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5—13 

5.4.4  Ventilator control 

The  control  of  the  cooling  ventilator  is  based  on  the  temperature  of  the  power  stage’s  heat  sink.  It 
automatically switches itself on when the temperature reaches 60°C and switches itself off when temper ature 
decrease below 50°C. 
Do not cover the ventilation cutouts! 

5.4.5  Limiter 

This  function  protects  the  power  section  against  distortion.  When  it  detects  distortion  on  the  output, 
decreases  the  input  signal  of  the  power  stage.  In  practice,  there  is  no  significant  distortion  on  the  power 
stage when you overdrive it, the system will only lose some of its dynamics. 

5.4.6  Phantom power 

You can activate the phantom power function in the amplifier to supply your active bass electronic connected 
to Active input. So you do not need a battery in your bass. 
Requirements: 

stereo instrument cable 

activate  the  phantom  power  by  the  DIP  switch  located  on  the  bottom  of  the  amplifier.  The 
settings are described in section 5.4.7. 

if your electronic does not support phantom power, you have to disconnect the battery and make 
a short circuit on the battery clip in the bass. 

 
Note: 
The phantom power can supply 14.5V and max. 6mA. You get more headroom compared to the use of one 
9V battery before. Make sure that your electronic circuit can handle more voltage than 9V. If not, you can set 
only 9V on the DIP switch. 
 
Warning: 
If you use this function, pay attention that you Mute the amplifier before plug in or out the instrument cable. 

5.4.7  DIP switches 

The DIP switches are located on the bottom of the amplifier. You can set these functions: 
 

1.  if ON, the Boost channel can be activated by the first button of the Foot Switch 
2.  if ON, the Shape can be activated by the first button of the Foot Switch 
3.  if ON, this activates the phantom power 
4.  if ON, the phantom power supplies only 9V instead of 14.5V 

 
Note: 
If both switch 1. and 2. are ON, then you can switch on both of the Boost channel and Shape

Summary of Contents for KO750

Page 1: ...PROLUDE AMPLIFICATION KO750 KO750 KO750 KO750 Bass amplifier User s manual ...

Page 2: ...1 2 ...

Page 3: ...IC PRECAUTIONS 2 5 2 2 WARNINGS USED ON THE AMP 2 5 2 3 GROUNDING INSTRUCTIONS 2 5 2 4 CE MARK FOR EUROPEAN HARMONISED STANDARDS 2 5 3 SPECIFICATIONS 3 6 4 INFORMATION FOR INSTALLING 4 7 5 CONTROLS AND FUNCTIONS 5 8 5 1 THE FRONT PANEL 5 8 5 2 REAR PANEL 5 11 5 3 BLOCK DIAGRAM 5 12 5 4 OTHER FUNCTIONS PROTECTIONS 5 12 6 MAINTENANCE CLEANING 6 14 ...

Page 4: ...ape and role within the music have all contributed to my enthusiasm To start with my studies and my sphere of interest have both moved me to the direction of electronics As a result PROLUDE AMPLIFICATION was born at the beginning of the new millennium My goal is to provide bass players with the best possible sound quality Being an electrical engineer I m doing it mainly with a technical mindset Ho...

Page 5: ...l servicing should be referred to qualified service personnel 11 For continued protection against the risk of fire replace fuses only with those of the same type and rating 2 2 Warnings used on the amp The lightning flash with the arrow head symbol within an equilateral triangle is intended to alert the user to the presence of uninsulated dangerous voltage within this product s enclosure that may ...

Page 6: ...aker output connectors Neutrik Speakon Jack combo NLJ2MD H Instrument input connectors Neutrik 6 3mm Jack NMJ4HFD2 Input impedance Passive 500kohms Active 43kohms FX Return 15kohm Active Equalization Low 12dB 40Hz Low Mid 12dB 500Hz Mid 12dB Mid freq 800 3200Hz High 12dB 6kHz shelving type Line out 500mVp 600Ohms Phone 1 5Vp 50Ohms Working temperature range 0 40 C Storage temperature range 25 60 C...

Page 7: ...aker cabinets Use high quality Neutrik SPEAKON SPEAKON speaker cable with at least 2x1 5mm2 or more cross section They are reliable robust and have less influence on the sound Use a speaker cable in good condition and connect the speaker cabinet to the amplifier before you switch on the amplifier Try to minimize the number of power strips used to connect the amplifier to the mains Use high quality...

Page 8: ... will not cause any problem In such a case you get a larger signal level with some drive In some situations this can sound good At this point you have to consider the power handling of your speakers because the overdriven sound strains them more If you set the Gain too low the preamp section will not send enough signal to the power stage and the output power may be not enough and may also detain t...

Page 9: ...Out If the button is pressed the red LED is bright Note This Mute LED gives you additional information too see section 5 1 16 5 1 11 Phone Phone output drives stereo headphones in mono mode Its volume can be controlled by the Gain potentiometer 5 1 12 Foot Sw Footswitch input You can connect a two buttons footswitch here via a stereo jack cable You can activate the Boost channel or Shape function ...

Page 10: ... speakers connected It is normal Important Please avoid switching on and off the amplifier too often especially after playing at high volume level After playing at high volume level give the ventilator a few minutes to cool down the amplifier before switching it off 5 1 15 Mute LED Multifunctional feedback LED Bright when the Mute button is pressed Or if unpressed after switching on during the ven...

Page 11: ...if you have one instead of jack Avoid long speaker cables and low quality plugs in order to maintain sound quality and volume The amplifier can be used without speakers as well Warning There is dangerous voltage on the speaker output Connect the cabinets to the amplifier before switching on and do not touch the hot pole of the speaker jack 5 2 3 Ventilation cutouts Do not cover the ventilation cut...

Page 12: ...ventilator fault or too high environment temperature while playing at high volume overheating may occur In such a case the protection circuit detaches the speaker cabinets until the temperature of the power stage cools down This is being displayed by the Mute LED Input stage Preamp Boost Shape Comp Speaker Prot Volume Control Power Amp Level Det Line Buffer Phone Amp Fan Control Active Passive Act...

Page 13: ...he DIP switch located on the bottom of the amplifier The settings are described in section 5 4 7 if your electronic does not support phantom power you have to disconnect the battery and make a short circuit on the battery clip in the bass Note The phantom power can supply 14 5V and max 6mA You get more headroom compared to the use of one 9V battery before Make sure that your electronic circuit can...

Page 14: ...he amplifier has no need for particular maintenance Occasionally check the starting of the ventilator when you switch on the amplifier Use only soft and dry or dampened cloth for cleaning Avoid aggressive caustic cleaning materials ...

Page 15: ...6 15 Budapest 2014 03 27 ...

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