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Marshall JCM 900 2501 SL-X Combo Amp : Review

Marshall JCM 900 2501 SL-X Combo

Front Panel

It is furnished with a simple front panel. The two channels, A and B, share the equalization section. Let's see the controls of this Marshall Combo.

Power switch



It helps to prolong tubes life. Use this switch, and not the Power, when you make a break. The tubes filaments will remain heated and ready to start again.

Input jack

Here you can connect your instrument.

Pre Volume

Choose a lower value to obtain a clean Tone. Higher for a crunch or overdrived sound.


It is a secondary gain level.

Master A

The overall volume of the first channel.

Master B

It is active only if no footswitch is connected.

The equalization section

It is shared between the two channels. The circuit is passive, so the three controls are interactive.


It modifies the high frequencies.


The middle frequencies.


Adjusts the low frequencies


Turn it right to produce a more brilliant and clear sound.

Footswitch Jack

Connect the footswitch, P801, to this input.

Rear panel

Let's see the the JCM 900 2501 SL-X rear panel

Effects Loop level

With this selector the level can be modified from -10dBV to +4dBm. Generally, modern effects are at +4dBm.

Send & Return

These 2 jacks allow you to send your sound in an external effect and receive it processed.

Recording compensated Output

Send your sound directly to a recorder or a Mixer. It is filtered, so to be optimized for the recording.

Direct Output

The pre signal, unfiltered, can go directly in another amplifier.

Loudspeakers Outputs

Two Outputs for loudspeakers.

Impedance selector

Matches the impedance to the loudspeakers impedance.

Valve failure led

This led is red when output valve fails.

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