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The results from this simple unit can be quite stunning, it really does add a whole new dimension to home entertainment. The effects on some modern films are dramatic! Sky Television are obviously well aware that people use this sort of equipment, since even the trailers on their film channels make very good use of the rear channel.

If your main amplifier has an output available, after the volume control, try connecting the decoder to this, that way the volume of the rear channel will follow adjustments on the main amplifier.

This decoder will only work correctly with Dolby Stereo encoded film soundtracks. The effect of the delay will cause awful results if the unit is used with normal stereo programmes or music.

A Silly Idea!
Here's a further idea that a few of you might like to play around with. If the decoder is used without the front amplifier, on a normal stereo music source, the balance control can be adjusted to give the music in mono with little or no vocals. Do-it-yourself Karioke for those who like that sort of thing! Of course the bandwidth is very limited and the bass beat may be cancelled out as well, but it will probably still sound better than the singing!!

Adding a Power Amplifier
The information in this section is believed to be correct but has not been fully tested. It is therefore offered to more experienced constructors, for further experiment.

Some constructors may wish to incorporate a power amplifier into the same case as this decoder.

As only a few watts of power are generally needed for the rear channel, a suitable amplifier might be the Maplin 8 Watt Power Amplifier kit (LW36P, Price #7.45, Page 292 of the 1992 catalogue). This requires a power supply of about 21V, and a suitable circuit is shown in the catalogue, this could be constructed on a piece of tag strip or Veroboard.

It would be sensible to use the amplifier's power supply to power the decoder circuit. On the Surround Sound Decoder PCB, remove D1 and D2, and replace D1 with a link. The 21V form the amplifier power supply can now be connected to P1 (positive) and P3 (negative). If a different amplifier is used, a supply between 18V and 35V can be used to power the decoder this way.

The audio output from P8 and P9 can be connected directly to the amplifier input, using suitable screened cable. If you get a hum loop, try disconnecting the screen at the amplifier end. It may be necessary to reduce the gain of the power amplifier, by adjusting the values of the appropriate resistors on the amplifier PCB. A suitable connector or terminals for the loudspeaker can be fitted on the rear of the case.

Unless continuous operation at high volume is likely, a metal case should be adequate for heatsinking the amplifier and power supply voltage regulator.