The document outlines a project to build a plasma speaker to amplify electric guitar sound. It describes constructing an audio oscillator circuit to test speaker performance, then replacing the speaker with an ignition coil to create a plasma arc. Frequency and duty cycle measurements from the circuit are provided and compared to calculated values. The goal of creating a plasma-powered guitar amplifier is also discussed.

1. JOE GROELE

2. Project Outline
The goal of this project was to build a plasma
speaker that will amplify an electric guitar
sound.
 Build an audio oscillator circuit using an
ordinary speaker
 Test speaker performance compared to
equations on data sheet
 Replace speaker with auto ignition coil to
create a plasma arc
 Replace audio oscillator with an Audio
Power Amplifier

3. Hypothesis
I hypothesize that an Audio Power
Amplifier will be capable of magnifying
the output of an electric guitar through a
plasma arc.
The values of the measured frequency and
duty cycle will match the equations on
the data sheet for the oscillator circuit if
built correctly.

4. Materials



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








Solder
Soldering iron
Wire
Wire strippers
Wire Cutters
Multimeter
Oscilloscope
Electronic tuner
Perf board
Auto spark ignition
Connector terminal
Power connector
Guitar input jack












Eight pin DIP socket
0.01 µF capacitor
0.1 µF capacitor
10 ohm resistor
330 ohm resistor
100 ohm resistor
1 K ohm resistor
10 K ohm potentiometer
IRF510 MOSFET
transistor
P2N2222 transistor
ICM7555 CMOS timer
LM386 audio power
amplifier

5. Constructing the Audio Oscillator
Circuit
Create the audio oscillator using the
ICM7555 CMOS timer following the product
data sheet
 Add amplifying transistors from example
circuit

Example circuit from: http://geocities.com/CapeCanaveral/Lab/5322/fbt2.htm

6. Audio Oscillator Circuit Diagram
9V
POT1
10K
RESISTOR
1K
SPEAKER
RESISTOR
330
POT1
10K
NMOS
7
8
4
RESISTOR
NPN
ICM7555
RESISTOR
1K
2
C
0.1 or 0.01
GND
6
1
RESISTOR
10
3
100
IRF510
2N2222

7. Testing the Audio Oscillator
Circuit
Connect speaker to the output
 Attach a 9 Volt battery
 Frequency and duty cycle are changed by
adjusting the two potentiometers and the
value of the capacitor
 Take measurements of frequency and duty
cycle using an oscilloscope and an electronic
tuner
 Compare to calculated values


8. Frequency and Duty Cycle
Connect oscilloscope
and take measurements,
T1 and T2
 Use ohm meter to
measure RA and RB
 Adjust potentiometers
and repeat
measurements

Measured:
F
1
T2
T1
T2
Calculated:
D
T1
T2
F
1.38
( RA 2 RB )C
D
R A RB
RA 2 RB

9. Creating a Plasma Speaker








Replace speaker with auto ignition coil
Connect wires from the primary coil to the circuit
board
Attach wires to the secondary high voltage coil
Adjust spacing between wires to create a small gap 2 to 5mm worked best
When the circuit is energized, the air between the
electrodes is ionized and becomes a plasma
A new spark is created with every oscillation of the
circuit
Your ear hears this as a musical tone
The frequency or note of the tone can be adjusted
using the potentiometers

10. Creating the Plasma Powered
Guitar Amp
A second copy of the circuit was constructed, replacing the
oscillator chip with a low voltage audio power amplifier
 The gain of the amplifier was increased to 200, which gives a
square shaped wave form
 The spark also produces a sound, but now the frequency
corresponds to the note being played on the guitar

C6 = 1046.5 Hz
C5 = 523.25 Hz

11. Audio Oscillator Diagram – With
Coil
9V
POT1
10K
RA
RESISTOR
1K
RESISTOR
330
T
Auto Ignition Coil
POT1
10K
NMOS
7
RB
8
4
RESISTOR
NPN
ICM7555
RESISTOR
1K
2
C
0.1 or 0.01
GND
6
1
RESISTOR
10
3
100
IRF510
2N2222

12. The FaceMelter3000™
12V
C
10, 450V
..
GND
G?
RESIST OR
330
T
Auto Ignition Coil
C
10uF
PHONEJ
tip
NMOS
1
6
J?
RESIST OR
RESIST OR
+
5
2
10
IRF510
2N2222
7
4
LM386
100
-
GND
NPN
8
3

13. Data and Calculations
RA,k ohms RB, k ohms
1
11.52
11.19
2
8.41
11.19
3
4.12
11.19
4
1.003
11.19
5
11.52
7.62
6
7.86
7.62
7
4.88
7.62
8
1.003
7.62
9
11.52
4.39
10
8.35
4.39
11
4.4
4.39
12
1.003
4.39
13
11.52
1.003
14
7.44
1.003
15
4.19
1.003
16
1.003
1.003
1
11.51
11.18
2
8.87
11.18
3
4.48
11.18
4
1.003
11.18
5
11.52
7.58
6
7.88
7.58
7
5.08
7.58
8
1.004
7.58
9
11.51
3.79
10
7.87
3.79
11
4.55
3.79
12
1.003
3.79
13
11.51
1.004
14
8.08
1.004
15
4.25
1.004
16
1.003
1.004
17
11.49
10.53
18
6.42
6.14
19
3.28
2.16
20
2.557
2.047
21
1.113
1.014
22
9.08
9.68
23
7.87
7.86
24
1.465
3.96
25
1.807
2.87
C, nF
116.7
116.7
116.7
116.7
116.7
116.7
116.7
116.7
116.7
116.7
116.7
116.7
116.7
116.7
116.7
116.7
13.16
13.16
13.16
13.16
13.16
13.16
13.16
13.16
13.16
13.16
13.16
13.16
13.16
13.16
13.16
13.16
116.7
116.7
116.7
116.7
116.7
950.4
950.4
950.4
950.4
T1, div
3.3
2.9
2.2
4.3
7
5.5
4.5
3
5.8
4.5
6.2
3.9
9
6
7.2
2.9
4.4
3.9
3
2.2
3.7
3
6
4
7.2
5.6
4
2.2
6
8.8
5
4
3.7
5.2
4.3
3.9
3.4
3.1
2.7
4.3
3.8
Scale,
T2, div
seconds/div
5.1
0.0005
4.7
0.0005
4
0.0005
9
0.0002
10
0.0002
8.6
0.0002
7.6
0.0002
6.1
0.0002
7.5
0.0002
6.2
0.0002
9.8
0.0001
7.3
0.0001
9.8
0.0001
6.9
0.0001
8.9
0.00005
4.4
0.00005
6.9
0.00005
6.1
0.00005
5.3
0.00005
4.7
0.00005
5.2
0.00005
4.7
0.00005
10
0.00002
8.1
0.00002
9.2
0.00002
7.5
0.00002
6
0.00002
4.3
0.00002
6.7
0.00002
9.8
0.00001
6.1
0.00001
6.1
0.000005
5.9
0.0005
8.3
0.0002
6.7
0.0001
5.9
0.0001
5.5
0.00005
5.2
0.005
4.3
0.005
8.2
0.001
6.7
0.001
Calculated
Calculated Duty
Frequency, Hz
Cycle, %
348.8
66.99%
384.1
63.66%
446.2
57.77%
505.7
52.14%
441.9
71.52%
511.9
67.01%
587.7
62.13%
728.0
53.09%
582.5
78.37%
690.3
74.37%
897.2
66.69%
1208.7
55.13%
874.3
92.58%
1251.9
89.38%
1908.5
83.81%
3929.9
66.67%
3096.1
66.99%
3357.8
64.20%
3907.0
58.35%
4488.4
52.15%
3930.4
71.59%
4551.4
67.10%
5181.0
62.55%
6487.5
53.11%
5493.1
80.15%
6787.3
75.47%
8644.9
68.76%
12217.5
55.84%
7757.3
92.57%
10394.8
90.05%
16756.7
83.96%
34826.7
66.66%
363.3
67.65%
632.4
67.17%
1555.9
71.58%
1778.0
69.22%
3764.8
67.72%
51.1
65.96%
61.6
66.68%
154.7
57.81%
192.4
61.97%
Measured
Measured Duty
Frequency, Hz
Cycle, %
392.2
64.71%
425.5
61.70%
500.0
55.00%
555.6
47.78%
500.0
70.00%
581.4
63.95%
657.9
59.21%
819.7
49.18%
666.7
77.33%
806.5
72.58%
1020.4
63.27%
1369.9
53.42%
1020.4
91.84%
1449.3
86.96%
2247.2
80.90%
4545.5
65.91%
2898.6
63.77%
3278.7
63.93%
3773.6
56.60%
4255.3
46.81%
3846.2
71.15%
4255.3
63.83%
5000.0
60.00%
6172.8
49.38%
5434.8
78.26%
6666.7
74.67%
8333.3
66.67%
11627.9
51.16%
7462.7
89.55%
10204.1
89.80%
16393.4
81.97%
32786.9
65.57%
339.0
62.71%
602.4
62.65%
1492.5
64.18%
1694.9
66.10%
3636.4
61.82%
38.5
59.62%
46.5
62.79%
122.0
52.44%
149.3
56.72%
Note
F4
D#5
G6
A6
A#7
D#1
F#1
B2
D#3

14. 40000.0
Comparison of Measured and Calculated Frequency
35000.0
Measured Frequency, Hz
30000.0
25000.0
20000.0
15000.0
10000.0
5000.0
0.0
0.0
5000.0
10000.0
15000.0
20000.0
25000.0
Calculated Frequency, Hz
30000.0
35000.0
40000.0

15. 4000.0
Comparison of Measured and Calculated Frequency
A#7
3500.0
Measured Frequency, Hz
3000.0
2500.0
2000.0
A6
1500.0
G6
Scale notes'
frequencies measured
using an electric tuner.
1000.0
D#5
500.0
D#3
D#1
0.0
0.0
B2
F#1
F4
500.0
1000.0
1500.0
2000.0
2500.0
Calculated Frequency, Hz
3000.0
3500.0
4000.0

16. Comparison of Measured and Calculated Duty Cycles
90.00%
Measured Duty Cycle, %
80.00%
70.00%
60.00%
50.00%
40.00%
50.00%
55.00%
60.00%
65.00%
70.00%
75.00%
Calculated Duty Cycle, %
80.00%
85.00%
90.00%
95.00%

17. Conclusions
Measured values of frequency and duty
cycle were only two significant
figures, resulting in less accuracy
 The electronic tuner was more accurate
than the oscilloscope because the
tuner, like an ear, can hear smaller
differences in frequency – verified by
comparing the pitch to a piano
 The plasma guitar amplifier produced a
satisfactory sound, but the volume and
sustain could be dramatically improved
