FiveFish Studios NK-72DI Bedienungsanleitung
FiveFish
Studios
NK-72DI Mic Preamp + DI Kit
Assembly Guide
Copyright © 2016 FiveFish Audio
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 Audio. This document is solely provided
to the kit builder of the NK-72DI Mic Preamp.
Copyright © 2016 FiveFish Audio
veshaudio.com
Assembly Guide Revision 1.1 - 20160530
Dear Customer,
ank you for purchasing our NK-72DI Mic Preamp + DI Kit.
Great care has been taken to make this assembly guide complete and as accurate as possible.
Our goal is to make your assembly work easy and trouble-free, and deliver to you a working,
reliable, and high-performance mic preamplier.
is 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.veshaudio.com, or via our facebook page.
Sincerely,
FiveFish Team
FiveFish
Studios
FiveFish Audio www.veshaudio.com
Copyright © 2016 FiveFish AudioNK-72DI Mic Preamp + DI Assembly Guide
GENERAL
This assembly guide must be reviewed for familiarization
with safety markings and instructions before assembly of
the Mic Preamp kit.
BEFORE APPLYING POWER
Verify that all components and parts are inserted in the
right location and correct orientation. Visually inspect
that there are no cold solder joints, or short-circuits.
The WARNING sign denotes a hazard. Pay attention
to the procedure, instructions, or the like, which if not
correctly performed could result in damage to your
equipment, electronic component or personal injury.
SAFETY CONSIDERATIONS
Any interruption or disconnection, or lack of connection of
the protective earth terminal/safety ground may cause a
potential electric shock hazard that could result in personal
injury. (Grounding one conductor of a two conductor outlet
is not sufcient 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 rst-time you power your mic preamp project. If
you made any mistake during assembly of this kit (for
example: components inserted in wrong location, wrong
orientation, short-circuit in your soldering job, etc.) you will
not be subjecting the built-in power supply of your rack
to the problem, and avoid damaging your power supply.
If you don’t have a lab power supply and instead will be
using your rack to power directly this project the rst time,
I recommend using an extender card with built-in fuses
to protect your rack power supply from accidental shorts
or over-current. (The in-line fuses will blow if there is
overcurrent or short-circuit condition, thus protecting the
rack power supply).
Copyright © 2016 FiveFish AudioNK-72DI Mic Preamp + DI Assembly Guide
GENERAL INFORMATION
1. DESCRIPTION
The NK-72DI is a high-performance, low-noise Mic Preamp and Direct Inject (DI) combo unit for use with API 500 Series lunchboxes
or racks. It is a transformer-based preamp design, using Carnhill/UK Input and Output Transformers to deliver a rich, big sound.
The NK-72DI design utilizes a Discrete OpAmp for signal amplication and direct drive of the output transformer. The amount of
voltage gain or amplication is set by a simple resistor, which can either be a single-turn potentiometer or a 12-step selector switch
with the necessary resistor ladder values. The stock NK-72DI Mic Preamp Kit is supplied with the single-turn potentiometer but
can be upgraded to use a 12-step selector switch. There is also built-in RFI input and output protection, to protect the preamp from
radio frequency interference.
The 48Volt section utilizes a soft-start design, such that 48Volts is applied gradually to your expensive 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 features a built-in DI input for use with high-impedance instruments like electric guitars, bass guitars, etc. A
push-button switch is used to select either Mic-level or DI-input to the unit. A 1/4” TRS jack is provided on the front panel for
instrument input.
The NK-72DI Mic Preamp Kit can be upgraded with a 5-LED VU Meter board and Stepped-Gain Selector Switch. These extra
options are not necessary for the preamp’s operation, but is provided as a “nice-to-have” upgrade step. The Stepped-Gain Selector
Switch and 5-LED VU Meter kit are a separate purchase and not part of the basic NK-72DI kit package.
The NK-72DI requires a dual power supply, and +48Volts (power supplied by a 500 series rack). When using our DOA-12 Discrete
OpAmp, and racked separately, it can be powered up to (+/-22 Volts) for more headroom before clipping.
Copyright © 2016 FiveFish AudioNK-72DI Mic Preamp + DI Assembly Guide
2. TOOLS & EQUIPMENT REQUIRED
A few basic tools and equipment are required to assemble this kit. These basic tools are not supplied with the kit.
2.1. Soldering Iron and Lead - We recommend a temperature-controlled soldering iron. DO NOT USE A BIG 100 WATT
SOLDERING GUN. A small 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. Magnier & Lamp - I recommend a clean and well-lighted space for your assembly area.
2.6. Other Tools (not required, but nice to have) - Component lead bender, vise, tweezers, wire stripper.
Copyright © 2016 FiveFish AudioNK-72DI Mic Preamp + DI Assembly Guide
3. ASSEMBLY GUIDE
BEFORE YOU BEGIN: Pick a clean work area where you can leave your work-in-progress unattended if you need to.
Keep individual components in their labeled zip bag until you’re ready to solder them. Kit components have been sorted and
labeled for your convenience. 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 rst. Then solder the taller and larger components next.
Big bulkier components like switches, jacks, big capacitors and transformers are best soldered last.
Please review Section 4.0 for any
ERRATA and last minute changes
before starting assembly.
Copyright © 2016 FiveFish AudioNK-72DI Mic Preamp + DI Assembly Guide
3.1 Solder all 1/4 watt Resistors.
Copyright © 2016 FiveFish AudioNK-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.
Copyright © 2016 FiveFish AudioNK-72DI Mic Preamp + DI Assembly Guide
3.3 Solder all Ceramic capacitors.
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