Appeared in DIVER April 2006

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REGULATOR  Apeks XTX50

Later, he sold his company, Apeks, to Aqua Lung and sailed off into a happy and well-deserved retirement.
The rest is history. Post an innocent question on an Internet diving forum today about which of any two regulators is better, and you will be swamped by Apeks-users claiming that to buy any other regulator would be a complete waste of time.
Now you might think that listening to what your potential customers want is rather obvious, but not every companys management thinks this way. Ken may be absent but his spirit is still around at Apeks.
Its latest XTX range of regulators incorporates even more ideas that have been spawned simply by listening to what divers want.
Not sure which mouthpiece you prefer, conventional or Comfobite Have either. The Comfobite puts the load on your incisors rather than your molars.
Do you want a compact second stage or one with a wide exhaust-T that routes exhaled bubbles well away from your face Have either.
Do you want to rig your medium-pressure hose from the right, as is conventional, or from the left as might be more convenient if you are using a regulator on the left-hand post of a twin-set Have either.
Want to make your own choice of mp port from which to run your primary second stage You can. Unique port diameters for primary second stages have been done away with. Want to know more The first stage looks outwardly exactly like the turret-style environmentally dry-sealed diaphragm-style first stage of the TX50 that went before it.
However, it has had the benefit of the gradual refinement that comes only with long production runs.
It is still quite a weighty bit of chromed-brass machining. There are two hp ports and four identically sized mp ports on
a revolving turret. Even the rubber-covered knob on the
A-clamp has been upgraded in its grippiness. The DIN version has an all-metal hand-wheel.
The DST first stage can be used with breathing-gas supplies of up to 300 bar. For those who may be unsure, dry-sealing the first stage keeps the water away from the mechanism, especially important if you are diving in water polluted with detritus that could otherwise get in and interfere with its mechanical action. Some people also think it best to keep the works dry in freezing conditions.
The second stage has been improved, although it is still quite bulky by modern standards. The wider exhaust-T or moustache takes exhaled bubbles well away from the face, and these are no longer as obtrusive as they were with the ATX.
The user can easily swap this wide moustache for the much more compact exhaust-T also supplied with the regulator.

Hard finning
There is the usual knob on the second stage for cranking up the cracking-pressure of the valve. This translates into an ease-of-breathing adjustment.
Also familiar is the large, easily usable switch that can be used to position a vane in the airflow to disrupt the venturi-effect and avoid exponential free-flows near the surface.
For coldwater use, there is the now-familiar heat-exchanger at the junction of second stage and hose, and the positive-to-find purge button is now an oval shape rather than circular.
The Apeks XTX can be used straight from its box with nitrox mixes up to 40% or can be supplied oxygen-clean for mixes up to 100%. Expect the total work of breathing to be in the order of 0.65 joules per litre at ANSTI criteria for depth and pressure.
I took an XTX50 to the Maldives for some 40m-plus dives in strong currents. A little bit of hard finning at those depths tested its ability to deliver sufficient air, but more importantly this air delivery was far more subtle and less directional in the mouth than with earlier Apeks designs.
I think the Apeks designers have raised their game once more to give the competition something else at which to aim. The quantity of air may be the same but the manner in which it is delivered has become more refined.
I enjoyed using the Apeks XTX very much indeed.
The Apeks XTX50 complete with XTX40 octopus-rig costs£449. If you want one rigged with hose to the left, specify that when ordering or take it later to a certified Apeks service technician.
  • Apeks Marine Equipment 01254 692200, www.apeks.co.uk


  • Divernet Divernet
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    + Apeks better than ever


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    - Chromed-brass first stage still a little heavy