Mod 101 User manual

1Copyright © 2015 by modkitsdiy.com
Use these instructions to learn:
How to build a tube amp.
How to bias a tube amp for 6L6GC or EL34 power tubes.
Some modifications for altering the tone of a tube amp.
This tube guitar amplifier circuit is basic and classic. It can produce warm clean tone at low volume and
rich overdrive distortion at higher volume.
1 5/
16"
ON
OFF
POWER STANDBY BASS TREBLE VOLUME INPUT
0 10
5
2 8
3
4 6
7
1 9
0 10
5
2 8
3
4 6
7
1 9
0 10
5
2 8
3
4 6
7
1 9
MOD 101
TUBE AMP KIT
MOD 101 GUITAR AMP KIT (K-MOD101)
www.modkitsdiy.com

2
TABLE OF CONTENTS
TOOL LIST …………………………………………………………………………...3
PARTS LIST …………………………………………………………………………...4
SAFETY …………………………………………………………………………...6
SOLDERING TIPS …………………………………………………………………...7
WIRING TIPS ……………………………………………...................................8
HARDWARE FASTENING TIP …………………………………………………...9
STEP BY STEP ASSEMBLY INSTRUCTIONS …………………………………...9
Section 1 – Mounting of Top Components …………………………………...9
Section 2 – Mounting of Front Components ………………………………….12
Section 3 – Mounting of Rear Components ………………………………….13
Section 4 – Mounting Internal Terminal Strips and Passive Components ….14
Section 5 – Solder the Filter Components ………………………………….16
Section 6 – Connect the Front Mounted Components ………………….18
Section 7 – Connect TR2 to the Impedance Selector Switch ………………….20
Section 8 – Connect the Tube Sockets ………………………………….22
Section 9 – Connect the Terminal Strip Interconnects ………………….23
Section 10 – Connect the Tube Filaments ………………………………….23
Section 11 – Insert the Strain Relief and Connect the Power Cord ………….24
Section 12 – Fasten the Rubber Feet to the Chassis Cover ………………….25
Section 13 – Fasten the Chassis Cover to the Chassis Box ………………….25
Section 14 – Set the Bias of the Power Tubes ………………………….26
Section 15 – Fasten the Steel Cage to the Chassis Box ………………….28
Section 16 – Modifications ………………………………………………….29
PARTS LIST DRAWINGS (4)
There are four parts list drawings separated from these instructions to help you find
each part and identify it.
ASSEMBLY DRAWINGS (25)
There are 25 assembly drawings separated from these instructions to help you with each
step of the assembly.

MOD 101 GUITAR AMP KIT – BACKGROUND
The MOD 101 Guitar Amp Kit was designed for anyone who is interested in building their own tube guitar
amplifier head and learning some simple circuit modifications that can be used to tailor the sound to better suit
their tonal preference. The modifications are instructions and supplied parts that allow you to build 32
variations of the amp circuit.
The amp is meant for concert stage volume (up to 60 Watts). It is equipped with an impedance selector
switch, giving you the flexibility to use it with the speaker cabinet of your choice. (We recommend using it
with a speaker cabinet that has an overall wattage of at least 100W). Use 16 AWG speaker cable to connect
from the amplifier to your speaker cabinet. Set the amplifier switch to match the overall impedance of the
speaker cabinet.
3
TOOL LIST
Wire Strippers
Needle Nose Pliers
Cutting Pliers
Desoldering Pump
Solder (60/40 rosin core)
Soldering Station
Phillips Head Screwdrivers
Slotted tip screwdrivers (3mm tip)
Digital Multimeter (DMM)
Alligator Clip Test Leads (to fit DMM)
Channellock Pliers (or similar type)
Miniature Round File (fine cut)

PARTS LIST
Please see the parts list drawings for help with finding and identifying each part
along with corresponding part numbers.
RESISTORS:
Description Quantity
1Ω 1/2W 2
1Ω 5W 1
47Ω 1/2W 1
360Ω 10W 1
470Ω 1/2W 3
820Ω 1/2W 2
1kΩ 1W 1
1kΩ 5W 2
1.5kΩ 1/2W 2
2.4kΩ 1/2W 1
2.7kΩ 1/2W 1
4.7kΩ 1W 1
5kΩ 5W 1
6.8kΩ 1/2W 2
20kΩ 1/2W 1
22kΩ 1/2W 1
68kΩ 1/2W 2
82kΩ 1W 1
100kΩ 1/2W 1
100kΩ 1W 3
220kΩ 1/2W 2
220kΩ 1W 2
1MΩ 1/2W 4
TERMINAL STRIPS:
Description Quantity
3 lug terminal strip (vertical) 5
3 lug terminal strip (2nd lug common) 1
4 lug terminal strip 2
5 lug terminal strip 1
6 lug terminal strip (no common) 2
6 lug terminal strip (2nd lug common) 3
8 lug terminal strip 1
HARDWARE:
Description Quantity
#10 screws 8
#10 lock washers 6
#10 hex nuts 8
#8 screw 4
#8 self-tap screws 8
#8 hex nuts 4
#6 screws 22
#6 lock washers 20
#6 locking lugs 4
#6 hex nuts 22
#4 screws 4
#4 lock washers 4
#4 hex nut 4
TUBES:
Description Quantity
12AX7/ECC83 1
12AT7/ECC81 1
6L6GC 2
EL34 2
TRANSFORMERS:
Description Quantity
Power Transformer 374BX 1
Output Transformer 1650P 1
4
CAPACITORS:
Description Quantity
250pF 500V 1
500pF 500V 1
.001µF 630V 1
.022µF 630V 2
.047µF 630V 1
.1µF 630V 4
22µF 50V 2
22µF 500V 4
80µF 450V 2
220µF 50V 1

MISCELLANEOUS PARTS:
Description Quantity
Solid state diode 1N4007 3
250kΩ audio pot 2
1MΩ audio pot 1
25kΩ linear pot 1
Chicken head knob 4
Impedance switch & output jack 1
9 pin miniature tube socket 2
Octal tube socket 2
Tube clip 2
Rubber Grommet 5
Strain Relief 1
Input jack 1
Purple jewel 1
Power switch (DPDT) 1
Standby switch (SPST) 1
2A fuse 1
Fuse holder 1
Light bulb 1
Lamp holder 1
Handle with mounting hardware 2
Rubber feet 4
Power cord 1
Steel chassis box and cover 1/each
Steel cage 1
Labels 1 set
Green 20 AWG wire 10 feet
Red 22 AWG wire 20 feet
5

6
DANGER
HIGH VOLTAGE
MAY BE PRESENT
ON FILTER CAPACITORS
DO NOT TOUCH!
SAFETY
Tube amps operate at high voltages that have the potential to injure and kill. Please remember the following
when working on this project.
Only work on the amp when you are wide awake and sober.
Do not plug the amp in until you have gone through all of the instructions, checking and re-checking
each step.
Do not turn the amp on until you have connected it to a speaker cabinet.
Be aware that tubes become very hot when the amp is on and can take up to 10 minutes to cool down
after power is turned off.
Work in a ventilated area when soldering.
Always follow the one hand rule when working with an amp that is connected to power or may have
voltage present. (Any amp that has been plugged in at one time, may have high voltage present).
ON STANDBY
The one hand rule (pictured below): is a safety precaution for working on an amp that is
plugged in or could potentially have high voltages present. Using alligator clips with your
DMM, clip the ground side to the chassis and use the other side to probe at various test points
with one hand. This prevents a fatal shock which can result from current passing through the
heart. (Many people even put their other hand in their pocket or behind their back).
Always probe the amp for dangerous voltages at several test points before working on it, even if it has been turned
off and unplugged for months.
Test points include:
Both Standby Switch Terminals
Each positive end of polarized filter caps
If you smell or see smoke, hear something pop, or the chassis becomes too hot to touch, turn off
power and unplug immediately.

SOLDERING TIPS
1. Bend the component lead
and wrap it around the
connection point.
2. Wrap the component lead
so that it can hold itself to the
connection point.
3. Heat up both component
lead and connection point with
the soldering iron.
4. Apply solder to both
component lead and
connection point.
2. Apply fresh solder to mix in
with old solder joint
1. Heat up old solder joint
with the soldering iron.
3. Use a de-soldering tool to
remove the old solder joint
while it is heated.
De-Soldering Tip
7
It is important to make a good solder joint at each connection point. A cold solder joint is a connection that
may look connected but is actually disconnected or intermittently connected. (A cold solder joint can keep
your project from working.)
Follow these tips to make a good solder joint. Take your time with each connection and make sure that all
components are connected and will remain connected if your project is bumped or shaken.
Bend the component lead or wire ending and wrap it around the connection point.
Make sure it is not too close to a neighboring component which could cause an
unintended connection.
2. Wrap the component lead so that it can hold itself to the connection point.
Touch the soldering iron to both the component lead and the connection point allowing both to
warm up just before applying the solder to them.
Be sure to adequately cover both component lead and connection point with melted solder.
Remove the soldering iron from your work and allow the solder joint to cool. (The
solder joint should be shiny and smooth after solidifying.)
Cut off any excess wire or component leads with cutting pliers.
Clean the soldering iron's tip by wiping it across the wet sponge again after making the
solder joint.

WIRING TIPS
There are two different gauges of stranded wire included with the kit. Use 22 AWG wire unless noted
otherwise in the instructions. The lower AWG (American Wire Gauge) number signifies a thicker gauge of
wire, which can handle more current. (It is important to use the thicker gauge wire where specified in the
instructions.)
8
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
20AWG
22AWG
Because of the electro-magnetic
properties of current traveling through a
wire, there are wiring conventions used
when making wire connections.
A) Twist the wires together where
indicated in the instructions.
B) If two wire paths intersect, try to
have them cross over each other as
perpendicular as possible. (You should
follow the path of the wires shown in
the instructions).
A) Twisted Wires
B) Perpendicular
Intersection
Measure the wire by running it along its actual path (shown in the drawings) and then cutting it with
your wire cutters at a length that will give it a little bit of slack after stripping off the insulation and
soldering.
It is important not to make the wires too long.
Be careful not to strip away strands of wire when you remove the insulation at the end of wires.
Be careful not to burn the insulation of nearby wires with the soldering iron.
With the terminal strips used in this kit, you might want to connect the wires to the lower holes
and components to the upper holes. (Doing this can make it easier to change components for
modification).
5W 1K
5W 1K
Wires connected to lower terminal holes.
Components connected to upper terminal
holes.

STEP BY STEP ASSEMBLY
Please refer to the respective drawings for each section. We recommend browsing over the instructions and
looking at all drawings once before actually beginning to assemble the kit.
HARDWARE FASTENING TIP
When fastening components with mounting hardware (screws, lock washers, and hex nuts), the lock washer and
hex nuts should be fastened on the other side of the chassis from the head of the screw in the order pictured
below.
SECTION 1 – Mounting of Top Components
Please refer to Drawings 1 – 6. Find your chassis box. Drawing 1 identifies the names of
components that you will be mounting to the top of the
chassis box.
COLD HOT
Step 2
Drawing 2 shows where to stick the bias label. Make sure to line up the hole in the
sticker with the hole in the chassis box.
Step 3 – Mount the bias pot
Drawing 3 shows where to mount the bias pot. Bend down the tab on the top of
the pot for a better fit against the chassis top. Make sure the solder lugs of the pot
are directed toward the front of the chassis. (Turn the shaft all the way to cold).
25KL
Chassis Front Bent back mounting tab
Step 4 – Mount the rubber grommets
Drawing 3 shows where to mount the five rubber grommets. Squeeze the grommet
into the hole and push it into place with your fingers.
9
Chassis
Screw Head
Lock Washer Hex Nut
Component Mounting
Bracket
(5)
Step 1
Use a fine cut miniature round file to very lightly file away
the paint coating only from the inside edge of each chassis
hole.
(The chassis provides the ground connection for many
components so it is important that the inner edge of
these holes are not insulated by the paint coating).

10
(2) (4)
(4)
(4)
Step 5 – Mount the 9 pin miniature tube sockets
Drawing 3 shows where to mount the two 9 pin miniature
sockets. Make sure that pins 1 & 9 face away from the rear edge
of the chassis. (Use #4 hardware).
Step 6 – Mount the octal tube sockets and tube clips
Drawing 3 shows where to mount the two octal sockets along with their tube clips. Make sure that pins 1 & 8
face away from the rear edge of the chassis. (Use #6 hardware)
(2)
(4)(2)
(4)
(2)(2)
Use locking lugs in place of lock washers for the
mounting screws which face away from the rear
chassis edge.
The mounting holes of the tube clip are placed
over those of the octal socket. The screws are
then placed through both sets of mounting holes.
Step 7 – Mount both side handles
Mount both handles to the sides of the chassis box using their supplied #8 hardware. (Doing this step will
help you flip the chassis when mounting the two heavy transformers).
TOP
.25
"
Mount both side handles.
(4)
(4)
(2)
1
2
3
4
5
6
7
8
Chassis Rear