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NK-72DI Mic DI Assembly Guide

10. TROUBLESHOOTING GUIDE

Hey, we’re all human and make mistakes. Hopefully the tips below will help you troubleshoot your Mic Preamp build.

When I turn the gain knob clockwise, the sound decreases instead of increasing. At minimum gain setting, I have a very loud output signal.

It’s backwards!

Please review Step 3.19 and look closely at how the wires are connected to the potentiometer. You need to swap the location of your 2 wires if your

gain is backwards.

I hear a popping sound when I switch from DI Instrument to Mic Input. I’m using a Condenser microphone with 48Volt phantom power

switched ON.

Turn OFF 48V Phantom Power switch and wait a few seconds before switching between DI Instrument and Mic Input or vice versa. Otherwise, you

may get a popping sound if you switch between the (2) inputs, AND have 48V Phantom Power turned ON.

Summary of Contents for NK-72DI

Page 2: ...cally posted online on the Internet in whole or in part without the expressed written permission of FiveFish Audio This document is solely provided to the kit builder of the NK 72DI Mic Preamp Copyright 2016 FiveFish Audio fivefishaudio com Assembly Guide Revision 1 1 20160530 ...

Page 3: ... This assembly guide is a work in progress and we re continually working to improve it As always we welcome the input of the DIY community if you have any comments suggestions or additional information that you think will be helpful for inclusion in this assembly guide If you have any questions that are not covered by this assembly guide please feel free to contact us at www fivefishaudio com or v...

Page 4: ...rsonal injury Grounding one conductor of a two conductor outlet is not sufficient protection This mic preamp module is designed to be plug in into an API 500 series rack or compatible unit DC Power is supplied by the 500 series rack to this module It is strongly suggested that you use a lab power supply the first time you power your mic preamp project If you made any mistake during assembly of thi...

Page 5: ...e microphones This soft start approach also prevents the typical sudden popping noise when phantom power is turned ON The NK 72DI uses switched relays with separate push button controls for 48V Phantom Power 20dB Pad Polarity Reverse and Mic DI Input selection The kit builder can also wire optional 3mm LED indicators for each switch to indicate when the function is enabled The NK 72DI also feature...

Page 6: ...mall to medium sized soldering tip is required to solder the small parts You may use Lead free or 60 40 lead based solder 2 2 Cutter You will need a cutter to cut component leads and wires 2 3 Solder Sucker Pump If you made a mistake and need to desolder a component you ll need one 2 4 Multitester Used for measuring resistance continuity and voltages 2 5 Magnifier Lamp I recommend a clean and well...

Page 7: ...enience The labeled components lessens chances of insertion errors inserting the wrong component into the wrong location Keeping the components in their zip bags also reduces chance of small parts getting lost or misplaced The best practice is to solder the smallest and or shortest components first Then solder the taller and larger components next Big bulkier components like switches jacks big cap...

Page 9: ...io NK 72DI Mic Preamp DI Assembly Guide 3 2 Solder all Diodes IMPORTANT Diodes must be installed in the correct orientation Observe location of the white band on the board silkscreen and orient Diodes to follow the same direction ...

Page 11: ...yright 2016 FiveFish Audio NK 72DI Mic Preamp DI Assembly Guide 3 4 Solder the 6 Mill Max Sockets Try to keep each socket as vertical as possible Solder the 8 pin IC socket too located on lower left corner ...

Page 12: ...p DI Assembly Guide 3 5 Solder the 3 PDIP Relays Take note of the Relay part number that came with your kit and follow the next step IMPORTANT Insert Relays in proper orientation Match the white band on PCB silkscreen with the Relay s line markings ...

Page 13: ...wn and secure 7812 metal tab with machine screw and nut If your kit came with A18W K Relays Do NOT install the 7812 Voltage Regulator Instead solder a JUMPER wire across pin 1 and pin 3 of IC4 location Note Photos on this guide show A18W K relays with a 7812 Regulator also installed This combination will also work but the 7812 Regulator is not really necessary in this case ...

Page 15: ...Electrolytic Capacitors These capacitors have polarity markings one lead is and the other lead is IMPORTANT Observe the proper polarity when inserting these capacitors Match polarity with PCB silkscreen markings All negative leads of electrolytic capacitors are orientated facing downwards ...

Page 16: ...Copyright 2016 FiveFish Audio NK 72DI Mic Preamp DI Assembly Guide 3 8 Solder Q1 Transistor IMPORTANT Observe proper orientation and the direction transistor is facing Follow the PCB silkscreen markings ...

Page 17: ... But for consistency use the same color arrangement on all mic preamp kits you ll build A typical color arrangement may be GREEN for phantom power switch BLUE for 20dB Pad YELLOW for polarity reverse RED for Mic Instrument selector switch IMPORTANT The LONG LEG of the LED must be oriented at the TOP position as shown for the NK 72DI Mic Preamp Kit NOTE LEDs are installed from the bottom Bend LED l...

Page 18: ...led You can use anywhere from a 1 16 hole up to 1 8 hole size The larger the drill size you use the less critical the alignment of the LED to the hole Green LED Blue LED Yellow LED Red LED NOTE The LEDs are mounted at the bottom of the PCB Smaller sized holes look better as LEDs are not too overpowering bright when lit up However exact alignment is more critical You may need to enlarge the hole on...

Page 19: ...ey re mounted horizontally level and not crooked or mis aligned TIP You can use masking tape to hold the switch securely in it s place while you solder them Solder one leg terminal of the switch first and re check if the switch is still horizontally level If everything looks good solder the rest of the switch terminals ...

Page 20: ...Copyright 2016 FiveFish Audio NK 72DI Mic Preamp DI Assembly Guide 3 12 Solder all medium sized 220uf electrolytic capacitors IMPORTANT Observe proper polarity and orientation of and leads ...

Page 21: ...o NK 72DI Mic Preamp DI Assembly Guide 3 13 Solder the 1 4 TRS Instrument Jack Make sure to mount TRS jack level and flat as possible with the PCB You may need to push the TRS jack down to be flat as possible then solder the legs ...

Page 22: ... PCB Adapter with right angle headers to secure the Input Transformer to the main board and make electrical connection 3 14 1 Solder the Right Angle headers to the PCB Adapter with the Right Angle headers mounted at the Bottom Side 3 14 2 The PCB Adapter has silkscreen on the Top side with the Pad Pins numbered Align these numbered Pads with the corresponding Transformer Pins Solder Transformer pi...

Page 23: ... Secure the Right Angle bracket to the PCB using the 1 4 machine screw and 4 40 nut DO NOT TIGHTEN THE SCREWS YET 3 14 4 Solder the headers to the main board Make sure the PCB adapter board is flushed to the main board and not tilted up or skewed After successfully soldering the headers you may now re adjust the Right Angle Bracket and tighten the screws 3 15 Mount the Input Transformer ...

Page 24: ...mer to the PCB Use the 4 long machine screws with 4 lock washers on top of the transformer and 4 lock washers between the transformer and PCB Use the 4 lock nuts to secure the transformer to the PCB IMPORTANT Solder the different colored transformer wires to their corresponding locations on the PCB ...

Page 25: ...016 FiveFish Audio NK 72DI Mic Preamp DI Assembly Guide 3 17 Install mounting spacers to PCB using the Aluminum Male Female Hex Spacers and 4 40 nuts Then mount PCB to aluminum sled using the provided small screws ...

Page 26: ...Currently the VU Meter kit cannot be used with the Acrylic Front Panel unless you drill 5 additional 1 8 holes for the LEDs The Anodized Aluminum Front Panel upgrade will have the ready made holes for the VU Meter LEDs If there is enough requests for VU Meters for use with the Acrylic Front Panel we will create an alternate Acrylic Front Panel design with the VU Meter LED holes So let us know what...

Page 27: ...2016 FiveFish Audio NK 72DI Mic Preamp DI Assembly Guide 3 19 Solder the 10K Potentiometer as shown below Use a couple short pieces of wire to connect potentiometer to the board Connect these 2 terminals together ...

Page 28: ...acrylic front panel Tighten nuts of potentiometer and 1 4 TRS jack Then install knobs IMPORTANT Do not overtighten nuts to avoid damaging the Acrylic Front Panel NOTE Anodized 0 125 thick aluminum CNC engraved Front Panels are also available as an upgrade option Contact FiveFish Audio for details ...

Page 29: ...NOTE NK 72DI Mic Preamp Kit comes with a 3mm Transparent Gray Acrylic front panel The lighted LEDs show through very nicely through the tinted transparent front panel 48V Phantom Power 20dB Pad Polarity Reverse Mic Instrument DI Select 1 4 Instrument Input Gain Control ...

Page 31: ...DI Mic Preamp DI Assembly Guide 4 ERRATA MANUAL CHANGE INFORMATION 4 1 Correction R2 located nearest the Input Transformer header pins new value is 4K7 ohms 4 2 Correction RLIM located inside Discrete OpAmp outline new value is 25R5 ohms ...

Page 32: ...solder joints or short circuit bridges 5 2 Check if all diodes are installed in correct orientation 5 3 Check if all polarized electrolytic capacitors are installed in correct orientation 5 4 Check if all relays are installed in correct orientation 5 5 Check if jumper to bypass IC4 is required only required if using A18W K Relays 5 6 Check if Discrete OpAmp is installed and secure in it s socket 5...

Page 33: ...used the optional Selector Switch upgrade But removing any DC at this point will also help the potentiometer and avoid any pops down the road when the potentiometer gets dirty or it s tracks worn out To perform this adjustment step power must be applied to the module See section 11 for pinouts on where to apply the V and V voltages and ground connection This step obviously needs a dual power suppl...

Page 34: ...Copyright 2016 FiveFish Audio NK 72DI Mic Preamp DI Assembly Guide Connect Positive Red lead of multimeter to OUT pin on OpAmp Connect Negative Black lead of multimeter to GND of module ...

Page 36: ... 1000pf 50V C5 C12 0 NOT USED C6 C7 C15 3 47uf 50V C10 1 10uf 50V NON POLAR C11 1 470pf 50V C18 C19 C24 C25 4 220uf 50V C21 C22 CF CLS 4 100pf 50V SEMICONDUCTORS D1 D2 D3 D4 4 1N4148 LED1 LED2 LED3 LED4 4 GREEN BLUE YELLOW RED Q1 0 NOT USED Q2 1 BC546B NPN transistor IC1 DISCRETE OPAMP 0 DOA 17 DISCRETE OPAMP IC1 DISCRETE OPAMP 0 DOA 12 DISCRETE OPAMP IC1 DISCRETE OPAMP 0 HYBRID DOA IC2 1 OPA2134P...

Page 38: ...TOR LOCK WASHER 1 FOR 7812 REGULATOR 4 40 NUT 1 FOR 7812 REGULATOR L BRACKET 1 FOR INPUT TRAFO LOCK NUT 1 FOR INPUT TRAFO 4 40 X 1 4 BOLT 1 FOR INPUT TRAFO 10P RIGHT ANGLE HEADERS 1 FOR INPUT TRAFO INPUT TRANSFORMER PCB ADAPTER BOARD 1 FOR INPUT TRAFO LONG MACHINE BOLTS 4 FOR OUTPUT TRAFO LOCK NUT 4 FOR OUTPUT TRAFO LOCK WASHER 8 FOR OUTPUT TRAFO PANEL BLACK KNOB 1 KNOB FRONT PANEL ACRYLIC 1 FRONT...

Page 43: ...ackwards Please review Step 3 19 and look closely at how the wires are connected to the potentiometer You need to swap the location of your 2 wires if your gain is backwards I hear a popping sound when I switch from DI Instrument to Mic Input I m using a Condenser microphone with 48Volt phantom power switched ON Turn OFF 48V Phantom Power switch and wait a few seconds before switching between DI I...

Page 44: ... FiveFish PSU 2448 Power Supply Kit and Power Transformer to supply regulated voltage and 48V phantom power to your NK 72DI module You may also mount the NK 72DI Mic Preamp inside a custom 1u 19 rack case Just supply the NK 72DI module with the neces sary voltages and connect to XLR male and female jacks Use the wiring guide below You can use a 15 pin EDAC connector or solder the connection wires ...

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