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Amp Tech

Guitar amplifiers mods, maintenance and more.

Fender Tone Stack From Board to Pots Mod

Fender Tone Stack moved from board to pot to reduce hiss, hum and Parasitic Oscillation.

The following tone stack mod will help reduce or remove hiss, hum and Parasitic Oscillation in your Fender tube amp. We will be moving the tone stack of a Fender Blackface or Silverface Amp from the board to the pots. This mod reduces about 2-3 feet of grid wire. Included is a detailed layout of how it's done.

Fender Bassman Amp Tone Stack Mods

Fender Bassman Tone Stack Mods

In this file we will be modifying a Fender Bassman amp tone stack to sound more like the original 59' Bassman or Marshall Plexi on the bass channel and warm up the normal channel a bit. These mods also apply to similar Bassman circuits like the (AA371, AA165, AA864, AC568 etc... ) The Fender Bassman amp tone stack caps include 3 caps in the normal channel (250pf ceramic treble tone cap, .047uf mid tone cap and a .1 uf bass tone cap) and 3 in the bass channel (350pf ceramic treble tone cap, .1uf mid tone cap and a .1uf bass tone cap). Note other circuits may differ slightly in the cap values but the mods are the same.

Fender AB165 Driver Circuit Mod

Fender AB165 Driver Mod Layout

The Fender AB165 Bassman is a great guitar and bass amp, but for guitar it sounds a bit dark, muddy and lacks the high end chime that prior Bassman models where famous for. The driver circuit mod converts the AB165 circuit to sound very similar to older tweed Bassmans like the famous 59' model. After the mod you will have a great sounding guitar amp that takes pedals very well. Great amp for Blues, Blues Rock, Classic Rock, Country, Funk etc. The mods are simple and if you don't like them it's easy to convert back to the original circuit.

Fender Mid Range Control Pot Mod

Add a Mid-Range Pot To Your Fender Amp

This file will show you how to add a mid range pot to your fender amp. Instead of adding a mid pot Fender often used a fixed 6.8 resistor instead. The 6.8k resistor is soldered to the bass pot (2 lug) wiper to (1 lug) ground with the (3 lug) left untouched. You can also replace the 6.8k resistor with a 10k resistor for more mids without a pot or a lower value for less mids.

2x12 Guitar Speaker Cabinet Mono/Stereo Wiring

2 x12 Mono/Stereo Speaker Wiring Diagram 8 or 16 ohm speakers

Wiring a 2x12 Guitar Speaker Cabinet with 1 x Stereo and 1 x Mono Jack. We will use 8 or 16 ohm guitar speakers. 4 ohm speakers are not recommended. Using 2 x 8 ohm speakers results in 8 Ohms to each channel in stereo or 4 ohms mono. Using 2 x 16 ohm speakers results in 16 ohms to each channel in stereo or 8 ohms mono. When mounting the jacks use 2 separate mounting jack plates mounted on a non-conductive surface.

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