In the second of PCN's new Workbench series, Kenn Garroch shows you how to provide the BBC Micro with a better speaker - and a few other improvements as well

The quality of sound from the BBC Micro has much room for improvement. For instance, the internal speaker is too small. Getting around this drawback is pretty straightforward; as the micro's speaker plugs into the main circuit board at PL15, a replacement can also be plugged in at this point, as long as it matches the 8ohm impedance.

While we're at it, a few other features can also be added: a plug in system that means no modifications to the BBC itself; and a socket arrangement that allows the internal speaker to be available when the external one is not.

The first step is to take the Vero boad and solder the Minicon socket onto it. Next, cut the two metres of cable into three pieces 40cm, 20cm and 140cm long. Two of the Minicon terminals should be clamped and then soldered to each of the wires at one end of the medium-sized cable after baring and tinning it. The other end of this wire is bared and soldered onto the 0.25in jack socket.

Of the two pairs of connectors on this socket, the pair with the spring levers should be attached to this wire. The other pair is attached to the two wires at the end of the smallest length of cable. The other end of this cable is attacked to the Vero board in holes adjacent to the Minicon socket, on the same strips.

The largest length of cable is attached at one end to the speaker, and at the other end to the 0.25in jack plug. The best way of doing this is to place the plug in a vice before you attempt to solder it, or you may singe your fingers. All the hard word is now over.

On the right-hand side of the back of the micro are two holds: one for the Econet connection, the other for a reset switch. The 0.25in jack socket should be placed in the reset switch hole. Many later versions of the BBC Micro have this hole covered by the thin black plastic on the back of the machine. Just use a small, sharp knife to reveal the hole.

Stich the Vero board to the inside of the case next to the power supply with double-sided tape. Push the internal speaker plug onto the Minicon socket, reassemble the micro and turn it on. If you don't hear the boot-up beep, turn everything off and check the connections. If all is well, plug the external speaker into the socket at the back and hit CTRL-G. Again, you should hear a beep, but much better than before.

If you want to alter the volume, the small preset potentiometer next to PL15 can be adjusted with a small screwdriver. It's pretty easy to remove the keyboard to do this. A further way to improve the sound is to build a box for the speaker.

 
Total cost £4.41