Dis*Player Logo

General Information


Dis*Player is a precision electronic pitch display device, originally designed for my own use to assist in playing my theremin. Specifically, it is intended for PAiA Electronics' "Theremax" kit, but its design allows ready adaptation to other theremin designs, or for that matter, any other musical instrument allowing continuous pitch change. If constructed and adjusted as per the instructions, accuracy will be well within a quarter-tone over the five-octave total range.

Forty LEDs (Light-Emitting Diodes) are arranged in the traditional keyboard pattern, allowing a playable range of over three octaves. A three-position octave re-mapping switch extends the usable range to over five octaves.

Readily available parts are used throughout, and construction is non-critical. The project is well-suited for intermediate to advanced electronics experimenters.

This project appeared in the September, 1998 edition of Electronics Now magazine (a Gernsback publication, later replaced by Poptronics). The complete kits mentioned in the article are no longer available, but if there is sufficient interest I will contemplate making them available again.

The project may be built using "perf-board" and point-to-point wiring, or on a single- or double-sided printed circuit board (PCB). Artwork for the PCB, schematics, and parts lists are available for free downloading from the "Resources" section below. Alternately, a high-quality double-sided, plated-through manufactured PCB may be purchased directly from me. Click Here for further information.

Standalone Dis*Player
Prototype for the Electronics Now article,
set up as a standalone unit

Build your own Dis*Player
(Click on the link to view the technical article)


All the necessary files can be downloaded from the following table. The schematic and PCB artwork may be downloaded in high resolution GIF format, for printing to any 300 or 600 dpi printer. The parts list is available in Rich Text Format, and is also duplicated below.

The schematic and PCB artwork may be optionally downloaded at a medium resolution (fax quality) for a more manageable on-screen display. This version may also be superior for printing on certain printers because of the antialiasing and thicker circuit traces.

Note: if you're using the artwork files to create your own PCB, the final size of the PCB artwork should be exactly 2.52" by 9.57" (64 x 243 mm.) If you're using a viewer such as PaintShop Pro, you can specify the final dimensions directly. If you're using IrfanView, simply set the scale to 1.00 (for the hi-res images) or 2.50 (medium res) for both axes and do a test print; tweak the scale factors as required to end up with the proper dimensions. Similarly, best results will be obtained if you print the schematic file such that the final size will be 7" by 10" (178 x 254 mm).

The original HPG files are also available. If you happen to have a Hewlett-Packard laser printer (or other printer using the HPGL protocol), you can send these directly to the printer using the DOS "COPY /B [filename.hpg] LPT1" command. email me if you want me to send you these files.

  (Fax quality)
  Rich Text Format  
  Parts List N/A N/A disparts.rtf
  Schematic diagram dis_schl.gif dis_schm.gif N/A
  PCB Wiring side pcb_wire.gif pcb_wi-m.gif N/A
  PCB Component side pcb_comp.gif pcb_co-m.gif N/A
  PCB Silkscreen layout pcb_silk.gif pcb_si-m.gif N/A
  Octavizer schematic tmax-f2l.gif tmax-f2s.gif N/A

I also suggest that you print out the technical article for reference during assembly, unless you happen to have your soldering iron next to your computer. :) If you're planning on implementing the "Octavizer" or other modifications to Theremax, print out this page also.

©1997 Fred Nachbaur

CAPACITORS: (+20 -10% tolerance unless noted)
Low note: A=110
C1, C2, C6, C12-C192.2 µF 16V tantalum
C33300 pF ceramic
C44.7 µF 16V electrolytic
C510 µF 16V electrolytic
C7C20, C21 - 0.01 µF disc ceramic
C80.02 µF mylar, 5%(0.01 µF)
C90.47 µF 16V electrolytic or tantalum(0.22 µF)
C10, C220.10 µF mylar or ceramic(0.05 µF)
C110.20 µF mylar or ceramic(0.10 µF)
C231000 pF ceramic
C24470 pF ceramic

D1, D21N4148, 1N914 or equivalent

IC17805 positive regulator, TO220
IC2NE555 or TLC555 timer
IC3LM311N comparator
IC4DM4027 or MC14027 dual J-K flipflop
IC5LM2917N F-V converter (14-pin version)
IC6LF353, TL062, or TL082 dual op amp, FET input
IC6-IC11LM3914 LED linear display drivers
IC1279L05 negative regulator, TO92

J1Hollow pin jack, 2.1 mm.
J2, J31/4 mono phone jack

LED1-LED3small green LEDs
LED4-LED6small yellow or orange LEDs
LED7-LED10small red LEDs
LED11, 13, 14, 16, 18, 19, 21, 23, 25, 26, 28,
30, 31, 33, 35, 37, 38, 40, 42, 43, 45, 47. and 49
large red LEDs
LED12, 15, 17, 20, 22, 24, 27, 29, 32. 34, 36,
39, 41, 44, 46, and 48
large green LEDs
LED 50 (optional)large orange or yellow LED

Q1,Q22N3904. 2N4401, 2N2222 or similar NPN signal transistors
(from same production run)

RESISTORS (all 1/4W, 5% metal film):
R124K (K=1000; i.e. 24K = 24000 ohms)
R3, R3922K
R4, R5, R8, R9 ,R12 ,R13 ,R19100K
R14, R174.7K
R6, R10, R24, R27, R30, R33-R3710K
R11470 ohm
R15, R1847K
R21750 ohm
R22, R25, R28, R3120K
R29, R323K
R404.7 Megohm

RV1-RV450K linear trimpots (layout is
for Bourns 3329-H-1-503 or equivalent)

SW12-pole, 3-position rotary switch
(or 3-pole, 4-position for power switching)
SW2 (optional)SPST power on-off switch

single- or double-sided PC board
jumper wire (single-sided board) or feedthrough wire (double-sided board)
mounting hardware
hookup wire
12 volt DC, 200 mA. (or better) power supply
cables to instrument

Most if not all parts are available from any electronics jobber. If you are not near a larger centre with a suitable electronics store, check with Mouser, Active Electronics, Newark or Electrosonic (Canada). Additional sources are listed at the Poptronics site.

Assembled Dis*Player Board
Fully assembled Dis*Player board


A number of commercially-produced bare Printed-Circuit Boards are still available. These are manufactured from high-quality glass-epoxy material, double-sided with plated through holes. The component side is silk-screened with the component layout for ease of assembly. The few components that mount onto pads on the wiring side are indicated also. Circuit traces are tin-plated for protection and ease of soldering.

Email me for details
Bare Board, wiring side
Wiring side of bare PCB

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---This page last updated Apr. 18, 2002.
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