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FiveFish X-12 User Manual

Mic preamp kit
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X-12 Mic Preamp Kit
Solid State, Discrete OpAmp Mic Preamplifier
with Input and Output Transformers
Simplicity Counts, Detail Matters.
No part of this document may be reproduced, either mechanically or electronically, posted online on the Internet,
in whole or in part, without the expressed, written permission of FiveFish Studios. This document is solely provided
to the kit builder of the X-12 Mic Preamp Kit.
Document Revision 1.4
Last Update: Oct 16, 2010
Copyright © 2010 FiveFish Studios
www.fivefishstudios.com

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Summary of Contents for FiveFish X-12

  • Page 1 No part of this document may be reproduced, either mechanically or electronically, posted online on the Internet, in whole or in part, without the expressed, written permission of FiveFish Studios. This document is solely provided to the kit builder of the X-12 Mic Preamp Kit.

  • Page 2: Mic Preamp

    Input and Output Transformers Congratulations and thank you for your purchase of the X-12 Mic Preamp Kit. The X12 Mic Preamp is my version of a classic preamplifier circuit made popular in the 70s. Some people call it the “L.A. Sound”, referring to the huge mixing consoles used by L.A.
  • Page 3 X-12 Mic Preamp Variations (Using Discrete OpAmps) The X-12 Mic Preamp has provisions for using discrete opamps if the user so desired. It uses the standard API 2520 OpAmp package and pin-footprint. Many compatible 2520 opamps can be used with the X-12 board. These are also sometimes called 990 OpAmps, or Discrete OpAmps.
  • Page 4 Shown with an APP10 Discrete OpAmp from Italy. Shown with a Melcor 1730 DIY Discrete OpAmp. These are just a very small sampling of what Discret OpAmps you can use with the X-12 Preamp Kit. Copyright © 2010 FiveFish Studios For comments &...
  • Page 5 Page 4 X-12 Microphone Preamp Kit Features, Advantages and Benefits of the X-12 Mic Preamp Uses High-Nickel Mic Input Transformer with MuMetal Shielding Uses Output Transformer for additional 6dB gain and balancing duty 12-step Gain control from +22 to +66dB, in 4dB increments...
  • Page 6 Page 5 X-12 Microphone Preamp Kit Manual Solder sucker pump or desoldering gun– sucks up solder when you made a mistake soldering components on the PCB. Pictured below is a Hakko model. Multitester – A simple meter/tester to measure resistance, and voltages. A digital read-out is a big help.
  • Page 7 3x more expensive than another equivalent part. Resistors All resistors used in the X-12 Kit are 1/4 watt resistors. All of them are 1% tolerance, Metal-Film type resistors. These are high quality resistors, way much better than carbon composition type resistors (which usually 10-20% tolerance).
  • Page 8 RF Interference. This switch will be the most commonly used/abused mechanical device on the X-12 preamp. I want this part to withstand being turned and turned and turned and is just one of the expensive parts in this kit.
  • Page 9 Bandwidth. Output circuitry is fully protected by internal current limiting and thermal shutdown. IC3 is used as a dedicated line driver for the X-12 Mic Preamp. Above is a photo showing the locations of IC1, IC2 and IC3. Note the proper orientation of the chips.
  • Page 10 Page 9 X-12 Microphone Preamp Kit USING DISCRETE OPAMPS You may also use discrete opamps instead of the supplied PDIP8 opamp chip in the kit for IC1. Whether discrete opamps (DOA) are better than today’s current IC chip designs is up for debate. Let your ears (and pockets) decide.  Either way, there is provision on the board to use either discrete opamp or PDIP8 chips.
  • Page 11 Failure to follow this orientation will result in the relay not working, and possibly damaging the relay too. VU METER BOARD The X-12 preamp kit includes a 5-LED VU Meter kit for some basic metering. This is also useful for gauging the strength of the signal and if there is any signal present during troubleshooting.

  • Page 12: Output Transformer

    Page 11 X-12 Microphone Preamp Kit INPUT TRANSFORMER The Input Transformer we’re using provides impedance matching, signal isolation, and “flavor enhancement” to our signal. It’s a High-Nickel Input Transformer with Mu-Metal shielding. Note: There is a resistor R2/RLS near the Input Transformer. This is a loading resistor. Changing this value will allow you to experiment with the sound of the unit.

  • Page 13: Voltage Regulator

    Page 12 X-12 Microphone Preamp Kit NULL OFFSET TRIMMER I provided a trimmer resistor to allow you to trim any output offset voltage to 0V or as close as possible to 0V. One may not be able to achieve exactly 0.00Volt trim, but it’s possible to get it close to less than 1mV of offset.

  • Page 14: Parts Kit

    Page 13 X-12 Microphone Preamp Kit X-12 Parts Kit I’ve taken the time to individually package and label every component used in the kit. Just read the part # printed on the zip bag. Some bags will contain 2, 3 or 5 different components. Other bags will contain just one part#. I want you to be able to build this kit, without sorting through hundreds of parts and not know what to do.

  • Page 15: Assembly Guide

    Page 14 X-12 Microphone Preamp Kit X-12 Assembly Guide The general guideline in electronics assembly is to solder the smallest/shortest component first (resistors, diodes, inductors), and solder the bigger/taller components last (ceramic capacitors, electrolytic capacitors, switches, etc). The last step is inserting the IC chips into the board.
  • Page 16 Page 15 X-12 Microphone Preamp Kit STEP 3: Solder all IC sockets and Relays to the PCB. Make sure to mount all IC sockets in the correct orientation. (This will serve as a reminder on how IC chips will be inserted.) TIP: Use masking tape to hold the IC sockets in place while soldering.
  • Page 17 Page 16 X-12 Microphone Preamp Kit STEP 7: Solder the (3) Push button switches. This switch has 8 legs. They will “snap-in” to the holes in the PCB. Push firmly down until you hear it snap-in. STEP 8: Solder the Bourns potentiometer. Solder the middle leg first, check alignment, and then solder the 2 outer legs.
  • Page 18 Page 17 X-12 Microphone Preamp Kit Build Notes: a. Solder one of the end pins of the Grayhill switch, and then check if the switch is still flushed to the board, straight and not crooked. . If crooked, re-heat the pin and straighten the Grayhill switch while the solder is melted. (DO NOT STRAIGHTEN THE COMPONENT AFTER THE SOLDER BECOMES HARD.
  • Page 19 Page 18 X-12 Microphone Preamp Kit STEP 11: Install the Input Transformer. For the Input Transformer, orient the “dot” with the printed silkscreen dot on the PCB. Don’t forget to also install the R2/RLS resistor located on the lower left corner of the Input Transformer.
  • Page 20 Page 19 X-12 Microphone Preamp Kit STEP 12: Install the Output Transformer. Cut and trim the wires and solder the corresponding wire color to it’s corresponding hole on the PCB board. Mount the Input Transformer using the supplied nuts and bolts.
  • Page 21 Page 20 X-12 Microphone Preamp Kit NOTE: You may want to do STEP 13 LAST, after adjusting the voltages on the X-12 board. This is to prevent damage to the IC chips in case the voltage is too high before adjustments.
  • Page 22 You need to install a jumper wire across the HORIZ position. See photo below. NOTE: VU Meter is installed upside down, bottom side up. (Especially important if you’re using the X-12 Rack Case). NOTE #2: Take note of the LED Color Order for Horizontal Mounting of the preamp board. See guide below.
  • Page 23 Page 22 X-12 Microphone Preamp Kit VU Meter Calibration Guide 1. Adjust trimmer resistor so that when you feed a 0dB signal to the VU Meter, the 3 LED lamp lights up. For +4dBu operation, connect a signal generator to the VU meter input, 1Khz, adjust output of Signal generator to 1.22Vrms, and adjust trimmer resistor until 3...
  • Page 24 No part of this document may be reproduced, either mechanically or electronically, posted online on the Internet, in whole or in part, without the expressed, written permission of FiveFish Studios. This document is solely provided to the kit builder of the VU-1MK500 VU Meter Kit.

  • Page 25: Voltage Adjustments

    After wiring the power supply, we’ll need to make voltage adjustments. I recommend that your power supply board be set to +21Volts or higher. The X-12 board will regulate this voltage further down to +/-18Volts. See next step for Voltage Adjustment.

  • Page 26: Audio Testing

    Page 25 X-12 Microphone Preamp Kit AUDIO TESTING Connect a dynamic microphone to the input XLRs, connect a monitor speaker to the output XLR, turn power ON, set the gain switch, adjust volume and you should hear sound come out of your preamp.

  • Page 27: Troubleshooting Guide

    Problem: My FET condenser mic works, but the sound is very faint. I only hear the sound at the higher gains. Check that you’re feeding the X-12 preamp with +48V. Some condenser mics will work with voltages as low as 14Volts or 18Volts.
  • Page 28 X-12 Microphone Preamp Kit Page 27 X-12 PCB Component Layout Guide Copyright © 2010 FiveFish Studios For comments & corrections about this guide, please email diy@fivefishstudios.com www.fivefishstudios.com...
  • Page 29 Page 28 X-12 Microphone Preamp Kit X-12 Parts List (1u format) Part Qty Value X-12 PCB Capacitors C1,C2 470pf/50V 47pf/50V C4,C5,C13 47uf / 50V C6,C8,C10,C11,C14,C15,C16, 15 0.1uf / 100V C17,C20,C23,C24,C29,C30 22uf / 63V 220UF/50V Cf, C18,C19 100pf / 50V C21,C22...

  • Page 30: Green Led

    Hex machine screw nuts, Zinc steel, 4-40 Bolts for Output Trafo Phillips pan, Zinc plated steel, 4-40 x 3/8 Hex Spacer for Output Trafo HEX .187X.250 ALUM VU-1B Rev1.2 Meter for X-12 Part Qty Desc 1 Custom PCB VREG1 1 78L18...
  • Page 31 Page 30 X-12 Microphone Preamp Kit X-12 Preamp Errata Some last minute corrections in the assembly instructions. 1 .The new batch of Yellow Push Button switches I got have super bright LEDs. To make the LED brightness match the Green and Blue switches, please USE A 10K RESISTOR FOR THE YELLOW LED current limiting resistor.

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