For the longest time, ASTi has been sending engineers on-site to sort out occasional reports of problems with customer installations. In almost every case, we have found that a major contributor—if not the root cause of the problems—has been some cabling issue.

Not to say that there haven't ever been other model configuration issues, but over the past ten years, there has been a steady drumbeat message saying that most of the installations have shown dramatic improvement after we made changes in the audio cabling. At some sites, we managed to make the problems disappear entirely; at others, we have improved the audio to some level above basic intelligibility.

There are many—too many—installations where we pointed to the customer's military headsets or long cable runs and said ruefully that this was the best we can do. Well, it appears that in many cases, it wasn't!

To resolve cable installation problems, we have always applied accepted, good audio engineering practices to our cable design recommendations: good-quality, twisted-pair shielded cable, best grounding practice, etc. This has certainly been very effective in mitigating some of the worst problems.

But finally, about six months ago, we decided that we should conduct an in-depth, objective investigation into the problems encountered with different types of headsets and audio cable combinations. We aimed to figure out the characteristics of any potential audio problems, what works (and what doesn't) so we could make definitive headset and cabling recommendations to our customers.

*Geek-Speak Noise & Crosstalk: voice frequency coupling, generally inductive, between signal lines

The bottom line is: Many commonly-used cable techniques are not effective in eliminating noise and crosstalk*. In fact, some of the biggest problems with headsets are not the headsets themselves, but the cables used by the manufacturers.

Obviously, the higher the current drawn by a headset, the more prone it is to cross-coupling. But even so, the performance of the worst offending headsets can be substantially improved by changes in the cabling. The difference in crosstalk performance between good and bad installations can routinely be over 40 dB! Good audio cables can make your setup sound over 100 times better than bad cables.

One thing we were surprised to discover: There is no published data or information on the specific configuration of audio cabling that is routine in simulator communication system installations. Therefore, it is unlikely that you will find anything approaching the same level of understanding or expertise anywhere outside of the ASTi engineering team.

Well firstly, if you are ordering a new system please let ASTi supply the cables. If you can't do that, then at least let us review your cable designs and product selections. We may have some valuable suggestions.

We also offer a very reasonably-priced headset/peripheral evaluation service that will allow you to receive a full and comprehensive written report on any and all audio components that you are considering using in your trainer installation.

Well, you should talk to us.

Our tests show that in some cases, as little as 2' of poor cable quality can contribute over 40 dB of crosstalk!

We can quite possibly devise some simple tests between a couple of positions using new ASTi-supplied cables and see (hear) whether new cabling is truly the answer. And even if complete replacement of the cabling is out of the question, it is conceivable that by addressing some of the worst contributing elements, the situation can be much improved.

The graph above shows the vast disparity in noise and crosstalk performance between different types of cables. Measurements were taken using the same widely-used, military style headset with each audio cable.

As you can see, improperly wired audio cables—even if they're of good quality—can have profoundly adverse effects on audio performance (45.95 dB). Unfortunately, the most commonly-used type of audio cable also suffers from performance anxiety (43.44 dB).

While, at the other end of the spectrum, properly wired cables can make a world of difference (6.02 dB), but can be up to 10 times more expensive than ASTi-recommended cabling, which performs slightly better at 4.44 dB above the hardware's noise floor.