Remote Control System
Phil 'DI — Why do I have to endure these terrible puns' Walsh with the second part of his remote control project for amps
Those of you who are really keen will by now have all the relevant amplifiers modified and have a series of stereo cables, long enough to reach a central point at the back of your normal stage set up, terminated with stereo jack plugs. The next job is to build the stage box. This sounds a lot more complicated than it actually is — it is simply a box which gathers in all the stereo cables and links them to a multicore cable. It is possible to do all the wiring directly in the box but a more flexible way would be to use a multicore connector mounted on the box with a corresponding connector on the cable. As I'm into flexibility that's the system I'm going for.
In order to keep things all together, elsewhere on this page is a parts list of all the components you'll need to complete the project. It would be nice to be able to recommend one supplier but in the end I've opted for a combination of suppliers in order to keep the costs down to a minimum. For each component I've quoted the price at the time of writing, a supplier, and an indication of which module the part is used in (S-Stage box; C-Multicore cable; R-Remote box). Details of the suppliers are at the end of the article.
The wiring is all contained in an aluminium box. The instructions that follow assume that the signals coming into the box will be:-
4 PA channels
1 Master PA Volume
1 Echo Send (mono coax)
1 Echo Return (mono coax)
1 monitor amp input (to be used in the talkback circuitry) (mono coax)
1 Bass Amp Volume
1 Lead Amp Volume
1 Rhythm Amp Volume
1 Keyboards Amp Volume
If your rig is slightly different then modify to your heart's content.
Drill 12 holes around three of the sides of the box, of a suitable size to take the 12 cables with grommets. In the remaining side cut a hole for the 37 way plug according to Fig 1.
Having bolted the plug to the case solder the nine stereo leads to the plug contacts according to the wiring scheme in Fig 2. The three mono coax leads can also be wired in. Two points to note:-
1. If you did the conductivity test on the C tags of the pots that I suggested last month, then you can common all the appropriate C wires onto one pin of the plug, leaving extra pins for expansion at a later date.
2. If the PA (or any other) amp has an internal reverb you can make up a jack plug lead and connect it to two of the spare plug pins. Add a switch to connect the two pins together on the remote console and you have remote reverb switching.
Drill appropriate holes in the top face of the console for the controls you have. A suggested layout is shown in Fig 3. Before fitting any components to the panel, use Letraset to label the pots, sockets and switches (remember the knobs will take up a bit of space so allow for them) and then seal the surface with an aerosol spray sealer.
Fit the pots, switches and sockets to the panel and then cut a hole for the 37 way connector in the rearside of the console. Using stereo or mono coax as appropriate connect the pots to the multi-connector socket using the same schemes as before, ie the PA master volume pins in the stage box should mate with the PA master volume sockets in the remote console. The effects on/off switch is wired across the two finger contacts on the effects on/off socket. Similarly the microphone talk button is wired across the microphone socket. The echo send, return and on/off are all ¼" mono sockets.
It should be possible at this stage (excuse the pun) to test it all out because you can now plug the Stage Box and Remote Console together without the benefit of the multicore cable. The microphone used should be low impedance (as should be the amp input) as you will lose a lot of signal down the cable when you fit it. High impedance will work but it will be a bit noisy.
If you've done the wiring correctly then everything should check out OK. If not, carefully check the wiring on the 37 way plug and socket to make sure the correct pins are connected to the correct sockets! Those of you who used a common 'C' connection may find that you get a lot of hum if you commoned more than one amplifier. This is due to a hum loop, as beloved of Hi-Fi enthusiasts. The simple answer is to disconnect, at the mains plugs, the earths of all but one of the amplifiers. It is also worth checking that any outboard effects used are not mains earthed — they should get their earthing from the PA amp via the effects send/return wiring.
This is the most tedious part of the job. It is simply a matter of soldering the correct wire to the correct solder tags. It is worth starting with just the three PA master volume wires just to checkout that you have got it right. It really doesn't matter which wire you use for what EXCEPT that the master PA 'C' connection should be connected to the screening braid of the multicore.
Rapid Electronics Ltd (Contact Details)
Rapid accept telephone orders with Access or Visa cards (minimum order £5). Their catalogue is available by phoning the above number.
This firm only deals with the trade. The only way you can deal with them is to get a local TV repairer who has an account to place the order for you. It's up to you to haggle about how much he is going to charge you for this service.
|No.||Order code||Part||Cost Each ex. VAT||Supplier||Module|
|2||15-0115||37 way plug||£1.00||Rapid||C,S|
|4||20-0145||mono jack skt||£0.20||Rapid||R|
|3||20-D110||mono jack plug||£0.17||Rapid||R|
|9||32-0145/50/||knob col. cap||£0.16||Rapid||R|
Feature by Phil Walsh
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