Making all the Right Signals


As vehicle manufacturers continue to bury their car stereos deeply into the dashboard and beyond, the professional audio installer has had to find ways of taking the speaker outputs from these and making them suitable to feed into the line-level signal input of an amplifier. For those who have absolutely no idea what I am talking about, here is a brief explanation: Most car stereos send their output directly to the speakers mounted in the car. Quite often, these signals are not good enough to drive a pair of upgraded speakers and therefore, those wishing to radically improve the sound in their cars have to amplify these to a suitable level. However, in many cases these signals are already too high to be fed directly into the line-level inputs of an amplifier and must therefore be attenuated before they are amplified.


There are many ways to attenuate a high-level signal and many of them involve removing part of the signal or simply squashing it to make it fit and in this instance, a little bit like a large person trying to fit into clothing that was built for a much smaller person, some bits are going to be squeezed and misshapen during this exercise. Many of you reading this will already know of Audison BIT and Audio Control products which approach this issue in a very hi-tech manner however, there are much simpler and therefore cheaper ways to get a small distortion-free signal suitable for the inputs of an amplifier. However, as with all things in life, you get what you pay for. FOUR is a distributor of some of the best car audio brands in the business and as such is well-placed to advise customers on how to avoid problems when trying to match a high-level signal to a low-level input. As well as the aforementioned squeezing or distortion of a signal, any device carrying out such a task needs to have some in-built immunity to external interference. This is particularly important in a car which has so many electrical systems on board all of which could potentially inject noise into the signal path.


So, what are the important features to look for? We would always advise people to use an expert for this type of thing but if you are determined and armed with the correct tools and skills then a cursory look at the build quality of the device will tell you a lot. The gauge (thickness) of connecting wires should be sufficient to prevent adding resistance to the signal path which will introduce undesirable distortion. Any pre-fitted connections should be checked to make sure the crimping or soldering has been done correctly. You may not be able to see inside the device but components used should all be of high quality and specific anti-noise measures should have been taken during design and manufacture. FOUR consistently reminds its installers of the need to approach passive signal attenuation using only the very best devices for the job. Italian manufacturer Audison makes two of the finest high quality solutions available under its Connection brand; SLI 2 and SLI 4 which are two-channel and four-channel devices respectively. Each offers a four-fold step down which is adequate for all quality amplifiers and both offer high levels of signal integrity and noise rejection capabilities. These units are housed in purpose designed enclosures and look good enough to keep on show. However, FOUR also carries a range of vehicle specific attenuators or convertors from InCarTec. Many of these are application specific devices and offer plug and play simplicity and are built to a high specification. They are less pretty and really need to be hidden away but they certainly do the job.


Alternatively, you could go online and by a bunch of low grade components sealed in a blob of epoxy resin with bell wire coming out of it. This would save you money in the same way that a Donkey is far cheaper than a racehorse. However, it may not do as well in the Grand National!

If you have any doubt as to your ability to select a component that will work in your application, we would always advise a visit to your local FOUR MASTER where the true experts ply their trade!

four masters gold sm

Call 0800 652 5125 or visit to find your nearest expert.

(Content supplied by Driving Sounds –