Epiphone Valve Jr Mod Kit Instructions

Thanks for purchasing the Epiphone Valve Jr. Supreme Modification Kit. After these simple

Optional Tools/Supplies:

• Hot Glue Gun and Hot Glue.
• 9/16” nut driver or socket wrench.
• 1/2” nut driver or socket wrench.
• Fine point Sharpie Masking Tape
• Exacto Knife

Skills required:

• Basic soldering skills .
• Basic knowledge of electronics.
• The Ability to follow instructions.

Resistor Guide

• BLACK 0 K
• BROWN 1 N
• RED 2 R
• ORANGE 3 O
• YELLOW 4 Y
• GREEN 5 G
• BLUE 6 B
• VIOLET 7 V
• GREY 8 E
• WHITE 9 W

Before starting I would like you to be a little bit familiar with the circuit and with how the changes you are about to make affect the sound and performance of your amp. There are three different versions of the Valve Jr. All of them have the same basic schematic with different part values. The newer Valve Jr’s address some of the problems the older ones had but even the latest version if the Valve Jr will benefit greatly from these mods.

Changed Components:

J1: Input Jack—Some Valve Jr’s have a metal input jack that is grounded directly to the chassis. Use the provided isolation washers to break any potential ground loop and 60Hz hum that this may cause. If your amp has a plastic and metal jack it is already isolated and does not need the washers.

R2: Grid Resistor—Stock value of 68K is too high and restricts signal, replace with the 10K resistor to keep the signal strong and prevent radio frequency interference.

R1: Pull Down Resistor– Older Valve Jr’s have a stock 68K, increase R1 to 1M for increase in overall gain and improve the signal to noise ratio.

R8 and R9 : Cathode Resistor– Stock value of 2K2 runs the pre-amp tube a little on the cool side, lowering to 1k increases the current and bias for a warmer, smoother pre-amp stage.

C1 & C2: Coupling Caps— Replaces the stock caps with the same value—High Quality Orange Drop caps for better tone.

C4 : Cathode Cap—The stock 22uf cap lets full range through the first pre-amp stage, replace with 2.2uf cap to roll off just a bit of the bass for a tighter response.

C5 : Cathode Cap—The stock 22uf cap is a little low for the power tube. Replace with 100uf cap to stabilize and stiffen the power tubes response.

R14: Cathode Resistor—The stock 220 Ohm resistor runs the power tube too hot, reducing the tubes lifespan and causing a brittle tone. Replace with 270 Ohm resistor to cool the tube, increasing its life and improving tone.

C6: Filter Cap—The first filter stage of 22uf is pretty weak. Replace with 100uf cap to reduce hum and have more reserve power for increased bass response and punch.

Brightness Mod: - a 100pf cap is placed across the volume pot, brightens up the amp at low volumes and loses its effect as you turn up the gain.