In addition to the reference images on this page, you
will need to refer to the BOM
and layout PDFs during your amplifier's construction:
∙ Printable
Silkscreen Layer
∙ Printable Top Layout
View
Three positive polarity markings (+) can be found on the
circuit board: C1, LED, and V+. The longest lead of an electrolytic capacitor or
diode corresponds to positive polarity.
I have also printed several switch symbols, _/ _, on the
PCB, explained as follows:
∙ The two switch symbols parted by the words "Bass Boost"
(below the DIP socket) will be connected to a DPDT switch to enable or disable
bass boost. Only short these terminals if you desire to permanently disable bass
boost!
∙ The two switch symbols enclosed by the Alps RK097 Potentiometer rectangle
should each be closed/shorted if you wish to omit the volume control. If the
RK097 is omitted, you must also either short its switch terminals, or attach a
power switch. These unmarked terminals are directly beneath capacitors
C2_L/C2_R, and are parallel with the "RK097" label.
∙ The last switch symbol, found near the DC jack (MJ-2509N), must be
shorted if the DC jack is omitted.
Note: You should solder after each
step, then cut off extra leads with diagonal cutters. Please read the
pre-assembly section if you plan to omit or bypass any features.
1. Begin by mounting the 8-pin DIP socket. Be sure to match to
socket's orientation notch to the label on the circuit board. Bend two adjacent
corner pins on the bottom side of the circuit board (such as pins 1 and 8), with a flathead screwdriver to hold the
socket in place while soldering.
2. Mount both sets of resistors R2, R3, R4, and RB. The
labels will now be hidden beneath the DIP socket, so refer to the above pictures
and diagrams. Resistors R2 are closest to the top of the PCB and subsequent
resistors follow in the stated order. If you would like to permanently bypass
the bass boost feature, short each set of RB terminals.
3. Next, mount capacitors C2_R, C2_L, CB_R, and CB_L. These polypropylene
capacitors are non-polar, i.e., they can be inserted in either direction. As
before, you may find it useful to bend the capacitors' pins with a screwdriver
to hold them in place before soldering.
4.
Connect four short wires to the toggle switch as indicated in the diagram at
right. It may be useful to use one color of wire for the right channel
(terminals A and B) and another color of wire for the left channel (terminals C
and D).
Try to minimize wire length.
Unnecessarily long wires will add inductance and capacitance to the feedback loop,
potentially causing unwanted
noise or oscillation.
5. Insert the Texas Instruments TLE2426CLP chip into its
respective destination. The center pin pin will bend easily and allow you to
push the chip into place. It is crucial that this chip is properly oriented!
6. Seat the input audio jack (STX-3100-3C), the volume
potentiometer (RK097), and the output jack (STX-3100-9N). For proper alignment,
you may need to hold these jacks in place while soldering their one pin.
7. Mount capacitor C1, observing correct polarity. If
you use a taller capacitor than the default recommendation, you should rotate it
90 degrees to the right (so that it lays flat against the PCB)--otherwise, the
tin's lid will be obstructed.
8. Mount resistor R_LED.
9. Seat the DC jack, MJ-2509N. It is usually necessary
to hold this jack in place while soldering.
10. Insert the LED, noting polarity. Bend the LED
forward 90 degrees so that it is aligned with the DC jack; it will again be
helpful to bend the LED's pins before soldering.
11. Last, insert the red lead of the 9V battery
connector to terminal V+ and the black lead to terminal V-.
12. Insert the National Semiconductor operational
amplifier (or other opamp) into the DIP socket, once again observing socket orientation.
Now is a good time to test your new cMoyBB. Connect a
new 9V battery and a cheap pair of headphones to the amp. Barely turn the volume
knob on and check for obvious faults: Ensure you hear silence from your
headphones and that no chips or components are overheating (everything should be
cool to the touch). Engage and disengage the bass boost switch and check that no
problems arise.
Assuming this preliminary test passes, connect the amp
to a cheap source to verify its full functionality.
Once you have a working amplifier, you should clean the
PCB. Use rubbing alcohol and an old toothbrush to scrub excess flux from the
bottom of the circuit board. See
Tangent's video tutorials
for help. Failure to clean the PCB can eventually lead to corrosion of the PCB's
72 soldering joints--not good!
Packing the amp into an Altoids tin may be the most
challenging step. First, print the top layout view,
which will serve as a pattern. Use a Dry-Erase marker and the pattern to mark
approximate jack locations before punching holes with the hole punch. Since the
bass boost switch is external to the PCB, it can be mounted freely.
Tips:
∙ Although it is not necessary if you punch holes in
exactly the right spots, it’s a good idea to use some method to insulate the PCB
from shorting out to the tin. Apply hot glue to various spots on the bottom of
the PCB; avoid gluing soldering joints. Alternatively, you may use foam,
cardboard, or layers of electrical tape to insulate the bottom of the circuit
board.
∙ Cut holes slightly too large for the RK097 and input
jack; these holes will be covered anyway. This will allow you to more easily
wiggle the PCB into place.
∙ Do not use the washer or nut with the Alps RK097 potentiometer. The input, output, and DC jacks
are arranged so that the amp will already be securely
positioned without the volume pot. The RK097’s washer & nut are too large
for the tin’s lid to close easily (though it is possible). As previously mentioned,
the potentiometer’s hole and threads will be covered up once a volume knob
is mounted.
∙ To lock the LED in place in its grommet, use a
quick drop of hot glue--if you apply too much heat for more than a second or
two, you will burn out the diode! If you have a difficult time inserting the
LED grommet, trim off the thickest 2 plastic "legs." The hot glue will hold
it in place.
Bass Boost cMoy v2.01 Assembly FAQ
