Marshall JCM800 MODIFIED Quick Start Guide

WARNING! SAFETY INSTRUCTIONS

PLEASE READ THIS MANUAL CAREFULLY BEFORE PLUGGING IN. FOLLOW ALL INSTRUCTIONS AND HEED ALL WARNINGS.

Warning: Before going any further, make sure that your amplifier is compatible with your mains electricity supply. If you have any doubt, please seek help from a qualified technician – your Marshall dealer can help you with this.

MAINS INPUT & FUSE

The specific mains input voltage rating that your amp has been manufactured for is indicated on the rear panel of the amp. Your amp is provided with a detachable mains (power) lead, which should be connected to the mains input socket on the rear panel of the amp. The correct value and type of mains fuse is specified on the rear panel of the amp.

Never attempt to bypass the fuse or fit one of the incorrect value or type.

IMPORTANT SET UP INFORMATION

1. When using your amp with one or more speaker cabinets, make sure that they are connected to the correct loudspeaker jack sockets.Warning: Failure to do the above may damage your amp. When connecting a speaker cabinet make sure that you use a proper speaker cable. Never use a screened (shielded) guitar cable for this purpose.
2. Ensure that the power switch is set to the off position and the standby switch is set to standby.
3. Connect the supplied mains (power) lead into the mains input on the rear panel first and then into an electricity outlet.
4. Ensure that any master, volume and/or output level controls on the front panel are set to zero.
5. Plug your guitar into one of the input jack sockets on the front panel.
6. Turn the front panel power switch on and wait a couple of minutes.
7. Turn the volume up to your preferred level and you're ready to play.

TRANSPORTING YOUR EQUIPMENT

Please ensure that your amp is switched off, unplugged from the mains electricity supply and all removable cables have been disconnected from your equipment before attempting to move it.

Only move the amp on its own; do not attempt to move it while it is stacked on top of a cabinet or other equipment.

SPECIFICATION

The Marshall JCM800 series made history. Its appeal has lasted decades and crossed countless genres. Despite the versatility of the amplifiers, some guitarists wanted more and modified the JCM800 2203 amp to achieve their desired tone. As a result, the JCM800 MODIFIED adds some of the most popular modifications to the iconic standard model to satisfy an even wider range of requirements.

JCM800 MODIFIED

FRONT PANEL FUNCTIONS

1. POWER SWITCH: Turns the amp on and off.
2. STANDBY: The standby switch is used in conjunction with the power switch to warm up the amplifier before use. Always turn the power on for two minutes before switching the standby switch to the ON position. The standby switch should be set to the OFF position during breaks in performances instead of leaving the amp on full power.
3. PRESENCE: Adjusts the high frequencies of the power amp. Increasing the high frequencies adds more bite to your sound.
4. BASS: Adjusts the low frequencies of the pre-amp. It will add bottom end and depth to your sound.
5. MIDDLE: Adjusts the mid frequencies of the pre-amp, giving you anything from scooped mids to a fat and full sound.
6. TREBLE: Adjusts the upper frequencies of the pre-amp. Your tone will get brighter as it is turned up.
7. MASTER VOLUME: Turn clockwise to increase the amp's output volume.
8. PRE-AMP VOLUME: Increasing the pre-amp volume allows you to overdrive the amp to create distortion.
9. HIGH INPUT: This input gives higher gain response (less headroom, more distortion).
10. LOW INPUT: This input gives lower gain response (more headroom, less distortion). Note: Choose the input channel that complements your guitar. High output guitars may benefit from the extra headroom in the low input. Lower output guitars may benefit from the extra gain in the high input channel.
11. TIGHT SWITCH: When engaged, this switch cuts some of the low frequency content, giving a tighter sound to retain clarity at higher gain settings.
12. CLIP SWITCH: When in the centre position, the additional gain and clipping is switched off. When switched to the left position (I), additional gain and clipping is switched in. When switched to the right position (II), even more gain and clipping is switched in.
13. MID-SHIFT: When engaged, this switch adds fullness to the midrange of the sound.

REAR PANEL FUNCTIONS

1. EFFECTS LOOP LEVEL: Choose between the two different loop levels to match the type of effect(s) connected to the effects loop. Press the button inwards for a level that suits floor pedals ( -10 dBV ) or leave the button pressed outwards for a level that suits rack processors ( +4 dBV ).
2. EFFECTS LOOP BYPASS: Engages/disengages the effects loop. The effects loop is engaged when the switch is pushed inwards.
3. EFFECTS LOOP RETURN: Returns signal from effects loop/outboard equipment.
4. EFFECTS LOOP SEND: Sends signal to effects loop/outboard equipment.
5. & 6. SPEAKER OUTPUTS: Connect one or two speaker cabinets here using 1/4" jack speaker cables. Warning: Always ensure the output impedance selector is set to the appropriate impedance for the load of your setup (speaker cabinets). Never use this amp without a speaker or load.
6. OUTPUT IMPEDANCE SELECTOR: Matches the amplifier's output to the load impedance. Ensure the amp is completely powered down before turning the selector. The impedance selected on the amp must match the total impedance of the speaker cabinet(s) being used. Common setups include:
   • If the amp is running into a single 16Ω cabinet, the selector should be set to 16Ω.
   • If running into two 16Ω cabinets, the selector should be set to 8Ω.
   • If running into two 8Ω cabinets, the selector should be set to 4Ω.
   Warning: Failure to comply with these points may result in damage to the amplifier.
7. MAINS SELECTOR: Matches the amplifier mains transformer voltage to the incoming mains voltage. The mains selector must be set to the voltage of the mains supply. Your amp should be completely powered down before the selector is turned. Warning: Consult a qualified technician before adjusting the mains selector.
8. MAINS INPUT: The supplied mains power lead is connected here.
9. MAINS FUSE: The correct value of mains fuse is specified on the rear panel.
10. H.T. FUSE: The correct value of H.T. fuse is specified on the rear panel.