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Marshall JCM 900 Combo Specifications

Updated March 23, 2017

Marshall Amplifiers are known throughout the rock music community for their overdriven tone and the sound levels that they generate. The JCM900 amplifier family is a valve amplifier that utilises vacuum tubes in the power amplification circuit, generating a unique sound that is unlike solid-state amplifiers. The JCM900 family includes both combo and head-only configurations.

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JCM900 Models

The JCM900 line of amplifiers covers a variety of configurations. They are available as an amplifier head only, separate from the speaker cabinets. The JCM900 line also includes a number of combo amplifiers with the head built into the speaker cabinet.

Power Ratings

JCM900 combo amplifiers carry a range of output power ratings, making them suitable for a variety of performance and practice situations. The 4101 and 4102 models are rated at 100 watts RMS of output power. The lower powered 4501 and 4502 models are each rated at 50 watts RMS.


A combo amplifier is a self-contained unit, with speakers and the amplification electronics contained in a single unit. The 4101 model contains a single G12-100 12-inch speaker, while the 4102 amplifier has two 12-inch G12-175 speakers built into the unit. The 50-watt amplifiers follow a similar pattern. The 4501 combo has a single 12-inch G12-75 speaker. The 4502 amplifier houses two 12-inch G12-75 speakers. All of the speakers are manufactured by Celestion.

Cabinet Dimensions

The dimensions of the combo amplifier are determined by the number of speakers that the unit is designed to house. The single speaker models ( 4101 and 4501) are 500mm wide, 470mm high and 290mm deep. The larger twin speaker units (4102 and 4502) are 670mm wide, 520mm high and 250mm deep.

Dual Channel Amplifiers

The JCM900 amplifier has two channels that are independently controllable, and can be switched by the musician through the use of a foot-switch. This feature enables you to form two different gain, volume and reverb (if equipped) profiles from a single amplifier and switch between them without having to adjust the amplifier controls during a performance.

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About the Author

Warren Rachele has been writing since 1991. He has written two books, as well as articles on topics including programming and spirituality for "Your Church" and "PRISM" magazines. Rachele holds a Bachelor of Science in computer science from Regis University and a Master of Divinity in theology from Denver Seminary.

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