background image

 
 
 

 

 

 

 

All

Discrete

  

4

Channel

 

Mic/Instrument

 

Preamplifier

  

with

 

Stereo

 

Mixer

 

Operator’s Manual 

 

Written by Carl J Houde 

2015 

 

 

Summary of Contents for 3124mb+

Page 1: ...3124mb All Discrete 4 Channel Mic Instrument Preamplifier with Stereo Mixer Operator s Manual Written by Carl J Houde 2015 ...

Page 2: ...s 8 4 3 Input Selection 9 4 3 1 MIC Switch 9 4 3 2 Microphone Input 9 4 3 3 Instrument Input 10 4 4 Polarity Inverter 10 4 5 VU Meter 10 4 6 Direct Output 10 4 7 Preamplifier Block Diagram 11 5 0 Output Section Stereo Mixer 12 5 1 Stereo Mixer Overview and Features 12 5 2 Stereo Mixer Controls 12 5 2 1 Masters 12 5 2 2 Auxiliary Level 12 5 2 3 Auxiliary Return Pan 13 5 3 Stereo Mixer Block Diagram...

Page 3: ... will explain how and why each feature can be used in a professional project or home studio Each of the 3124mb preamplifier and stereo mixer parameters is covered Included are signal flow schematics and block diagrams that may help troubleshoot any issues that arise when using the 3124mb After reading this operator s manual you will be armed with all the necessary knowledge to efficiently use the ...

Page 4: ...ich is front panel switchable for each channel Also provided is a front panel 20dB pad switch that affects both the rear mic in and front Hi Z in A phone jack is available on the rear panel for each channel as an insert tip send ring return placed between the mic preamp output and the mixer input Like the 3124 the 3124mb provides up to 65 dB of gain to an output clip level of 28dBu The Hi Z front ...

Page 5: ...e insert device This can be useful for adding signal processing to an individual channel 3 2 2 Auxiliary Send Return AUXILIARY functions are controlled from the 3124mb front panel Each channel has its respective AUX knob which control how much of a channel s signal is being sent to the AUX bus The summed AUX signal can then be sent and returned to an external signal processor via independent TRS c...

Page 6: ...at illustrates signal flow through each preamplifier channel of the 3124mb Understanding the signal flow through each preamplifier channel will help develop a better understanding of how and when each channel s parameters can be used Figure 3 Preamplifier Signal Flow ...

Page 7: ...hat illustrates signal flow through the stereo mixer section of the 3124mb Understanding the signal flow through each preamplifier channel will help develop a better understanding of how and when each channel s parameters can be used Figure 4 Stereo Mixer Signal Flow ...

Page 8: ... character that made it so much a part of the early days of recording Offering high headroom and a wide variety of inputs and input access points each preamplifier is equally at home in the commercial recording studio as it is in the home project studio Features Uses API 2520 Op Amp XLR Mic Input Unbalanced Input Front Panel Polarity Switch Front Panel 20 dB Pad Switch Front Panel Mic Switch Front...

Page 9: ... input by pressing the MIC switch and a green LED should turn on above the MIC switch The MIC input connection on the rear panel will be the active input Female XLR microphone input 48V phantom power 20 dB pad Green LED illuminates when MIC switch engaged VU meter indicates level of preamplifier output 48V Provides 48 volt phantom power to the MIC input female XLR connector Red LED above switch il...

Page 10: ...s referred to as a phase reverse is available at the input of the preamplifier POL Polarity Inverts the polarity of the signal at the input of the preamplifier Yellow LED above switch illuminates when engaged 4 5 VU Meter The preamplifier outputs can be monitored via the VU meter in each input section 4 6 Direct Output Each preamplifier s output is available at its respective OUTPUT connection on ...

Page 11: ...hat illustrates signal flow through each preamplifier channel of the 3124mb Understanding the signal flow through each preamplifier channel will help develop a better understanding of how and when each channel s parameters can be used Figure 7 Preamplifier Signal Flow ...

Page 12: ...High headroom 28 dB clip level Traditional API fully discrete circuit design API 2520 discrete op amp with transformer output 5 2 Stereo Mixer Controls The Stereo Mixer provides a comprehensive suite of controls LEFT Master level for left channel RIGHT Master level for right channel AUX Auxiliary return level RET PAN Auxiliary return pan 5 2 1 Masters LEFT RIGHT Main output faders Full attenuation...

Page 13: ...ignal mixed with main output 5 3 Stereo Mixer Block Diagram Figure 10 shows a block diagram that illustrates signal flow through the stereo mixer section of the 3124mb Understanding the signal flow through each preamplifier channel will help develop a better understanding of how and when each channel s parameters can be used Figure 10 Stereo Mixer Signal Flow ...

Page 14: ...aces 6 1 Audio Path Inputs 6 1 1 Front panel 6 1 2 Rear Panel 6 2 Audio Path Outputs 6 2 1 Rear Panel Figure 11 Front Panel Input Connections Figure 12 Rear Panel Input Connections Figure 13 Rear Panel Output Connections ...

Page 15: ...tch Selects operating voltage 115 volts 230 volts The fuse holder is located on the rear panel 0 5A 0 25A 250V The AC power switch for the 3124mb is located at the lower right of the API logo on the front panel A blue LED indicator illuminates when the unit is on 8 0 Customer Support For further information and inquires please contact API s customer support Call us at 301 776 7879 Fax us at 301 77...

Page 16: ...oise EIN Mic 129 Unbalanced Actual 129 Measured Noise Better than 91 dBm Below Nominal 4 Distortion All Outputs at 4 Out 0 03 All Outputs at 22 Out 0 09 Gain Range 150 Ω Input 10 dB Min 65 dB Max Incl PAD Unbalanced Input 14 dB Min 50 dB Max VU Meter Calibrated for XLR Outputs OVU 4 dBu 12 6 3 0 3 6 18 Controls GAIN PAD 20 dB 48V Volts POL Polarity MIC Mic Unbalanced VU AC Power Consumption Quiesc...

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