Step 01.01: Punching Octal Tube Socket Holes
Use a 1-3/16" chassis punch for EL34 octal sockets and a 3/4" punch for 12AX7 preamp noval sockets. Lightly grease punch threads before tightening.
M1
Chassis Layout & Mechanical Punching
Audio & InstrumentsAdvancedMulti-Week build
Hand-Wired 50W Plexi Tube Guitar Amplifier
Scratch-built 50W British tube amp head with eyelet board, custom aluminum chassis, and dovetailed birch headshell.
strumico
· updated about 1 month agoBuild progress · 0/4 steps0%
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Step 02.01: Twisting Preamp Filament Wires
Tightly twist 18 AWG green heater wires using a drill chuck, keeping twist pitch to roughly 3 twists per inch. Route wires tightly along the inside chassis corner.
Step 03.01: Gradual Variac Power-Up & Current Limiting
Insert power cable into a variable transformer with an inline light bulb current limiter. Slowly increase mains voltage from 0V to 120V over 15 minutes while measuring DC B+ supply rails.
Step 04.01: Corner Relief Cuts & Tolex Application
Roll water-based contact adhesive evenly onto the birch exterior and vinyl backing. Slice 45-degree relief cuts on corners, tucking edges firmly under gold piping.
Hand-Wired 50W Plexi Tube Guitar Amplifier
Bill of Materials & Tools
Materials
| Have | Item Name | Qty | Unit | Vendor |
|---|---|---|---|---|
| 50W Drop-in Plexi Power & Output Transformer Set | 1 | set | Sweetwater | |
| Mullard Matched Pair EL34 Power Vacuum Tubes | 1 | pair | Amazon | |
| Pre-drilled 50W Blank Aluminum Chassis | 1 | pcs | Amazon | |
| 50uF/50uF 500V Dual Can Filter Capacitors | 3 | pcs | Amazon |
Tools
| Have | Item Name | Qty | Unit | Vendor |
|---|---|---|---|---|
| Chassis Hole Punch Set (3/4" and 1-3/16") | 1 | set | Home Depot |
Milestones & Build Steps
Milestone 01 · Chassis Layout & Mechanical Punching
Mark, punch, and deburr transformer cutouts, tube sockets, and potentiometers.
Step 01.01·Punching Octal Tube Socket Holes
Use a 1-3/16" chassis punch for EL34 octal sockets and a 3/4" punch for 12AX7 preamp noval sockets. Lightly grease punch threads before tightening.
1Callouts & Parts
- ①dd
Milestone 02 · Eyelet Board Assembly & Lead Dressing
Stake brass eyelets onto Garolite board and populate passive components.
Step 02.01·Twisting Preamp Filament Wires
Tightly twist 18 AWG green heater wires using a drill chuck, keeping twist pitch to roughly 3 twists per inch. Route wires tightly along the inside chassis corner.
Milestone 03 · Power Supply & High-Voltage Testing
Wire mains transformer, bridge rectifier, multi-can caps, and test bias with a variac.
Step 03.01·Gradual Variac Power-Up & Current Limiting
Insert power cable into a variable transformer with an inline light bulb current limiter. Slowly increase mains voltage from 0V to 120V over 15 minutes while measuring DC B+ supply rails.
Milestone 04 · Dovetailed Headshell Cabinet & Tolex
Cut Baltic birch finger joints, roundover cabinet corners, and apply levant vinyl tolex.
Step 04.01·Corner Relief Cuts & Tolex Application
Roll water-based contact adhesive evenly onto the birch exterior and vinyl backing. Slice 45-degree relief cuts on corners, tucking edges firmly under gold piping.
