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Assembling the Nutclough Amplifier Kit

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An assembly guide for the Open Source Hardware Camp 2014 kit.

The Nutclough is a simple mono audio amplifier that can be used with an iPod, mobile phone or similar audio device which has a 3.5mm jack socket output (or other devices with the correct cable). The kit was created by Calrec Audio for use in workshops and as part of their 50th anniversary celebrations. Calrec designed the amplifier circuit and commissioned Boldport to use PCBmodE to turn it into a beautiful, but functional PCB design.

If you receive a kit at OSHCamp 2014 and you are new to electronics, don’t worry because there are some helpful notes later on.

Kit contents

Inside the larger bag can be found the following:

  • Speaker

  • 9v Battery

  • PP3 Battery clip

There is also a smaller bag with the following electronic components:

  • PCB

  • 2 x Jack sockets

  • potentiometer

  • TBA820M IC

  • PP3 Battery Terminal

  • 2 x 16v 220uf capacitor

  • 3 x 16v 47uf capacitor

  • 3 x polyester capacitor

  • ceramic/tantalum capacitor

  • 2 x 4.7k ohm resistor

  • 330 ohm resistor

  • 27k ohm resistor

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And a second smaller bag which contains the following mechanical components:

  • 2 x M2.5x4 screws

  • 2 x M2.5 nuts

  • 4 x M3x35 nylon stand-off

  • 8 x M3x12 nylon screws

  • knob

  • steel key ring

The full bill of materials and schematic can be found on Solderpad.

Notes for novices

The only thing which may be slightly confusing is identifying the value of each resistor. There are lots of useful guides on how to do this on the web. However, here is a list to make it a bit easier.

Value              Colour code                                  Placement

330 ohms         Orange, Orange, Brown, Gold            R1

1 ohm             Brown, Black, Black, Silver, Brown      R2

27k ohms         Red, Violet, Black, Red, Brown           R3

2 x 4k7 ohms    Yellow, Violet, Red, Gold R4 and         R5

56 ohms           Green, Blue, Black, Gold, Brown         R6

470 ohms         Yellow, Blue, Brown, Gold                  R7

The other components are all easy to identify using the markings on the PCB and the bill of materials on Solderpad. You just need to be careful to ensure that the electrolytic capacitors (round metal cans), IC and LED are all inserted the correct way around.

First things first

Start by soldering all the components from the 'electronics bits' bag onto the PCB (word to the wise, its much easier to solder the smallest on first!) I also found it helped to secure the components in place with blu tack before flipping the PCB to solder held them in place.

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Optional extras

There is an optional LED to indicate when the amplifier is powered, which is currently not shown in the schematic. This must be used in conjunction with a 470 ohm current limiting resistor, which is inserted into position R7 and the LED is inserted into D1.

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Battery and speaker wiring

Attach the PP3 battery clip to the underside of the PCB and secure it with the M2.5 screws and nuts.

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Insert the battery into the battery clip and hold the terminal clip against it to give you an indication of how much wire will need trimming before connecting to B1 on the PCB. When doing be careful not to let the bare ends of the wires touch so that the battery shorts out.

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The remainder of the snipped wires should then be used to connect the speaker to LS1 on the PCB. Once soldered in place be careful not to move the wires around too much as they are quite thin and cannot tolerate much strain before they will break.

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Testing time!

Make sure that the battery terminal is attached and if you then switch the power switch the LED should illuminate.

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Next use the supplied cable to connect a phone, iPod or MP3 player which has a 3.5mm jack socket, with the other end connecting into J1on the amplifier (this is the amplifier input, J2 is an output for use with an external speaker).

Start playing some music!

Note that the part of the PCB with the illustration of Calrec Audio’s HQ, Nutclough Mill, can be snapped out and used with the supplied keyring.

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Trainee Electronics Engineer, currently studying towards my degree in Electronic Engineering at the University of Hudderfsield. Completed my HND in Electrical & Electronic Engineering from Bradford College 2017. Love to try new things and build interesting projects!

14 Aug 2014, 6:45