Marshall JCM 900 manual

Marshall JCM 900
6.8 · 3
PDF manual
 · 4 pages
English
manualMarshall JCM 900

HI GAIN DUAL REVERB

The Dual Reverb range was designed for versatility with two independently controlled footswitchable
channels, each voiced totally differently.
Channel A is voiced for brilliant clean tones with the gain control (item 2) on lower settings and
crunch to lower gain lead as you turn it up.
Channel B is boosted with enough gain (item 3), for fearsome lead tones, ranging from classic on
lower settings to contemporary screaming solos on maximum.
Channel master volumes (items 9 & 11) and individual channel reverb controls (items 8 & 10) give
you incredible control and all round versatility in either, head or combo form.

VALVE OUTPUT POWER

The JCM 900 range use high quality 5881 output valves (x2 in 50 Watt models, x4 in 100 Watt
models) for their unique distortion properties and fluid tone.
With most valve amplifiers, particularly Marshalls', the best sounds are achieved when the Master
Volumes are set high enough to be utilising the driving power of the output valves to the full.
This delicate working balance between the pre-amp and power amp levels can only be achieved by
experimentation.
You will find that all the JCM 900 models like to work hard and are designed to withstand prolonged
use at full power quite readily.The PB100 Power attenuator is ideal for this use (connects between
amp and cabinets) as it will allow you to run your amp at full power but keep the overall volume low.
The important thing to remember here is that it is the interaction between all the controls that plays
a part in achieving your sound.
1. Input Jack
Connects the instrument to the amplifier.
(A high quality screened lead must be used).
2. Channel ‘A’ Pre-Amp Gain Control
Sets the gain level for channel “A”. Lower
settings give clean sounds - higher settings for
medium drive and crunch rhythm.
3. Channel ‘B’ Lead Gain Control
Sets the gain level for boosted Channel B.
Lower settings give slight overdrive - higher
settings for maximum drive and sustain.
4,5,6 & 7.Treble, Middle, Bass & Presence
Passive rotary equalisation circuit. These
interactive controls provide a wide range of tonal
possibilities for both channels.
8. Reverb Control Channel A
Controls the amount of reverb on Channel ‘A’.
9. Master Volume Channel A
Controls the overall volume level of Channel ‘A’.
10. Reverb Control Channel B
Controls the amount of reverb on Channel ‘B’.
11. Master Volume Channel B
Controls the overall volume level of Channel ‘B’.
12. Channel B ‘ON’ Push Switch/LED
Indicates red when Channel ‘B’ is selected
either manually or by remote footswitch (models
P802).
13. Footswitch Jack Socket
Connects the remote dual footswitch (models
P802) for reverb ON/OFF and Channel A/B
switching.
14. Standby Switch
Allows the amplifier to remain at ‘standby’ (i.e.
the valve heaters remain on, ready for instant
use, but without the signal circuit being active).
15. Power Switch
On/Off switch for total mains power to the
amplifier.
1. Effects Loop Level Control
Adjusts the level of the effects loop from -
10dBV to + 4dBm. Higher settings match
modern effects processors and lower settings
match floor pedals.
Note:
Some effects such as distortion and
compression are best suited to connection via
the front panel input as opposed to the loop.
2. Effects Send Socket
Jack socket for connection to the input of
external effects processor.
3. Effects Return Socket
Jack socket for the connection from the output
of external effects processor.
4. Recording Compensated Line-Out
Socket
Jack socket for direct connection to recording
equipment or PA system.The signal is specially
filtered for optimum recording performance.
5. Direct Line-Out Socket
Unfiltered pre-amp signal for connection to
external power amplifiers.
6. Impedance Selector Switch
Two-way switch for matching the amplifier to
speaker impedance. Amp heads feature 8 or 16
Ohm operation. Combo versions feature 4 or 8
Ohm options.
7. Loudspeaker Output Jack Sockets
Parallel wired jacks for linking speaker
cabinets. Ensure that the speaker system is
easily capable of handling the full amplifier
power and that the impedance (item 6) is
correctly selected. If in doubt consult your dealer.
8. Output Mode Switch
Switches the amplifier from high to low power
output.The “low” setting configures the output
stage to “triode” operation, which gives half the
rated output (i.e. 25 Watts on 50 Watts models -
or 50 Watts on 100 Watt models).The “high”
power position gives “pentode” operation for the
full rated output.
9 & 10.Valve Failure LED (OPV1-OPV4)
Valve Fuse (OPV1-OPV4)
In the case of output valve failure (OPV1-
OPV4), the fuse (item 10) will operate and
illuminate LED (item 9).The amplifier will
continue to function on reduced power (Using
OPV2-OPV3 Only). Service should be obtained
as soon as possible to prevent the premature
ageing of (OPV2-OPV3).
11 & 12.Valve Failure LED (OPV2-OPV3)
Valve Fuse (OPV2-OPV3)
Similar functions to items (9) and (10) but
operating on OPV2 and OPV3.
13. Mains Power Input
Connects the amplifier to the mains power
supply.
Note:
Always ensure that the incoming mains voltage
matches that of the amplifier. If in doubt consult
your Marshall dealer.
14. Mains Power Fuse
Protects the amplifier and mains supply in the
event of a fault.
Note:
Always ensure that the fuse value matches the
labelling on the amplifier rear panel. If in doubt
consult your dealer.
3 4

ENGLISH

FRONT PANEL FUNCTIONS

REAR PANEL FUNCTIONS

ENGLISH

Manual

View the manual for the Marshall JCM 900 here, for free. This manual comes under the category guitar amplifiers and has been rated by 3 people with an average of a 6.8. This manual is available in the following languages: English. Do you have a question about the Marshall JCM 900 or do you need help? Ask your question here

Need help?

Do you have a question about the Marshall and is the answer not in the manual?

  • Receive updates on solutions
  • Get answers to your question

Question and answer

Number of questions: 2
P
paul chumleyAugust 16, 2023

I have aJCM900 4501 combo. Speaker Celestion G12T75. What is the impedance of the speaker, please? Which setting do I switch the impedance (i.e. 8 or 4(16).

G
GregNovember 11, 2023

what order do mixed matched power tube amps go in

Marshall JCM 900 specifications

Below you will find the product specifications and the manual specifications of the Marshall JCM 900.

The Marshall JCM 900 guitar amplifier is a highly regarded amplifier known for its powerful and versatile performance. It is designed to deliver a rich and dynamic sound that suits a wide range of musical styles. The JCM 900 features a solid construction, ensuring durability and longevity. It is built with high-quality materials that contribute to its reliability and robustness. Equipped with a range of controls, this amplifier allows musicians to customize their sound to their liking. It offers various tone-shaping options including gain, bass, middle, treble, and presence controls. These controls enable precise adjustment of the amplifier's sound characteristics, allowing musicians to achieve the desired tone. The JCM 900 produces a significant amount of power, making it suitable for both small studio sessions and larger live performances. It is equipped with multiple input and output options, providing flexibility for connecting to external devices such as effects pedals or recording equipment. The amplifier's design is simple and straightforward, making it easy to operate. It offers a reliable and consistent performance, allowing musicians to focus on their music without worrying about technical issues. Overall, the Marshall JCM 900 guitar amplifier is a highly capable and reliable amplifier that delivers excellent sound quality. It is a popular choice among musicians looking for a versatile and powerful amplifier to enhance their performances.

General
BrandMarshall
ModelJCM 900
Productguitar amplifier
LanguageEnglish
FiletypeUser manual (PDF)

Frequently Asked Questions

Can't find the answer to your question in the manual? You may find the answer to your question in the FAQs about the Marshall JCM 900 below.

Why is my Marshall JCM 900 not producing any sound?

Make sure the power switch is turned on, verify that all cables are securely plugged in, and check that the volume and gain knobs are properly adjusted.

How can I achieve a higher volume level from my amp?

Increase the master volume control, while also adjusting the individual channel's volume knobs to find the desired balance.

What should I do if my guitar tone sounds distorted or muddy?

Try reducing the gain or overdrive settings, adjust the equalizer settings to enhance clarity, and ensure proper speaker impedance matching.

What is the purpose of the effects loop on the amp and how do I use it?

The effects loop allows you to connect external pedals or rack-mounted effects. Simply connect the send and return jacks correctly, making sure the effects are active and properly adjusted.

How can I safely switch between different speaker outputs on my amplifier?

Ensure the amplifier is powered off before connecting or disconnecting speakers. Make sure the impedance selector is properly set for the speakers used and avoid using a lower impedance than recommended.

Is the manual of the Marshall JCM 900 available in English?

Yes, the manual of the Marshall JCM 900 is available in English .

Is your question not listed? Ask your question here

No results