Musical Fidelity M250 Manuale utente

M250 Amplifier Instructions for Use Page 1 of 8

Issue 4: May 2002

O PERATE PO W ER

MUSICALFIDELITY

M250

MONOBLOC AMPLIFIER

INSTRUCTIONS FOR USE

Thank you for purchasing the Musical Fidelity M250 monobloc power amplifier.

Used properly and carefully, it should give you many years of outstanding

musical reproduction.

Dust regularly with a soft duster or soft brush, but be careful when using

cleaning or polishing agents - they may harm the surface finish.

If you have any questions about your audio system,

please consult your dealer who is there to help and advise.

M250 Amplifier Instructions for Use Page 2 of 8

Issue 4: May 2002

SAFETY INFORMATION

IMPORTANT! (U.K. only)

This unit is supplied in the U.K. with a mains lead fitted with a moulded 13 amp plug.

If, for any reason, you need to cut off this plug, please remove the fuse holder and dispose of

the plug safely, out of reach of children. It must not be plugged into a mains outlet.

The wires in the mains lead supplied with this appliance are coloured in accordance

with the following code:

Green and yellow..............Earth

Blue...............................Neutral

Brown................................Live

WARNING - This appliance must be earthed

As the colours of the wires of the mains lead of this appliance may not correspond with the

coloured markings identifying the terminals in your plug, proceed as follows:

The wire which is coloured green-and-yellow must be connected to the terminal in the plug

which is marked with the letter E or coloured green or green-and-yellow, or by the earth

symbol:

The wire which is coloured brown must be connected to the terminal which is marked with the

letter L or coloured red.

The wire which is coloured blue must be connected to the terminal which is marked with the

letter N or coloured black.

If connecting to a BS1363 plug, a 13 amp fuse must be used.

WARNING:

The M250 is a powerful amplifier and must necessarily supply high voltages

through the loudspeaker terminals. Therefore, to avoid any possibility of an

electric shock DO NOT TOUCH THE SPEAKER TERMINALS when the unit is

being used.

To comply with BSEN60065 safety regulations, the 4mm “banana” plug holes have

been fitted with plastic blanking pieces. Removal of these will invalidate any elec-

trical safety approval of this product.

WARNING:

Any modifications to this product not expressly approved by Musical Fidelity who

is the party responsible for standards compliance could void the user’s authority to

operate this equipment.

M250 Amplifier Instructions for Use Page 3 of 8

Issue 4: May 2002

GENERAL ADVICE

INSTALLATION PRECAUTIONS and USER INFORMATION

Your new M250 power amplifier is designed and built to provide trouble-free performance, but

as with all electronic devices it is necessary to observe a few precautions:

Heed all warnings shown on the back of the product.

Only connect the M250 amplifier to a mains outlet having the same voltage as marked at the

back of the unit.

Always ensure that when disconnecting and reconnecting your audio equipment the mains

supply is switched off.

Position the mains lead and signal interconnects where they are not likely to be walked on or

trapped by items placed on them.

Do not use near water, or place water-filled containers on the amplifier, for example, flower

vases or potted plants. If water does spill into the player, immediately pull out the mains plug

from the wall socket and inform your dealer, who should then check the unit before further

use. Entry of liquid into the amplifier is dangerous, and may cause electric shock or fire

hazard.

Do not place the unit near heat sources such as radiators, direct sunlight or other equipment.

The case of this amplifier can run at high temperatures - operate the unit in a well ventilated

area, and do not touch the side heatsink fins after periods of use at high output power.

Do not remove covers or try to gain access to the inside. There are no internal user adjust-

ments. Refer all service work to an authorised Musical Fidelity agent.

NOTE: Unauthorised opening of the equipment will invalidate any warranty claims.

There are fuses inside the M250 Amplifier. In the unlikely event that one blows, refer the unit to

your audio dealer. Do NOT try to replace the fuse yourself as this will invalidate the warranty.

Dust regularly with a soft duster or soft brush, but be careful when using cleaning or polishing

agents - they may harm the surface finish.

The electronics in modern hi-fi equipment is complex and may, therefore, be adversely affected

or damaged by lightning. For protection of your audio system during electrical storms, remove

the mains plugs and disconnect any aerial lead.

If after-sales service is required, to help your dealer identify the M250 please quote the serial

number located on the rear panel of the unit.

RADIO FREQUENCY INTERFERENCE (R.F.I)

This product has been tested to ensure that its operation is not adversely affected by normal

background levels of R.F.I., and that it does not itself generate excessive amounts of interfer-

ence. However, if a problem persists, please contact your Musical Fidelity agent.

M250 Amplifier Instructions for Use Page 4 of 8

Issue 4: May 2002

CONNECTIONS AND FACILITIES

MADEIN EN G LA N D BY MUSICALFIDELITY

POWER CONSUMPTION 400W

SERIALNUMBER

50/60H z

PO W ER

UNITS 15-17 OLYMPIC TRAD ING ESTATE

FU LTO N RO AD W EM BLEY MID D LESEX HA9 O TF EN G LA N D

IMPORTANT

SPEAKER

OUTPUTS

+CAU TIO N

DO NOTREMOVESC REW S

ORC O VERS UN DER AN Y

CIRC U M STAN C ES.

NO USERSERVICEABLE

COMPONENTSINSIDE.

REFER SE RV ICING TO

QUALIFIED EN G IN EER.

LINE

INPUT

LOOP

OUTPUT

OFF

TRIGGER

OUT

34 56

Front panel layout

1OPERATE indicator LED (blue)

2 Power status button (see page 6)

3POWER-on indicator LED (orange)

Back panel layout

3 Speaker output (see page 5)

4 Speaker output (see page 5)

5 Power switch

6 IEC type mains inlet socket

7 Trigger output (see pages 5 and 6)

8 Audio loop output (see page 5)

9 Audio line input

10 Trigger input (see pages 5 and 6)

O PERATE PO W ER

MUSICALFIDELITY

12 3

78 910

M250 Amplifier Instructions for Use Page 5 of 8

Issue 4: May 2002

CONNECTIONS

Taking the left channel connections, the

pre-amp’s left output is connected to the-

first M250’s LINE INPUT (used for the

woofer, or low frequencies), and then the

first M250’s LOOP OUTPUT is connect-

ed to the LINE INPUT of the second

M250 (used for the tweeter, or high fre-

quencies).

Repeat this process for the right channel.

If you are in any doubt about bi-amping,

please contact your dealer, who will be

able to advise.

TRIGGER CONNECTIONS

Two 3.5mm jack sockets on the rear panel

marked TRIGGER IN and TRIGGER

OUT are provided for electronically

switching the “audio sense” mode - see

page 6. These are directly linked together

inside the amplifier, to enable onward con-

nection to a further unit, such as another

M250.

OUTPUT CONNECTIONS

Connect your loudspeaker to the terminals

marked SPEAKER OUTPUTS.

Two sets are provided for parallel opera-

tion or “bi-wiring”, but note that the

combined load impedance must not be

less than 4 ohms.

BEFORE SWITCHING ON. . . . .

Plug the accessory IEC mains lead into the

rear panel socket, then the other end into a

wall outlet.

Turn the volume control on your preampli-

fier to minimum, and switch on its power.

All input, output and power connections

should be made with the mains power

switched OFF.

INPUT CONNECTIONS

As the M250 is a mono power amplifier,

two are required for stereo operation, and

further units can be used for multi-channel

surround systems or bi-amplification etc.

The M250 can be used with a preamplifier

or any audio line level source which has a

volume control.

Connect your pre-amplifier or other line

level source to the RCA socket on the

back panel marked LINE INPUT.

For the best results we recommend either

Musical Fidelity X-LINX "no-nonsense"

cables for this connection or the highly

rated Nu-Vista leads with integral RFI

suppression. Various lengths are available

in the Nu-Vista interconnect range. Please

contact your local dealer for more infor-

mation.

BI-AMPLIFICATION

The M250 has a LOOP OUTPUT socket

to allow “bi-amping” of a speaker with

suitable active or passive crossover net-

works. This socket is directly linked

inside the amplifier to the LINE INPUT

socket to enable onward connection to a

further unit, such as another M250.

In this arrangement, typically one M250 is

used to drive the “tweeter” (high frequen-

cies), and one to drive the “woofer” (low

frequencies) of each loudspeaker enclo-

sure. Thus, four M250s would be needed

for a stereo pair.

M250 Amplifier Instructions for Use Page 6 of 8

OPERATION

Issue 4: May 2002

OPERATION

Press the POWER rocker switch on the

rear panel - the orange POWER LED on

the front panel will light confirming that

the unit is ready for use.

Audio Sense Mode

The M250 is now in “audio sense” mode,

and will turn on when an input signal is

detected.

When an audio signal is received the

amplifier will turn on, and the blue OPER-

ATE LED will be lit. If there has been no

audio input for about 15 minutes the

amplifier will turn off and the OPERATE

LED will go out.

The M250 may be turned on or off manu-

ally by pressing the power status button on

the front panel.

When the amplifier has been turned on

manually by the front button it will revert

to “audio sense” mode if there has been no

audio input for about 15 minutes.

When the amplifier has been turned off

manually by the button it will stay off,

even if audio input is present, until there

has been no audio for about 15 minutes,

when it will revert to “audio sense” mode.

If there is an audio input signal present

when mains power is applied to the M250,

it will turn on immediately with the

OPERATE LED lit.

Trigger Mode

The M250 responds to a “trigger on” con-

trol voltage of between 5 and 12 volts posi-

tive or negative, received via the 3.5mm

TRIGGER IN socket on the rear panel.

The first trigger pulse received after apply-

ing mains power will turn the amplifier on,

and cancel the “audio sense” mode.

When the amplifier senses a “trigger off”

pulse (return to zero voltage), the amplifier

will turn off.

The M250 may be turned on or off manual-

ly with the front panel button at any time.

When the amplifier has been turned on

manually by the button, it will turn off if it

receives a “trigger on” signal followed by a

“trigger off” pulse.

If the amplifier has been turned off manual-

ly by the button, it will turn on if it receives

a “trigger off” signal followed by a “trigger

on” pulse.

To cancel trigger mode and revert to audio

sense mode, first remove the trigger source.

Then, using the mains switch at the rear of

the unit, turn mains power off and after a

few seconds, back on again.

Audio Adjustment

Select the required audio input source on

your pre-amplifier, and advance the volume

control to obtain the preferred sound level.

M250 Amplifier Instructions for Use Page 7 of 8

Issue 4: May 2002

TROUBLESHOOTING

Basic problem-solving with an amplifier is similar to troubleshooting any other electrical or

electronic equipment. Always check the most obvious possible causes first. To give you a few

ideas of what to look for, check the following:

If none of these actions effect a cure, please contact your dealer, or an authorised Musical

Fidelity service agent. Remember, never open the case of the M250 power amplifier yourself,

as this will invalidate the guarantee.

Problem Possible Cause Remedy

No power when MAINS Mains plug not inserted Plug in securely

POWER switch is operated fully into rear socket

No sound Tape monitor function has Switch off tape monitor

been selected on the pre- at the pre-amplifier

amplifier

Wrong connections between Check audio input lead

pre-amplifier and the M250 connections

Speakers not connected, or Check speaker cables

incorrectly wired

In multi-channel use, the Speakers are connected out of Ensure speakers are

sound is not precise, and phase connected correctly

lacking bass and stereo

image

M250 Amplifier Instructions for Use Page 8 of 8

Issue 4: May 2002

SPECIFICATIONS :

Output voltage, RMS 45 Volts 20Hz to 20kHz

peak 127 Volts

Power output 250 Watts into 8 Ohms (24dBW)

450 Watts into 4 Ohms

Peak-to-peak output current 72 Amps

Damping factor 180

Output devices per channel 6

Total Harmonic Distortion + noise 0.006% at 1kHz up to 90% power, into 4 or 8 Ohms

Intermodulation distortion 0.004% at 12.5 Watts into 8 Ohms

Frequency response 20Hz to 20kHz ±0dB

10Hz to 100kHz +0 / -1.5dB

Audio gain 30dB (31.5 times) nominal

Input impedance 31K Ohm

Input sensitivity for full power output into 8 Ohms 1.42 Volts

Signal / noise ratio, reference full power output > 115dB “A”- weighted

Input 1 RCA connector

Outputs 1 amplifier channel via 2 pairs of speaker binding posts

1 RCA loop output socket

Power requirements 100 / 115 / 230V AC, 50 / 60Hz (factory preset)

1000 Watts maximum into 8 Ohms load

70 Watts idle

Dimensions 192 mm, 7.6 inches wide

125 mm, 4.9 inches high including feet

460 mm, 18.1 inches deep including terminals

Weight 12 kg, 26.4 lbs unit only, unboxed

14 kg, 30.8 lbs in shipping carton

Standard accessories IEC type mains lead

Musical Fidelity reserves the right to make improvements which may result in specification or feature changes without notice.

M250

Monobloc Amplifier

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