MUTE FEATURE ADDITION FOR THE BIG BRIAR ETHERWAVE® THEREMIN
(A newer version of this circuit is here.)


DESCRIPTION: This circuit permits the addition of a "mute" switch to the Etherwave® Theremin, useful for placing the theremin in a silent mode without having to turn it off completely. There is no "pop" during the mute-unmute transition. A MUTE STATUS light-emitting diode doubles as a convenient power indicator.

The circuit was constructed on a small circuit board installed inside the theremin. The MUTE CONTROL switch and MUTE STATUS light-emitting diode were mounted on the front panel, near the output jack.

CIRCUIT DESCRIPTION: U1 is a six-section logic inverter. Sections A and B and associated components form a bistable circuit which alternately provides a 0 volt or -12 volt level with each momentary actuation of switch S1. U1B-4's output drives a LED control circuit comprised of U1C through F. LED1 illuminates red when the theremin is muted, and green when it is unmuted. R5 is the LED current-limiting resistor. R2 protects U1A's input from static transients.

U1B-4's output also drives transistor Q1, that translates the levels into -16 volts and 0 volts, controlling the gate of N-channel junction field-effect transistor Q2 via the R6-C3 integrator.

Q2's drain-source circuit is connected in parallel with the instrument's voltage-controlled amplifier control input. Q2 pulls the control input of the theremin's VCA  (U3) to -12V for full muting and opens for unmuted operation. R6 and C3 provides a controlled rate of transition between the two modes to prevent "pops" in the audio output.




REVISIONS

DATE

REV. NR

DESCRIPTION

6 April 1998

Release

-

7 April 1998

001

Change Q2 from 2N3819 to 2N5484 with VGS(off) specification of -3 volts to ensure operation under low unregulated negative supply conditions.



PARTS TABLE

ITEM

DESCRIPTION

VALUE

MANUFACTURER

MANUFACTURER PART NUMBER

SUPPLIER

SUPPLIER CATALOG NUMBER

QTY

C1 CAPACITOR, TANTALUM 1 uF KEMET T350A105K035AS DIGI-KEY 399-1429-ND 1
C2,3 CAPACITOR,CERAMIC 1 uF KEMET C330C105K5R5TA DIGI-KEY 399-4389-ND 2
LED1 LIGHT-EMITTING DIODE RED/GREEN LITE-ON LTL-293SJW DIGI-KEY 160-1038-ND 1
Q1 TRANSISTOR PNP BIPOLAR FAIRCHILD SEMICONDUCTOR 2N3906 DIGI-KEY 2N3906FS-ND 1
Q2 TRANSISTOR N-CHANNEL JFET FAIRCHILD SEMICONDUCTOR 2N5484 MOUSER 512-2N5484 1
R1, 5 RESISTOR 10K OHM, ±5%, 1/4 WATT YAGEO CFR-25JB-10K DIGI-KEY 10KQBK-ND 2
R2, 7 RESISTOR 1K OHM, ±5%, 1/4 WATT YAGEO CFR-25JB-1K0 DIGI-KEY 1.0KQBK-ND 2
R3, 4 RESISTOR 100K OHM, ±5%, 1/4 WATT YAGEO CFR-25JB-100K DIGI-KEY 100KQBK-ND 2
R6 RESISTOR 220K OHM, ±5%, 1/4 WATT YAGEO CFR-25JB-220K DIGI-KEY 220KQBK-ND 1
S1 SWITCH SPDT MOMENTARY C & K 8125SHZBE DIGI-KEY CKN4022-ND 1
U1 INTEGRATED CIRCUIT CMOS HEX INVERTER TEXAS INSTRUMENTS CD4069UBE DIGI-KEY 296-3518-5-ND 1

Note:  Only major items are indicated in the Table. Items such as wire, terminals, circuit board, and fasteners are not shown.



April 6, 1998

Text and images ©1998 by Arthur Harrison


Back to the Circuit Library Index

Back to the Opening Page of Art's Theremin Page