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Page Update
08/22/08
Close Up
(880K)
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RS
Illusion Theremin
A Modified Ult-2c
Perfect Pitch Linearity, Null point
breaks about 24" outside
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Click here for the RS Illusion Schematic drawn
by Don Parrish-Bell
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New
L2 Oscillator Board
These changes are for the RS Illusion
before 8.09.08 and all Ultimate 2c boards.
Replace R9 with the
7805 5 volt regulator (metal
plate side away from the board).
Use 9 volt power instead of 6 volts. Total circuit current
using the 7805 is 10 ma.
@ 9 volts.
Change C3 to
.22uf and R15 to a D8 1N914 diode
"stripe" towards LED 1
Change R18-470 to 1K and R19 220
to 470 ohms.
Remove the D3 zener
diode, C17-100uf and the L2
self wound coil.
Parts
below no longer used on pc board but no need to
remove them.
Q2,C8,C9,C12,D6,D7,R5,R6,R7,R20,R21
L2 connections -
DW,
Ground & +V2 shown with
O. Use
6" to 12" of twisted wire. |
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RS
Illusion
a modified Ultimate 2c
* The 07.12.08 board error (need emitter wire at Q2) has been fixed on the
revised 07.23.08 board PDF.
* Changed R19 from 100 ohm to 220 ohm so current at 9
volts does not damage mini Pot 2 7.12.08
* Added the yellow Coil Coupling wire
in photo above, it helps the coils interact for a good sine wave
shape.
* Added to the Audio Out capacitor C20-4.7uf which is a non-polarized electrolytic.
7.10.08
* Added switch pads S2 to turn LED 2
on/off, the pads are normally connected on the copper
clad side.
* Added R21-100K & R20-100K in parallel with diodes
D6 & D7. Part of TW demodulator.
7.10.08
* Changed C3 from 100pf to .001 uf, you should have this
from the pack of two. 7.10.08
* Moved location of R7, this does not effect anything.
7.10.08
* Changed R11 from 470 ohms to 4.7K for less gain in the
second OP Amp of U2. 7-08-08
*
Added a second set of board pads to move coils L1-A
& L1-B farther apart. 7-04-08
* Re-numbered the Coil pad silkscreen markings &
modified the schematic for clearer coil orientation.
* Removed Ult-2c D5 and replaced R20-10K with R15-470
ohm for increased square wave influence on the
sound.
* Used diode D5 near the Power (battery) to protect against accidental reversed polarity.
* Changed C10-10 uf capacitor with a 1000 uf cap. and gave it room
near the IC's. (this dampens LED-1 pulsing)
* R10 and the big square pads are not used currently. |
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Ultimate
2c
a modified Ultimate 2b Note:
If you already built the Ultimate 2c study the
modifications above.
* Added the Tickle Wire for improved oscillator
coupling.
* Added R9 470 ohms and Zener D3 for oscillator circuit
voltage regulation.
* Replaced
homemade Coil L1 with two ferrite chokes (This added two
more linear octaves in the pitch field.)
* Replace PVC coil form with salt cardboard form for a
cleaner sound.
* Added D5 to soften square wave effect to Pot 3. (I
didn't like this Mod, it is to soft.)
* The white line is a jumper wire you need if you didn't
use Pot 3 on the board.
* C3 .1 uf becomes C17 100 uf part of the voltage
regulation.
* C15 10 uf at Pot 1 changes to 4.7 uf for less low
frequency roll off.
* Added pads for sqr & gd off of pin 3 of the
TLC555. (Not used at this time.) The Radio Shack #273-1374 1:1 isolation transformer
may be needed on the TLC555 square wave output (sqr & gnd) to keep the TLC555 special ground isolated from the main ground.
Unless you're really into
experimenting you will never use the 555 square wave output connection. |
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Limited
by what parts I could find at Radio Shack my bread boarding
evolved into a remarkable theremin!
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The
first 100% Radio Shack theremin using two AM Radio kits.
2003
This thing had {{{horrible}}} temperature drift and it
sounded like a mouse on helium!
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| The
humble beginning of the RS Theremin 2003
I
thought I would place capacitive plates on opposite sides of the
black triangular case, at this time I believed in the hand capacitance
theory because it seemed everyone said. . . this is how it
works.
"I
was in for a surprise, the whisper. . ."
Read My
Observations
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