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A resistor’s value—the amount of resistance it creates—is
rated in ohms (Ω ). Larger ohm values mean more resistance.
For example, a 100Ω resistor creates ten times as much re-
sistance as a 10Ω resistor.
The resistors used in amplifiers are too small to have value
numbers printed on them. Instead, a system of colored
bands tells their values. The key to reading these bands is
provided below. However, an easier way to decode these
bands is to download one of the many smartphone apps
for this purpose.
One band will be the nearest to an end of the resistor. That
band tells the first value. Combine it with the value of band
2 to get a two-digit number (68 in our example below).
Multiply that number by band 3 (68 x 1,000 = 68,000). Thou-
sands are represented by the letter K, so this resistor is 68K
(kilo-ohms, or KΩ).
If there is a fourth band, it will be either silver or gold. This
indicates the tolerance allowed during manufacturing. The
resistors used in this kit have a +/- 5% tolerance, represented
by a gold band 4.
A magnifying glass helps a lot. The bands on a 470Ω resistor
are yellow/violet/brown, and the bands on a 47K resistor are
yellow/violet/orange. They’re easily confused!
Can’t read the colors?
You can always use a multimeter to test a resistor’s value.
Set your meter to ohms and connect the test leads on each
side of the resistor.
Capacitor values are typically printed on the component.
The key values with caps are their capacitance and voltage.
Think of a capacitor as a container that can hold electricity.
Capacitance, measured in farads, refers to how much elec-
tricity this container can hold—its capacity. One farad (1F)
would be much too large for use in an amplifier. Caps for
amps are rated in millionths of a farad, called microfarads
(μF), or trillionths of a farad: picofarads (pF). The voltage
spec for a cap refers to how much DC voltage it can handle
at any given time.
A unique property of capacitors is that they don’t allow DC
current to flow past them, only AC current. This is important
in parts of an amplifier circuit, such as the path between a
preamp stage and a power amp stage. Here, a “coupling
capacitor” will block DC voltage, allowing only the AC guitar
signal to pass.
Filter caps
Capacitors also filter out 60Hz hum, or “ripple,” after the AC
current from the wall is converted to DC. These capacitors
are called filter caps, because they filter out the ripple from
a power supply. The filter caps in this amp are the 8μF and
16μF electrolytic capacitors.
Electrolytic caps
Electrolytic capacitors contain electrolyte: a liquid or gel
that gives them a large storage capacity. Electrolytic caps
are typically polarized.
Polarized caps
Some capacitors have polarity and some don’t. It’s extremely
important to install polarized caps correctly in a circuit. The
positive lead of an electrolytic cap will be indicated by an
indented ring around one edge of the capacitor. The nega-
tive lead will often be indicated by a band of arrows pointing
to the negative lead.
Installing capacitors with the polarity backwards will make
the circuit malfunction and quickly destroy the capacitor—
even causing it to explode.
Band 1 Band 2 Band 3 Band 4
1st Digit 2nd Digit Multiplier Tolerance
6 8 x1,000 +/- 5%
68K +/- 5%
K=1,000
Blue
Read this band first (closest to an end)
Gray Orange Gold
BLACK 0 0 1 None +/- 20%
BROWN 1 1 10
RED 2 2 100
ORANGE 3 3 1,000
YELLOW 4 4 10,000
GREEN 5 5 100,000
BLUE 6 6 1,000,000
VIOLET 7 7
GRAY 8 8 0.01 +/- 10% SILVER
WHITE 9 9 0.1 +/- 5% GOLD
NegativePositive
+
25μF
8μf
How to read resistor values Capacitor values
