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OWNERS MANUAL

MODEL 801

MICROPHONE PREAMPLIFIER

PO Box 204 Boulder, CO 80306 303.443.7454 fax: 303.444.4634

http://www.gracedesign.com

Revision C December, 1999

© Copyright 1996, Lunatec LLC

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Summary of Contents for m801

Page 1: ...OWNERS MANUAL MODEL 801 MICROPHONE PREAMPLIFIER PO Box 204 Boulder CO 80306 303 443 7454 fax 303 444 4634 http www gracedesign com Revision C December 1999 Copyright 1996 Lunatec LLC ...

Page 2: ...ONS 5 1 DC power cord 5 2 DC power cord connect sequence 5 3 Power Supply Location 5 4 AC power cable 5 5 AC input voltage 5 a Fuse table 5 C GROUNDING OPTIONS 6 1 Ground switch 6 D MOUNTING 7 E MAINTENANCE 7 1 PEAK LED ADJUSTMENT PROCEDURE 7 2 EQUIPMENT NEEDED 7 3 PROCEDURE 7 F INPUT OFFSET ADJUSTMENT 10 1 EQUIPMENT NEEDED 10 2 PROCEDURE 10 3 SPECIFICATIONS 12 4 SCHEMATIC DIAGRAMS 13 A Gain Switc...

Page 3: ...nd refinement We hope it helps you achieve a new level of excellence 1 OPERATION A FRONT PANEL CONTROLS 20 48V O 48V O O 20 48V 20 48V O 20 GAIN CONTROL 20dB ATTENUATOR PEAK INDICATOR PHASE REVERSE MEMO STRIP PHANTOM POWER Figure 1 Front panel controls 1 GAIN CONTROL Each gain control has 24 positions and adjusts the voltage gain from 18dB to 64dB in 2dB steps For reference the 9 o clock position ...

Page 4: ...lanced mode The threshold level for peak indication is adjustable on each channel See section V Maintenance 6 MEMO STRIP The Memo strip can be used with dry erase or wet erase type markers If using dry erase markers black is recommended Grease pencils are not recommended B SETTING THE GAIN 1 Turn the gain control fully counter clockwise and check that the 48V phantom power is off Connect the micro...

Page 5: ...ch produces a positive voltage on pin 2 with positive air pressure on the front of the diaphragm While a vast majority of microphones conform to this standard a few do not Use the phase reverse switch to compensate if necessary Figure 2 Unbalanced output cable termination 3 The balanced output driver is capable of driving a matched 600Ω line This type of termination can be very advantageous for dr...

Page 6: ...cord be connected to a grounded outlet In the event of noise from a ground loop the audio ground can be isolated from the chassis ground by removing jumper J9 in the power supply See paragraph 6 5 AC input voltage settings can be adjusted for 100V 120V 220V and 240V operation at 50 60Hz From the rear of the power supply unit open the trap door next to the IEC power inlet with a small screwdriver C...

Page 7: ...et the AUDIO GND toggle switch on the rear panel of the power supply unit to the desired setting ISO or EARTH To isolate the audio ground from the chassis ground on 801 preamplifiers with serial 81030 and below use the following procedure i Unplug the power supply unit from AC power ii With a No 2 phillips screwdriver remove 9 6 power supply top cover screws and remove cover iii Locate J9 and remo...

Page 8: ...hreshold at 14dBu and the red threshold at 16dBu The relationship between the two thresholds is fixed The procedure for adjusting the red threshold follows 2 EQUIPMENT NEEDED i Sine wave audio signal generator or oscillator output from a mixing console ii Audio level meter or VTVM with dBu or dBm scale iii Plastic alignment tool or small screwdriver iv Appropriate interconnect cables v 3 32 hex wr...

Page 9: ...rial 81036 and below Adjust VR1 until the peak LED is between green and red The color should appear amber when the setting is correct vii Repeat this procedure for channels 2 through 8 viii If it is desired to calibrate the peak indicator to a specific tape disk recorder input level simply connect the output of the preamplifer to the tape disk recorder Adjust the signal generator so that the desir...

Page 10: ...Page 9 Figure 7 Peak LED Adj VR1 and Offset Adj VR2 for serial 81037 and above Figure 8 Peak LED Adj VR1 and Offset Adj VR2 for serial 81036 and below ...

Page 11: ...ecause the gain control being a stepped control will make an instantaneous change in amplitude when turned which creates a transient signal 1 EQUIPMENT NEEDED i Oscilloscope with a DC coupled 10mV input range ii Unbalanced output cable see Figure 1 iii Plastic alignment tool or a small screwdriver iv 3 32 hex wrench 2 PROCEDURE i Remove the 9 8 32 flat head screws from the top lid but leave the li...

Page 12: ...tly to the zero line What is important here is the relative offset between low and high gain settings Turn the gain control quickly between minimum and 12 o clock then back to minimum and watch the change in offset Adjust VR2 so that the trace stays still while turning the gain up and down This step provides a coarse adjustment To make a fine adjustment repeat this step but turn the gain control a...

Page 13: ... 60dB gain 50 Ω source 130dB PHASE DEVIATION 50 20KHz 2 CROSSTALK Any Channel 109dB CMRR 60dB gain 3 5Vcm 1KHz 80dB 60dB gain 3 5Vcm 10KHz 97dB Output CMRR 60dB MAXIMUM OUTPUT LEVEL Balanced 28dBu Unbalanced 22dBu IMPEDANCE Input 1600Ω Output 150Ω Minimum Load Impedance 50Ω WEIGHT 12lbs DIMENSIONS 2U rack mount x 10 deep POWER SUPPLY SPECIFICATIONS POWER CONSUMPTION 120VAC 60Hz 40 Watts max WEIGHT...

Page 14: ...Page 13 4 SCHEMATIC DIAGRAMS A Gain Switch Assy B Switch PCB Assy C Power Supply PCB D DC Input PCB E DC Power Cable F Audio PCB Assy ...

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