOR	4-40, 0.250" L	TYCO/AMP	5205980-3	MOUSER ELECTRONICS	571-5205980-3	2 2.02
605	.	HOOD, CONNECTOR	.	TYCO/AMP	207467-1	MOUSER ELECTRONICS	571-2074671	2 15.50
606	.	CORD, POWER	3 18-GAUGE, 41 x 34 STRAND CONDUCTORS, SVT JACKET, 10' L, SHIELDED	QUALTEK	312010-01	MOUSER ELECTRONICS	562-312010-01	1 9.87

Parts Table 7 ^
Fixture Items

LINE	ITEM	DESCRIPTION	VALUE	MANUFACTURER	MANUFACTURER PART NUMBER	SUPPLIER	SUPPLIER STOCK NUMBER	QTY/ COST, USD (2 APR 2022)
701	STANDOFF	6-32 x 2.5" L, HEXAGONAL, ALUMINUM	.	KEYSTONE	1825	MOUSER ELECTRONICS	534-1825	4 6.20
702	STANDOFF	6-32 x 2.0"L, HEXAGONAL, MALE/FEMALE, ALUMINUM	.	KEYSTONE	8425	MOUSER ELECTRONICS	534-8425	4 4.44

Total  items cost on April 2, 2022 (all tables) :  $1149.50

Drawing Index
(back to contents)

126 Theremin

Antenna

Brackets

Base

Component Locations

Insulated Solder Turret Terminal

Theremin Mounting Plate

Parameter Responses

Power Supply Lay-out

Power Supply Mounting Plate Hole Locations

Schematic (page 1)

Schematic (page 2)

Schematic (page 3)

Transformers

Text and drawings ©2002, 2003, 2005, 2008, 2010, 2013, 2014, 2015, 2017, 2019, 2020, 2021, 2022 by Arthur Harrison

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