If you’ve got an old Marshall, Marshall reissue, or other push-pull power, non-master volume amp, you already know it has to be cranked up fairly high to get overdriven tone. Unfortunately that also means very loud. With the PPIV (Post Phase Inverter) Master Volume kit, you can install a master volume that will allow you to achieve those overdriven tones at a much lower volume. This MV is based on Ken Fisher’s Type II, with the LarMar refinement (2.2M Ohm safety resistors). It is also the most transparent when rotated fully clockwise (maxed, or “dimed”). Please note: Beginning in 2018, instructions are now online for your convenience, allows us keep our prices competitive, and allows us to help contribute to a greener planet. Please refer to the Order Status email for links to instructions. Order Status can also be obtained online in your Account History (after registering).
(1) Alpha 250K audio dual pot
(2) 2.2M 1/2 watt resistor
(2) feet two conductor coax cable (2 conductors, 1 shield)
(1.5) feet 22GA 1000V PVC Topcoat wire (for bias supply, color may vary)
(1) Choice of Plexi, pointer, or no knob (indicate in dropdown field)
(4) inches 1/8″ shrink tubing
(6) 4″ cable ties
Installation video example (using a JCM800 Master Model 50W Mk II Lead amplifier)
Beginning in 2018, instructions for modification kits are now online for your convenience. This allows us keep our prices competitive, and helps all of us reduce paper waste. Links to PDF files will be included in the order status email when the order ships, and always available in your order history. Please add grangeramp.com to your email whitelist to ensure you receive our emails.
DISCLAIMER: User assumes all risks. Performing these modifications will most likely void the warranty on your amplifier. Working on amps can be deadly if you do not take proper precautions. Read and follow the diagram or instructions very carefully. Basic soldering skills and basic user-supplied tools are required. If you are at all unsure of your ability to perform these modifications STOP and take your amp to a professional to be modified. You can also send your amp to us for modification. Contact us for pricing.
DIFFICULTY LEVEL: INTERMEDIATE [Follow safety guidelines for working with electricity. Basic soldering skills and knowledge of working with AC/DC circuits. Identify all terminals of electronic components using data sheets. Read resistor color codes and capacitor values. Measure and connect high and low voltage AC and DC. Understand basic working of vacuum tubes. Use all functions of a multimeter. Understand Ohms law and apply to basic circuits. Work with basic hand and power tools.]