DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 18 Jul 2018, 20:31

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 6 posts ] 
Author Message
PostPosted: 04 May 2017, 22:21 
Offline

Joined: 04 May 2017, 20:35
Posts: 3
I'm new here and not knowledgeable about circuits. Please forgive my ignorance on circuit boards and circuit theory.

I bought an Aviation headset from a Chinese manufacturer. It does not work as expected when plugging in auxiliary music to it. So I have some questions. First I'll give background on what I know about Aviation headsets and then I'll ask the questions. (For those not detail oriented you can probably skip the background part.)

Background on Aviation headsets:
Aviation headsets have both speakers and a microphone. Airplanes use a dual plugs (one for speakers and one for the microphone). Helicopters (and I think military aircraft) use a single plug with many rings. The resistance the headphones give should be 300 to 600 ohms (not like the standards around the house of 8 or 32 or whatever low impedance they have). The microphone is up at least that high if not higher, seems like I may have read 1,000 ohms at some point, it also I've read that the microphone's resistance should be close to the headphones resistance so I'm not sure about that 1,000 ohm remark. I think my point about the resistance is that Aviation audio panels and headsets are not like other audio equipment in that respect. Aircraft (both planes and helicopters), have an intercom system as well as a PTT (Push To Talk) button to transmit. the microphones are auto-squelched and all you have to do to talk to your co-pilot is just start talking, but to transmit over the radio, you have to press the PTT button. There are volume controls on each radio and on the intercom, as well as most headsets have their own volume control.
Hopefully that's enough background info to give a general idea of how headsets, audio panels, and radios are set up in an airplane.

A little more info and the questions:
The headset works great until you plug an auxiliary audio source into the side of its volume control box. Once I've done that, the volume is so low on both the speakers and the microphone that I can't hear my copilot and he can't hear me talking into my microphone. I own more expensive headsets that work great with auxiliary audio sources. No change at all in the intercom. I really want to make these cheaper headsets work.

1) Can I get somebody to redesign a circuit board for me? Who or where do I go to look for that?

2) I pulled the cover off the volume control box to look at the circuit board and noticed the ground for the left speaker, the right speaker, and the microphone were all put together into one ground.
Shouldn't the microphone's ground be kept separate? Or is this normal? (I'm on the road and will take apart my more expensive headsets when I get home.)

More info:
I'm not sure why the microphone wires even run through the circuit board at all unless it's to add resistance to it in order to make the resistance the correct amount. I can't trace the whole path without removing components. I've talked with the manufacturer about the issue and he wants to add resistance to the audio input. He sent me an aux cable that he added a resistor to and said if it works, then he would add the resistor to the circuit board. I'm just thinking that the auxiliary cable shouldn't affect the airplanes intercom at all.

3) Shouldn't all these circuits be better isolated from each other? (If you ask me what circuits?, I'm not sure I know.)

4) Shouldn't the speakers be on one circuit, the microphone another (including separate grounds), and the auxiliary input be designed in such a way that the user has no idea the cable is plugged in other than the music coming through it? (It is a 3 ring / 4 connections plug so that you can plug a cell phone in and talk through it.) I mean I know it should be because I have headsets that work that way. I know the first half of this question was basically asked in #3 already.

I'll probably have more questions but let's just start with that. Don't be too harsh on me lol.


Top
 Profile  
 
PostPosted: 19 May 2017, 08:31 
Offline

Joined: 26 Oct 2012, 21:00
Posts: 190
Location: ontario canada
there's a lot more than meets the eye when it come to avionic communication systems.
as they are duplex(two way) in real time and noise canceling with a mix of priority switching to boot.

without more details of both the device your trying to connect and the particular headset you have it sounds like some signal manipulation so as to not load down the aux input is required.

it may be as simple as the added resistance solution you've been offered but a buffer or x-former could also provide a resolution.(not to mention phantom power requirement to enable devices and assign priorities)

i'm not the most versed on aviation communication systems but have worked for a contractor both installing and repairing com and radio systems for various transportation systems(including aircraft).
are you certain a cellphone patch to the aux input of the com system of a plane is allowed without authorization? i'm not clear as to the regulations but to my knowledge any signal device added to the "pilot's com" system(other than existing devices like signal beacons, markers or audible alarms)has to be pre-authorized. i'm not going to make this a sticking point because that's your ball of wax to deal with.

and as it's impossible to cover all device configurations and possibilities when it come to designing an "input" stage you will have to specify a device or a range of allowed types of devices to narrow down a "solution".


Top
 Profile  
 
PostPosted: 19 May 2017, 20:48 
Offline

Joined: 04 May 2017, 20:35
Posts: 3
Thank you so much for your reply. I own or have owned both Bose and Lightspeed headsets. These 2 brands are the biggest brands in noise-canceling headsets. I don't know the actual statistics but I'd guess that David Clark is #1 in passive noise reduction and #3 in active noise reduction headsets (noise-canceling).

I know the first 2 companies both design headsets that have auxiliary input as well as Bluetooth for your cell phone. What's the regulations? I'm not sure what the regulations are when it comes to the manufacture of these headsets but I know the big brands do it, and are FAA approved headsets. These brands also do it in such a way that it works across all or most U.S. aircraft.

The range of devices connecting the aux input on the headset would be current day cell phones, tablets, & MP3 players such as iPods.
What details do you need about the airplanes? What details do you need about the headset?

Thanks.


Top
 Profile  
 
PostPosted: 22 May 2017, 20:49 
Offline

Joined: 26 Oct 2012, 21:00
Posts: 190
Location: ontario canada
can you give me the make and model of the headsets in question?


Top
 Profile  
 
PostPosted: 24 May 2017, 00:17 
Offline

Joined: 04 May 2017, 20:35
Posts: 3
Sure.
Yueny ANR AH-6000


Top
 Profile  
 
PostPosted: 24 May 2017, 20:39 
Offline

Joined: 09 Oct 2012, 19:43
Posts: 292
Location: Vancouver Canada
Perhaps this might help.
http://www.vansairforce.com/community/s ... p?t=136375
I did a search for aviation headset wiring.
https://www.google.ca/search?q=wiring+l ... OJCF1PK1dM:


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 6 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 4 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy