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Theremax
Since it's introduction to the general public in the late '20s, the Theremin
musician producing sound using only a conductor's gestures. And it's pure
tones, able to stand out without distortion against even the full fortissimo of
a symphony orchestra, were like nothing anyone had ever heard before.
audiences were ordinarily sparse. The place of the Theremin in a "mod-
ern" orchestra was a given for such maestros as Leopold Stokowski, who
used one or more in numerous concerts of the Philadelphia Orchestra
Theremins and produces the classic sound while adding embellishments
made possible by the economy of transistors and Integrated Circuits. It
can function as a stand-alone instrument or as a gesture-sensing control-
062702
has been evocative in image and tone. Even eyes that had seen such
wonders as pictures flying through the air widened at the sight of a
Was it a hit? You bet, theremin concerts were SRO in halls where
during the late '30s. RCA thought that every cultured home would have
one, but for a lot of reasons things didn't work out quite like that.
Theremax employs the same heterodyneing principles as the original
ler for other musical instruments or in performance art applications.
(c) 1996 PAiA Electronics, Inc.
Portions of this document are excerpted from
an article appearing in the Feb 1996 issue of
Electronics Now magazine, copyright 1996,
and are reprinted by permission of the Publisher.
Model 9505
Assembly and Using Manual
Theremax
1

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Summary of Contents for Paia Theremax 9505

  • Page 1 (c) 1996 PAiA Electronics, Inc. Portions of this document are excerpted from an article appearing in the Feb 1996 issue of Electronics Now magazine, copyright 1996, and are reprinted by permission of the Publisher.
  • Page 2 ASSEMBLING THEREMAX Before beginning assembly, go through the manual. Look at the drawings. Feel the parts. You’re naturally eager to plunge right in, but take a few deep breaths first. Notice that each step in the manual is marked with a checkoff box like this: DESIGNATION VALUE...
  • Page 3: Tips From The Pros

    use the magnifier to examine each solder joint as it is made to make sure that it doesn’t have any of the problems described in the SOLDERING section which follows. SOLDERING Select a soldering iron with a small tip and a power rating not more than 35 watts.
  • Page 4: Wire Jumpers

    WIRE JUMPERS Assembly begins by forming and installing the eight wire jumpers indicated by bold lines on the circuit board parts placement designators and numbered in the illustration to the right. For each jumper, cut a length of the bare wire supplied by measuring it against the distance between the circuit board holes and adding about 1/2".
  • Page 5 DESIGNATION VALUE COLOR CODE A-B-C ( ) R1 brown-black-brown ( ) R22 1000 brown-black-red ( ) R23 1000 brown-black-red ( ) R56 1000 brown-black-red listed below: 100k brown-black-yellow ( ) R71 ( ) R72 ( ) R73 ( ) R74 listed below: brown-black-orange ( ) R11...
  • Page 6 DESIGNATION VALUE COLOR CODE A-B-C ( ) R28 yellow-violet-brown ( ) R67 yellow-violet-brown ( ) R68 yellow-violet-brown ( ) R26 4700 yellow-violet-red ( ) R45 4700 yellow-violet-red ( ) R59 4700 yellow-violet-red listed below: 470k yellow-violet-yellow ( ) R27 ( ) R29 ( ) R40 ( ) R60 listed below:...
  • Page 7 CERAMIC DISK AND MYLAR CAPACITORS Many of the capacitors used in Theremax are nonpolarized Ceramic Disk and Mylar types. For all of these, either lead can go in either of the holes in the circuit board. The leads of the Ceramic Disk and Mylar capacitors are already parallel to each other but still may need to be bent slightly to match the spacing of the circuit board...
  • Page 8: Electrolytic Capacitors

    DESIGNATION VALUE MARKING listed below: 220pF ( ) C22 ( ) C27 ( ) C34 ( ) C37 33pF listed below: 470pF ( ) C7 ( ) C11 ( ) C15 ( ) C19 ( ) C28 ( ) C31 NPO Ceramic Disks ( ) C6 100pF NPO...
  • Page 9 DESIGNATION VALUE ( ) C21 10uF 10V ( ) C26 10uF 10V listed below: 1uF 10V ( ) C23 ( ) C32 ( ) C35 ( ) C36 ( ) C38 ( ) C29 4.7uF 10V DIODES Three types of diodes are used in Theremax, five 1N914 / 4148 silicon signal diodes in small transparent glass cases, one zener diode also in a small transparent case and four 1N34A germanium...
  • Page 10: Integrated Circuits

    DESIGNATION TYPE listed below: 1N914 or 1N4148 Silicon Diode ( ) D10 ( ) D11 ( ) D12 ( ) D13 ( ) D14 INTEGRATED CIRCUITS Of all the parts, the ICs are the most easily damaged and should be treated with some respect. In particular, they may be destroyed by discharges of static electricity.
  • Page 11 TRANSISTORS Install the transistors by inserting their three leads through the holes provided for them in the circuit board. Note that the transistors are polarized by the flat side of the case. When the transistors are properly installed this flat will align with the corresponding mark on the circuit board legending.
  • Page 12: Shielded Cable

    SHIELDED CABLE RG-174/U coaxial cable is used to make shielded connections between the circuit board and the antennae. Make two equal length cable sections by cutting the single piece supplied in half. Prepare the ends of the two pieces as follows: Strip 1/2"...
  • Page 13: Panel Controls

    We can now put the circuit board assembly aside while we do some pre-wiring to the Control Panel. This would be a good time to check your work on the circuit board to this point. Make sure polarized components are placed properly and be critical of all your soldering joints.
  • Page 14 Now we'll do some preliminary wiring on the Control Panel parts as shown in fig 3. Notice that individual solder lugs are identi- fied by part number and lug designation. For example R79-1 means the lug labeled "1" of the Potentiometer R79. Jack lugs are designated "T"...
  • Page 15: Color Code

    FROM LENGTH ( ) R83-2 (s1) J5-T (ns) 10-3/4" ( ) R84-2 (s1) J3-T (ns) 4-1/4" ( ) R82-2 (s1) J4-T (s1) 2-3/4" ( ) R84-1 (s2) J6-S(s1) 10-1/2" Four resistors are mounted directly on the solder lugs of the potentiometers and jacks.
  • Page 16: Case Assembly

    ( ) Push the lens of LED D16 through the hole provided for it in the control panel as shown in fig 3. Connect the free end of R77 to lug #3 of S1 as shown. DO NOT SOLDER this connection yet. ( ) Prepare a 10"...
  • Page 17 ( ) Begin Case assembly by attaching the end panels to the front and back panels using the eight #6 X 1" Flat Head wood screws provided. The Front Panel is designed to be completely symmetrical and can be mounted with either surface to the front and either edge to the top. The Back panel is not symmetrical and must be mounted with the curved edge up and the curve facing into the box.
  • Page 18 ( ) Strip 1/4" of insulation from the end of the (+) Power Supply wire and twist and tin the exposed wire strands. Connect this wire to lug #1 of Power Switch S1 mounted on the control panel. Solder the single wire at this lug (see fig 4). ( ) Attach the Theremax circuit board to the case bottom using the four 4-40 X 1/2"...
  • Page 19 ( ) Mount the Pitch and Volume antennae using #10 X 1" OD Flat Washers and #8 Wing Nuts as shown in the illustration. Note that the Vertical Pitch Antenna mounts on the right and the loop-shaped Volume antenna on the left. Each antenna mounts by slipping the end without the mounting loop through the hole in the end panel from the inside of the case.
  • Page 20 Tuning and Testing First time tuning can be tricky because both the Pitch pair and Volume pair of oscillators must be close to a null in order to hear anything at all. If the Pitch pair are close, but the Volume pair are far apart you won’t hear anything because the Volume doesn’t come on.
  • Page 21 others. The point at which the frequency of these louder tones go through zero is the ideal setting. But don’t confuse this null point with the two super-audio regions when the slug is a little too far “out” or “in”. You won’t be able to set exact null by tuning L2 unless it’s by random chance.
  • Page 22 pressed” so that all the change in Volume happens over only a few inches of hand motion, try turning L3’s slug just slightly CCW, about 1/16 turn. This will produce a slightly lower overall output, which should be compensated by turning up the amplifier’s gain control.
  • Page 23 ( ) Attach the self adhesive rubber feet to the case bottom corners by removing the protective backing and sticking them in place. USING THEREMAX Playing the theremin is an art that can't be taught in a few paragraphs. Still, plunging ahead where much wiser men fear to tread, here are some observations on the playing style of Clara Rockmore.
  • Page 24 In some circles Voltage Controlled analog music synthesizers, antiques that they are, have great cachet . Theremax makes a useful supplemental or alternate controller to the keyboards typically used in these instruments. The figure above shows only one of an unlimited number of possible "patches".
  • Page 25 DESIGN ANALYSIS The complete Theremax schematic is shown in Fig 6. At the heart of the circuitry are four oscillators, two of which are mixed to produce the pitch signal and two of which are mixed to produce the volume control signal. If it occurs to you that one oscillator could serve as refer- ence for both pitch and volume sensing you have a good designer’s instincts, this would be more economical.
  • Page 26 For both pitch and volume, the outputs of the reference and sensing oscillators are taken off of the secondaries of their respective inductors to buffer them from the effects of loading by the rest of the circuitry. Taking the pitch circuitry as typical, the oscillators are mixed in the modulator consisting of D3 and D5.
  • Page 27 The Volume CV is also used to derive a Velocity Control Voltage. Natural instruments are sensitive to how hard you play them and in this MIDI age this quality has come to be know as Velocity . In Theremax, Velocity is proportional to the rate of increase of Volume, the “velocity” with which you hand is approaching the Volume Antenna.
  • Page 28 Theremax Parts List Semiconductors 8.2V 400 mW. Zener Diode Quan Desc Designation 1N34A or 1N270 Ge Diode D3,D5,D7,D9 Capacitors 1N914 / 4148 Si Diode D10-D14 Ceramic disk Red LED *D15,*D16 .001uF C40,C41 LM339 Quad Comparator .0047uF C39,C44 748 OpAmp .01uF C2,C4,C8,C12, 2N4124 NPN Transistor Q1-Q12...

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