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Amp Tech

Guitar amplifiers mods, maintenance and more.

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.

Poor Mans Speaker Tester

Poor Mans Speaker Tester Diagram

We all will eventually be in a situation when our amp rig gives out, but how do we know if it's a blown speaker or your amp went bad. This simple test can be done without any kind of test equipment such as a meter. We will need the following: C or D Battery, 1/4" speaker cable and a spare wire.

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