Assembling the Nutclough Amplifier Kit
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.
Inside the larger bag can be found the following:
PP3 Battery clip
There is also a smaller bag with the following electronic components:
2 x Jack sockets
PP3 Battery Terminal
2 x 16v 220uf capacitor
3 x 16v 47uf capacitor
3 x polyester capacitor
2 x 4.7k ohm resistor
330 ohm resistor
27k ohm resistor
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
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.
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.
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.
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.
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.
Make sure that the battery terminal is attached and if you then switch the power switch the LED should illuminate.
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.