Our Repair Service
Headset Services Limited have an ISO9001:2008 and EASA Part145 approved workshop where repairs, servicing and modifications are carried out on site. The workshop can also custom build leads, converters and adapters to suit customer's needs. Spare parts are stocked for all major brands. We have many years of valuable experience and equipment is repaired to the original manufacturer's specifications.
HSL has the ability to repair all types of aviation headset such as Bose, David Clark (exception of X11), Sennheiser, Plantronics, Peltor, Telex, Clement Clarke and handsets (Holmco, Becker, Boeing, Airbus, Telex, Telephonics and Electro Voice). HSL is also able to service, repair, modify and refurbish pilot helmets and Search and Rescue radio equipment.
Alpha Helmet Servicing
HSL is authorized to service, modify and repair Alpha Helmets. You can arrange your helmet by following the steps below.
Fill in Repair Form
Print Page (this includes the address label for Headset Services Repair Centre
Await collection or send helmet(s) in Receive quotation for all work required
Confirm we should proceed
Helmets returned to you (Typically 5 - 7 working days)
If you require a collection, please telephone 01273 234181.
Warranty Headset Repair Centre
HSL is authorized to carry out warranty repairs on equipment manufactured David Clark, Bose and HISL (Alpha Helmets) We offer a quick turnaround for repairs - usually within 1 - 2 weeks subject to parts availability. We have also recently introduced the option of an express service which reduces the turnaround time to 1-2 days (again subject to parts availability). Please ask for details and prices.
X11 Headset Repairs
HSL is no longer able to repair or service the David Clark X11 headset. If you need to have your X11 repaired, please send it directly to David Clark in the States.
Lightspeed Headset Repairs
HSL is no longer able to repair or service the Lightspeed headset.
Please complete and send with item
Before sending in your repair item, please download the Repair
Form and complete all boxes. Please remember to clearly state what is
wrong with the item and to include a daytime telephone number, so that
one of our technical engineers can contact you.
Please include the completed Repair Form with the item when sending into our repair centre.
By downloading and completing this Repair Form you are agreeing to our Terms and Conditions.
Frequently Asked Technical Questions
Will my headset work with another headset of a different type? Possibly - the only way to guarantee compatibility is to use headsets that are exactly the same type. Different headset types (as long as they are of the correct specification for the comms system) may work together; but this is dependent on the intercom / radio system fitted to the aircraft and how it has been installed in the aircraft. Different headsets may work well together in one club aircraft: but not in another.
Why is my headset earphones now only working on one side? Many modern headsets now have Stereo capability but not many aircraft do. There is usually a small slider switch on the plug splitter box that switches from mono to stereo. If the switch is set to stereo and the headset used in a standard mono aircraft - only one earphone will work. So check the switch.
What are the different plug types that are used on aviation headsets? Twin Plugs - the Mic plug is thinner than the Phono plug. These are commonly used on most general aviation aircraft as well as most Airliners. UK NATO plug is a short brass plug with 4 contact rings commonly used on all UK Military aircraft and some helicopters. (Often denotes military spec headset that is not useable on GA Aircraft) USA NATO plug (U174/U) Similar to the UK NATO plug but has a silver nickel finish to contacts and a smaller body diameter. Used on many helicopters and ground crew headsets * Note. The U174/U plugs on the ground crew headsets are wired differently to standard aircraft U174/U plugs! 5 pin XLR plugs are nickel or black bodied metal plugs with 5 small pins arranged in a semi-circle. Most commonly used on the Airbus range of Airliners.
What's the difference between Civil specification headsets and Military types? There are 3 main types of headset impedance specifications - none are interchangeable with each other without specific adapters / converters etc. (available from Headset Services Ltd) The USA Mil headset is difficult to convert to civil spec, the NATO headset can be converted to civil spec with an adapter box. You cannot economically convert civil spec headsets to military spec. Even after conversion you may still encounter compatibility problems 1.Civil Specification headset - 600ohm total earphone impedance. Microphone is "100 ohm carbon level" which is achieved in a variety of ways - old style carbon mic. Amplified dynamic mic or amplified electret mic - as per David Clark headsets. 1.75m straight cable with twin plugs. 2.NATO spec Military headset - 150 ohm total earphone impedance. Microphone is a 150-ohm dynamic microphone. UK NATO plug. 3.USA Military Specification - 9.5-ohm total earphone impedance. Microphone is a 5-ohm dynamic microphone. USA U174/U NATO plug.
How do I calculate earphone total impedance? Earphone impedance calculations; you can wire the earphones in series or parallel. Wiring earphones in series doubles the total impedance of the earphones i.e. 300 ohm earphones in series = 600 ohm total impedance. Wiring earphones in parallel halves the total impedance of the earphones i.e. 300 ohm earphones in series = 150 ohm total impedance.
What Microphone types are available? There are a variety of different microphone designs…
"Dynamic" microphones are essentially a loud speaker in reverse - you speak into a small cone / membrane which has a coil attached to it that moves in the magnetic field of a permanent magnet in the element. The cone moves in time with the voice input and the coil moving in the magnetic field has a variable signal induced into it by the magnetic field of the magnet. This varying signal becomes the mic output signal / voltage from the microphone.
"EM or Electromagnetic mics" - are similar to a Dynamic mic but use a rocking armature system for the coil / magnetic assembly.
"Carbon" mics are made by enclosing carbon granules within a flat capsule. A small voltage is applied to the element. When a voice input moves the capsule diaphragm, compressing the granules the effect is to vary the voltage signal through the element. This becomes the mic output signal.
Electret Mic elements are a modern design based on capacitance. A charged plate has a voice diaphragm in front of it - as the voice moves the diaphragm in the field of the plate, it changes the capacitance - this variance is picked up by a 'FET' amp, which is connected behind the plate. A small voltage is supplied to the FET amp for it to work and to output a signal as the mic output.
Dynamic and EM mics do not require a voltage feed to them to work - they output their own voltage signal. Carbon and Electret mics need a supply voltage from the main equipment to enable them to work. This is why the different mic types are not interchangeable.
Dynamic, EM and Electret mics have a small output signal level, whilst Carbon mics have a much larger output signal.
Microphones used in aviation - Military microphones tend to be Dynamic types.
Civil spec microphones were historically based on the Carbon Mic element. But as dynamic and Electret mics have a much nicer signal output in terms of noise cancelling and audibility, modern microphone development has lead to the development of amplified Electret and amplified Dynamic mics that mimic the old carbon mic output levels to match the requirements of the Civil spec avionics.
Virtually all modern aviation headsets use amplified Electret mics (to carbon level) but are often incorrectly described as just "Electret mic". Eg: David Clark H10-13.4. There are also some amplified Dynamic headsets eg: David Clark H10-30 and some Peltor headsets.
Civil spec microphones tend to have the amplifier built into the mic element (like the David Clark M4 or M7 mics) or some headsets have the amplifier in the headset's ear shell (like most Peltors).
Are they interchangeability? As a general rule you can amplify a Military spec microphone to civil spec carbon level, with the use of a suitable amplifier in line. This is usually a plug in box in the downlead of the headset. These are commonly used by Warbird owners using military helmets etc in an aircraft fitted with modern radios - these are available from Headset Services Ltd.
Civil spec mics cannot be used in a military system without an electronic interface box and separate battery power supply to power the mic element. These are not commonly available or used but could be "custom made" by Headset Services Ltd if required.
Microphones used in other equipment? Most modern communications equipment tends to use the Electret mic element (unamplified) as the microphone of choice. They are small, lightweight, cheap and offer good noise cancelling audibility. Eg: PCs, PMR Radios and Mobile Phones.
Aviation headsets with their high output carbon mics are not always suitable for non-aviation applications without some interface matching. Conversely, headsets for non-aviation uses cannot be used in aircraft applications without amplifiers in line.
The MEL Group
MEL Aviation Ltd acts
as the group's headquarters.
T: +44(0)1787 373282
F: +44(0)1787 310812
A: Laurence Walter House,
Addison Road, Sudbury,
Suffolk, CO10 2YW.