Faq & troubleshooting guide – Marshall Amplification MF350 User Manual

Page 8

background image





Can I use the MF350 power amp with another pre-amp?

Yes, follow these simple steps:
Connect the output of your pre-amp to the MF350 FX RETURN jack socket.
Turn GAIN to MINIMUM on AMP 1 and AMP 2
Turn the FX LEVEL to maximum on AMP 1 and AMP 2
Insert a jack plug into the INPUT jack socket to release the automatic muting facility.
Note: You can use the footcontroller to select either the AMP 1 or AMP 2 power amp


Can I connect any cabinet to my MF350 head?

Yes, so long as the total impedance into the amplifier is equal or more than 8 Ohms (check the

impedance selector on your cabinet). Please be aware that the MF350 can deliver 350 Watts and if,
for example, your cabinet is only rated 280 Watts, there is a chance that you might damage your
speakers by playing at high volume.

Can I run my amp without a speaker cabinet connected, while doing silent recording for

Yes, unlike a valve amplifier the MF350 allows you to do this. We recommend however that you

turn the MASTER VOLUME to minimum, as it does not affect the output level on the EMULATED

What does emulated out mean?

This means that the line output is emulating the sound a good quality microphone located in front

of your cabinet would produce. This allows you not only to record silently, but also provides an easy
and reliable way of getting a good sound through a P.A.

Can I use headphones in the EMULATED LINE OUTPUT?

No, the LINE OUTPUT is a mono signal, whereas you would need a stereo output for


Where is the best place for connecting my effects, front end or in the effects loop?

Please refer to the section entitled Parallel to Series Effects Loop (page 8) for detailed


What instruments can I use with my amplifier?

The MF350 has been designed for use with an electric guitar, including baritone and detuned


Can I disconnect the fans for recording when using the speaker cabinet mic’ed up?

No, there are no user servicable parts in the MF350 and the fans are extremely important for the

reliability of this product. The fans are the quietest available, but if you want to minimise any
residual fan noise during your recording we recommend applying the favourite studio technique of
buying a long speaker lead and connecting the head in a different room to where the cabinet is
mic'ed up.

What would happen if I connected a single 16 Ohm speaker cabinet to loudspeaker output II
of the Mode Four?

No damage would be caused connecting a single 16 Ohm cabinet to output II or connection of a

single 8 Ohm cabinet to output I. However, the damping would be mismatched and this would have
a negative effect on the sound.

TONE TIP: Damping refers to the amount of feedback applied to the power amplifier of the MODE

FOUR from the speakers. It is important the damping is correctly matched to the load impedance
used for optimum sound.


CIRCUIT active – the
red LED will be lit on
the back of the unit

Microphonic (i.e. loose)

Acoustic feedback

Reverb Footswitch is

Minimum impedance
not respected

Ensure the mains power cord is correctly connected to
the rear of the unit and then plug the power cord into
the wall outlet securely.

Ensure the MF350 is correctly connected to the mains
supply and turn the ON/OFF button to the ON position.
Wait 30 seconds for the valves to warm up.

Make sure that all Gain, Volume and Master Volume
controls are not on zero (also ensure that the guitar
volume is up!)

Ensure your guitar lead is inserted fully at both ends
and that the lead isn’t damaged. It is always good
practice to have a spare guitar lead.

First turn the MASTER VOLUME down and then turn the
MUTE button off. Slowly increase the MASTER VOLUME.

Disconnect all cables from SEND and RETURN on
the rear panel. If the sound comes back, check your
cables and outboard effects units.

Ensure the speaker cable is in good condition and is
fully inserted into the MF350 and the speaker cabinet.

Switch the amplifier off and check the total minimum
impedance of your speaker cabinet(s) and that your
speaker cable is correctly connected. Turn the MF350
on, if the problem is solved the red LED will be off.

Contact a qualified guitar technician for more

Increase the distance/orientation between the speakers
and the guitar pickup, or alternatively decrease the
gain or volume of the amplifier.

Ensure the red LED above the REVERB switch on
the supplied footcontroller is on.

Ensure the minimum impedance of your speaker(s)
configuration is not below 8 Ohms; please refer to the
Cabinet Options guide on page 10.


No power

The mains power cord
is disconnected.

No sound

Power is off

Volume control off

Guitar lead

MUTE Switch is on
(amber light is on)

Direct signal in FX LOOP
is interrupted while the
FX LEVEL is on full

Speaker cable is

Low frequency feedback

High frequency
feedback and ‘squeals’

No Digital Reverb even
with the level control on

ACTIVE LED is on and
the sound stops while


Before calling the service department, check the following:

If the unit does not seem to operate properly, read the instructions again, then check the table

below. Under no circumstances should you attempt to repair an amplifier yourself, as this could be
dangerous and would void the warranty.

Frequently Asked Questions

Troubleshooting Guide