I am looking to buy a small portable battery powered amplifier to “boost” the volume in some of my aviation headsets, specifically the David Clark H10-60 and an AVCOMM AC-900 PNR. I have a portable handheld aviation transceiver and a handheld aviation band scanner that I’d like to use with my aviation headsets. Hence the interest in a small “booster” amp for better volume.

AVCOMM AC-900 PNR


My DC H10-60 headset is listed as having a “standard” input impedance of 150 ohms. Same for the AVCOMM AC-900 PNR. This is in contrast to say my regular music headphones (Sony 7506) which have an impedance of 63 ohms. Here are some sample Specs for my DC H10-60 aviation headset and the Sony 7506 monitor headset often used in studios.

David Clark H10-60 Specs
Impedance: Standard
NRR: 23dB
Earphone Type: Dynamic
Earphone Impedance: 150 ohms (300 each; wired in parallel)
Earphone Sensitivity: 90 dB SPL on flat plate coupler, re 1mW input @ 1KHz Earphone Frequency Response: 200-5,500 Hz
Earphone Plug: PJ-055 (.25" phone plug)

MDR-7506 Specs
Headphone Type: Dynamic, closed
Magnet Type: Neodymium
Driver Size: 40.0 mm
Frequency Response: 10Hz - 20 kHz
Impedance: 63 Ohms
Sensitivity (db): 106dB/mW
Power Handling Capacity: 1000mW

Obviously, some portable amps designed for non-aviation "headphones" and featuring different impedance specs may not functional optimally on a David Clark aviation "headset".

We also all know that aviation headsets have different input impedances, and there are impedance adapters to allow switching between military and civilian fixed wing for example. Whether for input or output, I'd like to avoid any form of impedance adapter.

Impedence Adapter:
http://www.mypilotstore.com/mypilotstore/sep/1979



So.................
Anyone using or knowledgeable about these devices, please post your thoughts and experiences.
Amp model recommendations would be appreciated.
I don’t need super-duper quality portable amp, but ruggedness and affordability are important to me.

You don't need an amplifier. You need an impedance matching circuit. The aviation headsets are all 300 ohm impedance. Most "normal" audio equipment is 5 to 7 ohms or less. That much impedance mismatch kills the volume.

MTV

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@MTV

Yup. I think you nailed it.
Based on your comments, I have been looking at impedance adapters at SKYGEEK.

http://www.skygeek.com/impedance-adapters.html

I did a little more reading, and you are quite right. The power loss into a mismatched low to high impedance load is major.

So it looks like an adapter it will be. The scanner is a Sony by the way, and I am not sure of the optimal headphone output impedance, but we will give the impedance adapter a go. Thanks for the feedback,

I could dig out a FORM 337 (Tuesday) for wiring a VHF marine radio into a TSO audio panel. Used for USCG aircraft and surface coms in a PA23-250C .

Worked great for monitoring the VHF marine radio in the aviation headsets but, still used the hand held microphone to transmit... Mostly because right seat crew would need to be with Honolulu Sector and left seat with ATC.

Don't know about your scanner, but I bought a headset adapter for my Vertex Standard (now Yaesu) handheld aviation transceiver, which works just fine without any additional thingy. It was an optional accessory when I bought the radio some 13 years ago. I can hear it well in the airplane using just my normal headset.

Cary

Cary,

Most aviation handhelds are set up to work with 300 ohm headsets, via the adapter that comes with them.

The problem comes when you try to use an I Pod or CB radio, or in our case, telemetry receivers with aviation electronics. Everything in the airplane is set up for 300 ohm impedance. Our telemetry receivers were all set up for 4 ohms, a serious impedance mis match. Plug a telemetry receiver in to MOST audio panels and crank the volume all the way up and you would just barely hear the audio.

I say most audio panels because in the last several years, some manufacturers of audio panels have built impedance matching circuits into their audio panels.

If you run into an impedance mismatch like this, you can crank the volume up with an amplifier, but you'll also amplify a bunch of noise....resulting in a crappy sound quality.

An impedance matching circuit is pretty simple. And they work wonders.

MTV

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MTV wrote:
An impedance matching circuit is pretty simple. And they work wonders.

Here is a link to a really simple calculator that allows you to plug in the impedances you are dealing with and to calculate a matching circuit.

Calculator of Impedence Matcher :
https://robrobinette.com/HeadphoneResistorNetworkCalculator.htm

Other Helpful Background Information:
http://www.head-fi.org/t/607282/headphone-amp-impedance-questions-find-the-answers-here
http://www.vwlowen.co.uk/radio/headphone2linein/headphones.htm

Denali wrote:

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MTV wrote:
An impedance matching circuit is pretty simple. And they work wonders.

Here is a link to a really simple calculator that allows you to plug in the impedances you are dealing with and to calculate a matching circuit.

Calculator of Impedence Matcher :
https://robrobinette.com/HeadphoneResistorNetworkCalculator.htm

Other Helpful Background Information:
http://www.head-fi.org/t/607282/headphone-amp-impedance-questions-find-the-answers-here
http://www.vwlowen.co.uk/radio/headphone2linein/headphones.htm

Good links....thanks.

MTV

mtv wrote:Cary,

Most aviation handhelds are set up to work with 300 ohm headsets, via the adapter that comes with them.

The problem comes when you try to use an I Pod or CB radio, or in our case, telemetry receivers with aviation electronics. Everything in the airplane is set up for 300 ohm impedance. Our telemetry receivers were all set up for 4 ohms, a serious impedance mis match. Plug a telemetry receiver in to MOST audio panels and crank the volume all the way up and you would just barely hear the audio.

I say most audio panels because in the last several years, some manufacturers of audio panels have built impedance matching circuits into their audio panels.

If you run into an impedance mismatch like this, you can crank the volume up with an amplifier, but you'll also amplify a bunch of noise....resulting in a crappy sound quality.

An impedance matching circuit is pretty simple. And they work wonders.

MTV

Yeah, I'm assuming that that's why I can plug just about any music source into my audio panel and it works fine. Mine is a PS Engineering 6000B. I had the avionics shop add an audio jack in the panel and another one in the back seat, so that music sources can be plugged into either and work off the aux circuits. I plug my XM radio into the panel jack to provide tunes while I'm flying, and the way it's wired, backseaters can plug a separate audio source into the backseat jack, and by using the pilot isolate switch, they can have their tunes and I can have mine.

Cary