Decoding these extra sounds and delivering them to your surround system has often been a case of “choose your poison”, with none of the specialised equipment for decoding one system being able to reproduce another's with any great results.

Enter; the 'Surround Master' from Involve Audio. This little piece of kit claims to be able to decode pretty much any type of stereo-encoded surround sound, into 2.0, 4.0, 4.1, 5.0 or 5.1 discrete channels of surround sound audio. How can you decode stereo into 2 channels of surround sound? That’s what I asked myself. Time to hook this thing up and give it a try.

In the box you get the Surround Master unit, a brief instruction manual, a 9V DC multi-plug power adapter, and enough RCA cables to connect the unit from a 2-channel input to 5.1 channel output. The unit itself is a simple black plastic case with raised “chrome” lettering; rather light weight. I needed to know more before undertaking this review, and being sceptical in it's ability to convey good sound, other reviews online told me otherwise. Not being someone easily swayed by others’ opinions, I had get this thing going to test all the different claims from the makers.

Connection to my vintage Pioneer VSX-AX1 surround amplifier was quite simple using the 5.1 channel discrete inputs, as illustrated in the Surround Master’s instruction book. For the music source, I used my current micro-hifi system – a Sony CMT-SWB300WB, via the headphone output – for USB, WiFi Streaming and DAB+ playback. A Pioneer PD-6500 will serve as the CD player for this test. With the Surround Master switched off in its default pass-through mode, I confirmed the correct connection of all the speakers and set the level from the Sony unit to match the maximum input for the Pioneer CD player and amplifier. Set to 2-channel mode, I held my breath and flicked on the Surround Master’s power switch.”

I was not disappointed. My first impression of the Surround Master was that the expansion of the stereo image was nice – not subtle at all, but not overpowering either. The centre image vocals in Kate Bush's “Army Dreamers” was still rock-solid in the centre of the sound stage. The ambience and incidental vocals seemed to project to the width of the room, and the stage depth suddenly extended an extra metre or so further back into the wall. Interestingly, there was no change in loudness or dynamics, just a bigger sound stage. On closer listening, comparison between the original pass-through and TSS (Two Speaker Surround) mode, there was a slight but noticeable emphasis in the mid-range sounds of the ambient signals compared to the 2-channel original – but not in any immediately unpleasing way. On to the full surround decoding.

In 4-channel mode, I flipped through some older Quadraphonic, Matrix, and CD-4 Stereo encoded recordings of Pink Floyd, Uriah Heep, and Credence Clearwater Revival. The recording quality of the tracks I played varied quite a lot, but generally, the full 4-channel sound was reproduced with the quality of the decoder results varying according to the overall quality of the tracks. One thing I did notice, if the source isn’t almost immaculate in its own quality, the decoder really has trouble discerning the front/rear separation – and in some cases it was just wrong to my ears. On to a Dolby Pro-Logic encoded source ... wow, I was amazed at the clarity and dynamics again – this was an excellent source. The Chesky Records “Gold Stereo and Surround Sound Set-Up disc” – the Left/Right and Front/Rear decoding was almost seamless, and certainly without any noticeable artefacts, wobbling of the surround images, or funny phasing of the bass signals which can be apparent in a poor quality decoder.

At $499.99 RRP, the Involve Audio Surround Master is a must-have for those audiophiles with a broken Sansui or Technics surround amplifier from the 60’s and 70’s, or for someone who wants to know what early surround sound was really like. There’s still a lot of LPs and CDs around with Quad encoding from the original master, and you just won’t get the surround sound from these without the Surround Master decoder.

For more information visit Involve Audio.