About: A retired electronics engineer -motorola. delveing into new craft ideas and contest entries.

Introduction -- Make a device with standard electronic parts to generate a tremolo effect in any instrument that has an output jack to an amplifier and /or wireless interface such as a standard FM receiver; the effect also can sound like an echo effect with the adjustable controls.

Step 1: Parts

The parts are listed above. They were purchased from Radio Shack,Jameco and locally.

The parts are assembled in an aluminum box approximately 2x3x5 in.

The box top can be painted white if you wish, as shown here.

The voltage source is a 9 volt battery enclosed in the box. .

The method used here requires CdS light dependent resistors .The critical part here is that the resistor have a minimum resistance of 500 ohms when light actuated.Led used to light them.

The second method of circuit chopping for tremolo effects is a mini-reed that is incorporated here if you want to use it.

The 555 timer is standard low cost 8 pin IC.

Wire--Ribbon cable wire is used here or any you have on hand.

resistors- smallest you can find 1/8 to 1/4 watt.

capacitors wide tolerance, low operating voltage, small size needed.

potentiometers are low cost , small sized, low wattage.

LEDs- standard types 1/4 diameter, red. or amber. output.10. maDC. A third LED can be used at the pin 3 of 555 to indicate rate output when varying the two Pots time base.

Connectors- low cost types that are panel mount. momo and stereo are used.

Step 2: Case Assembly

See diagram. case to be assembled as shown.

The mechanical layout is not critical. The switches are placed in the as needed locations..depending on the type of attachment the switch has.

s-1 on off and a LED power light.

s2 selector a- Photoresistor chopper is used for mellow effects. b- a deep sharp chopper is used with a mini- reed.

A third led can be added between the 2 pots showing the rate of output.Not shown above} .connect positive of led to pin 3 of 555 timer and a 470 ohm series resistor to ground.

S3- switch is to select the tremolo or if one wants to see how the music sounds without the tremolo effects.

See wiring diagram from pc board to switches and connectors.and plugs.

Step 3: Wiring of Board.

See circuit diagram under Parts..

pc board. or use a perfboard that is available.. The photo resistor is mounted about 1/4 inch from the Led. The parts can be covered so external light wont give a false readout of about 500 ohms when led is lit and about 10k ohms when dark. When the cover is added there is sufficient darkness however.

Battery mount can be any bracket available. or allow to float.

connectors and cables- standard wiring.

Pots- cut rods to length for knobs.

555- can be direct wire or as we have here a 8 pin socket is used.

Step 4: Wiring in Case and Test..

wire- use any awg 22 wire. we use ribbon cabe wire.

Test- Use any radio output and feed into the Input. Select music is best.

Turn power on. then S3 to tremolo On. S2 selects Optical and Reed relay method of chopping the signal.

also test-.

output- S3- Tremolo off or on. If OFF then only signal goes thru without tremolo..

connect output to a cable to a amplifier and loudspeaker. There should be a echo tremolo effect . It can be varied by adjusting the Pot 1 and Pot 2. some experimenting is necessary here.

Led 3 can be used to see how much on/off rate is being generated. square wave output t1 and t2. It flikers.

Output can also be a wireless mike connecting via radio waves to a distant FM set . The wireless mike used here on my lyre was found in Amazon internet. for 6 dollars. Transmitted at 107.Mhz. worked fine.

A headphone ear piece was placed in my Lyre also feeding into my pre-amplified stereo amplifier and performed nicely as a low cost microphone.

Time to construct-- 40 hours.

Cost- approx.$20.

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