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Modifying the subwoofer and speakers



The subwoofer and speakers can be used independently from the wallwasher, but you will need to make some modifications, which usually involves making up some cables or cutting the plugs off. Cutting plugs off, although often the simplest way, should be avoided unless you definitely don’t want to connect the equipment to the wallwasher at some time in the future - if you do, you will have to fit new plugs.

Other speakers can also be used instead of those supplied. There are various options and these are detailed below.


refer to the following tabs / pages for more details:

Pin-outs

Subwoofer and speakers

Wallwasher main unit / Wallwasher circuit description - Sidelights and speakers interface - Speakers section

Wallwasher main unit / Wallwasher circuit diagrams - Sidelight interface circuit - speaker section

Copies of the pin-outs and circuit diagrams can be downloaded from the Downloads page.

Any reference to speakers, unless specifically stated otherwise, refers to the left and right speakerlights or alternative speakers.  



Subwoofer

The subwoofer cannot be used on its own, it must be connected to the wallwasher and the the wallwasher connected to a switched on PC. The reason for this is that the subwoofer has a mains relay inside that switches the mains supply to the subwoofer internal power supply on and off. This relay is controlled via a 5v supply from the wallwasher. This 5v supply is switched on by the CPU inside the wallwasher when:

the wallwasher is switched ON (not in standby).

5v is present at the USB input from the PC (this is not the same 5v that goes to the relay.

Data is present on the USB data line from the PC

These arrangements ensure that when the wallwasher is put into standby or the PC is switched off, the relay opens, thus switching off the mains supply to the subwoofer.


The USB could be connected to a 5v source (such as a USB mobile phone charger etc.) and that will provide the 5v USB input for the CPU. This will allow the wallwasher to be switched ON from standby. However, as the USB is not connected to a PC, there will be not be information on the USB data line and the CPU will not turn on the 5v to the relay.


If you want to use the subwoofer without it being connected to the wallwasher, perhaps because the wallwasher is faulty or you want to use the subwoofer somewhere else, there are two options:

- bypass the relay

- provide a separate 5v supply (PSU) to the relay. This is the best method

Either option means that the subwoofer will NOT be automatically turned off when the PC is turned off and so should be turned off separately.


Bypass the subwoofer relay

This will mean opening up the subwoofer


Disconnect the subwoofer from the mains first

Warning

Because you are altering mains connections, it is important that you take care with what you do. There is a fire / electrocution hazard if work is not carried out correctly. Double check all work before switching the mains supply on.

If you are unsure of what you are doing, get a suitably qualified person to do the modifications for you


There are two ways to bypass the relay:

1) Bridge the Relay Mains in and out connections on the underside of the relay PCB. This is the preferred method as it still retains the protective fuse in the mains circuit. The bridge can be a suitable piece of wire soldered across the terminals as shown. Solid core wire is best as this ensures there are no live loose strands of wire.

DO NOT connect anything to the relay coil side of the PCB. Ensure that there is no connection between the PCB tracks on the mains part of the PCB with the PCB tracks on the relay coil part of the PCB.

Double check the work when finished


Photo


2) Disconnect the Mains in and Mains out plugs from the relay PCB. Cut off the plugs and join the two neutrals together and the two lives together using a suitable enclosed junction box. Looking at the photograph, this means joining the two blue (neutral) wires together and the two brown (live) wires together. These are the UK/Europe colours, other countries may use different colours.

The fuse is no longer in the mains supply and it is important that the mains supply is protected. The mains supply should be protected at source with a 3 Amp fuse. In the UK, this is easily done by fitting a 3A fuse to the plug.

No protection or a higher fuse rating could be a fire risk in the event of an overload within the subwoofer internal power supply



Provide a separate 5v supply to the relay

The supply should be 5v DC. I’m not sure what current is required, but 100mA should be sufficient.

Measure the current used by the relay.

A USB charger suitable?


This is the preferred method because it doesn’t involve any modification to the mains supply and therefore there are no fire or electrocution risks.

The 5v to the relay goes via pins 5 and 6 on the Audio IN (7-pin mini-din) plug. Pin 5 is 0v, pin 6 is +5v. It is important that the polarity is correct because of the diode across the relay coil.


Pins 1 - 4 on the plug connect to the speakers via the wallwasher.

If you are using the speakerlights still connected to the wallwasher, then you will need to make up an adaptor cable as shown in order to be able to connect the plug to the wallwasher and still connect the external 5v PSU to the relay.


Making up the cable

Take a 7-pin mini-din plug and a 7-pin mini-din socket and connect pins 1 - 4 together with a suitable length of cable as shown - about 100mm.  On the socket, connect a wire to pin 6. Connect a wire to pin 5. This is for the external 5v supply connection. A suitable plug should be put on the other end to suit the connection from the supply, or a terminal block could be used.





















Fig. BM1:  Made up cable

The colours shown on the diagram are not necessarily the colours of the wires in the Audio In cable.


Connecting

The plug goes into the Audio In socket on the wallwasher. The plug from the subwoofer goes into the socket. The 5v supply connects to the wires from socket 5 and 6.



A simpler way is to “splice” the Audio In cable that comes from the subwoofer and add the 5v connection to that.


The cable should be cut about 200mm from the 7-pin plug. The distance isn’t important, but you need to make sure that you do not cut it too near the plug or you might not have enough room to work on the cable. You now have two cables:

Audio In, with the plug on that goes to the wallwasher - I’ll call this the wallwasher cable

Cable to the subwoofer - I’ll call this the subwoofer cable.


Trim the outer insulation on both pieces of cable to expose the six wires inside. The four speaker wires need to be joined and the 5v PSU needs to be connected to the the two relay wires on the subwoofer cable - see Fig. BM3.

The two relay wires in the wallwasher cable that are no longer used should either be individually terminated or have their bare ends insulated using insulating tape. Make sure that the two relay wires do not touch each other.


Identifying the relay wires

It is important that the 5v PSU is connected to the relay wires and not the speaker wires, or damage may possibly occur to the amplifier. Below are the colours in the Audio In cable that I have checked, although be aware that colours may be different. If your wire colours are like this, then they are probably used for the same purpose. I have identified the purpose of each wire and the plug pin that it connects to. The Relay 0v wire is different from the rest. It has a dull, slightly greyer surface and has writing on it. If in doubt, confirm what are the two relay wires by doing a continuity test between the end of the wire on the wallwasher cable and the corresponding pin in the plug.


There shouldn’t be any need for screening around the joint, but make sure that there are no short circuits between any of the terminals. An eight way terminal junction box, such as used in burglar alarm circuits could be used for the connections if required.



6
















Fig. BM2:  Audio In cable colours and purpose (colours may vary)

















Fig. BM3:  Spliced Audio In cable with 5v PSU added






Using the subwoofer and speakers without the wallwasher

The amplifier output from the subwoofer is always at full volume. You will need to alter the volume at the source - e.g. on the PC or whatever device you have connected to the subwoofer.

If you want to use the subwoofer with speakers without the wallwasher, you will need to sort the relay out as above.


You can then either connect a different set of speakers (not the speakerlights) or use the speakerlights.


Using different speakers

Split the Audio In cable as above. You will not be needing the piece of cable with the plug on. Instead you can connect suitable speakers (8 Ohm 1 Watt) directly to the terminals as shown below.















Fig. BM4:  Connecting a pair of speakers without using the wallwasher



Using the existing speakerlights

Obviously, the lights will not work, neither will the speakerlight controls, because the speakerlights will only be connected to the subwoofer, not the wallwasher.








Note

The Audio In is a standard 7-pin mini-din plug. It is unlikely you will be able to find one. There are some 7-pin plugs around that are not standard. However, an 8-pin mini-din plug can be used instead and these are easily available. The 8-pin plug does not have the plastic key in the centre. The additional pin on the 8-pin plug is in the centre and when connected to the 7-pin socket, will just go into the key hole.

A 7-pin plug will not fit into an 8-pin socket because the 7-pin plug has the plastic key in the centre. One way to use a 7-pin plug in an 8-pin socket is to remove the centre key from the plug (carefully, so as not to damage the pins). Add this paragraph as a general note on page XXX (general page?) as it’s relevant to a few modifications  / cable extension.

Add somewhere re extending the audio In cable - is this already mentioned somewhere?















Change the name Audio In when referring to the subwoofer, to avoid confusion with the 3.5mm audio in jack
using the subwoofer with a different source - make a note on the general page? and / or the bottom of this page
pulse to ww - see amBX post