Need to replace the reverb box for your guitar amplifier, but don't know where to start? Let Chris Fantana, the head of Rift, be your guide.

Hi Anton, thank you very much for your questions in the last printed edition of my column. But don't worry, I will continue to answer readers' questions online on Guitar.com, so please continue to send them.

Just like speakers, reverberation boxes have many different circuit design features, so you need to order similar products to ensure correct operation. Well, almost. Let's break it down...

This is a typical Fender reverb tank code: 4AB3C1B. Sadly, I am very familiar with this, it is by far the most commonly used tank in guitar amplifiers. The seven-digit code is important because it tells us everything about it, from the size to the length of the reverb, to the direction of the connector. It even tells us which way to install it in the cabinet.

There are three different tanks to choose from. Type 4 is 16.5 inches long and has four rewind springs arranged in 2×2. Type 8 is 9.5 inches long and has three springs. Type 9 is 16.5 inches long and has 6 counter springs arranged in 3×2. This usually applies to keyboard and pedal steel. You may find Type 1 tanks, but these have been discontinued and replaced by Type 8.

Type 4 tank has four springs in a 2×2 setting

This matches the output impedance of the reverberation transformer or drive valve/transistor.

A – 8 ohm B – 150 ohm C – 200 ohm D – 250 ohm E – 600 ohm F – 1,475 ohm

This matches the input impedance of the recovery stage.

A – 500 ohm B – 2,250 ohm C – 10,000 ohm

This is the length of the reverberation. 1 is very short, in 1.2-2 seconds. 2 is medium, at 1.75-3 seconds. 3 is very long, at 2.75-4 seconds.

A: Input ground/output ground. B: Input grounding/output isolation. C: Input isolation/output grounding. D: Input insulation/output insulation. E: No external channel.

Some tanks, such as those found in Fender's 6G15 independent reverberation unit, have a transport lock to prevent the spring from bouncing during transport. 1 means there is no lock, 2 means there is a lock.

A: Horizontal opening facing upwards B: Horizontal opening facing downwards C: Vertical joints upwards D: Vertical joints downwards E: One end input upwards F: One end output upwards

The shorter Type 8 tank has three springs

How does this all work in practice? Let's take a look at the classic Fender fuel tank 4AB3C1B. The code tells us that this is a 16.5-inch 2×2 spring box, designed to be installed on the floor of the box, with insulated input and long reverberation time. The input impedance is 8 ohms, and the output is 2,250 ohms.

If you want to replace it with a smaller 9.5-inch fuel tank, then you can order 8AB3C1B. Want the same size tank but shorter reverberation time? Then select 4AB2C1B. If the input/output, mounting plane, and connector configuration specifications remain the same, you can switch between different tank types and reverberation times without any problems.

Marshall usually uses a very different fuel tank in their amplifiers. The 4FB2A1C is a 16.5-inch cabinet with 1,475 ohm/2,250 ohm impedance, medium reverberation length, and insulated input. It is designed to be installed on the side of the cabinet with the connector facing up (although it is usually found facing down).

The Type 9 tank is an interesting tank. If you are a big fan of spring reverb, then I strongly recommend that you try one of them in an amplifier. The space and depth are great, but you may encounter some extra splashes in some circuits.

Replacing a reverb tank is cheap—usually around £30 in the UK—and is a great way to adjust the sound of an amplifier at a very small cost. Good luck and enjoy!

Visit riftamps.com to view Rift's series of boutique amplifiers made in the UK.

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