Impedance matching
Thread Starter
Impedance matching
I have a Peltor with a round (electret ?) microphone, which I'd like to use interchangeably with headsets in a helicopter with no intercom which have dynamic (squarer ?) microphones.
I've seen impedance matchers for sale on the internet, but need guidance as to which to get (a new headset is out of the question for the moment).
Do I need to convert from high to low, or low to high ? And can anyone recommend a suitable source for an adapter which has a standard UK helicopter socket input AND output ?
Or is microphone replacement feasible ?
I've seen impedance matchers for sale on the internet, but need guidance as to which to get (a new headset is out of the question for the moment).
Do I need to convert from high to low, or low to high ? And can anyone recommend a suitable source for an adapter which has a standard UK helicopter socket input AND output ?
Or is microphone replacement feasible ?
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Impedance
I'm not expert in this matter but few years ago I tested my helmet (Gentex SPH 4) on a Lama. The mic was not working. I swapped the 2 pins mic with the one from the headset and seemed to work properly.
Again, I'm not sure, I think the headset was a Clark. The mic were different only in the shape (and in the impedance of course).
I don't remember wether Peltor headset has a detachable mic or not, but if you have a 2 pins detachable mic, I would just try and if it works, test it properly or talk to a certified avionic engineer, just to be safe and legal.
Ciao ciao.
Again, I'm not sure, I think the headset was a Clark. The mic were different only in the shape (and in the impedance of course).
I don't remember wether Peltor headset has a detachable mic or not, but if you have a 2 pins detachable mic, I would just try and if it works, test it properly or talk to a certified avionic engineer, just to be safe and legal.
Ciao ciao.
Try asking Headset Services at Shoreham. They should be able to give you the definitive answer (and sell you the required bits, I imagine).
A quick google will produce their URL & contact details.
HTH
A quick google will produce their URL & contact details.
HTH
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Oh boy I think you have a tiger by the tail and an expensive bit of gear that might be far cheaper to supplement than the other way around.
Swapping the polarity of the dynamic and electric mikes (i think we used to call them the small grey or green ones) used to work wonders some times and throwing the old carbon mikes out the window was equally effective when they just cut up bad.
the earphone impedance match is a particular bugbear of mine especially when the military ex's used to jump into a civilian machine with their "off the back of a truck green brain bucket." Either:-
1) one of us couldn't hear a damm thing or,
2) the expensive radio used to stop working with a tell tale puff of smoke, and guess who had to pay megabucks to fix it?
One found it was a good idea to purse your lips aginst the mike if someone new got in, regardless of what he told you about which flash harry radio-tech had fixed his headset, and see if it was warming up.
If so, quickly swithch radios off, disconnect him completely, wait till everything cooled down then go back on with you only and hope that the radio wasn't going to throw a puff of smoke.
my advise to you would be, you seem to have what is supposed to be an expensive microphone, go to an expert, match it properly with the civilain radios and earpieces of the local network, or if he says keep it for the grandkids, then throw it out the window.
that will be the cheapest option.
cheers tet.
Swapping the polarity of the dynamic and electric mikes (i think we used to call them the small grey or green ones) used to work wonders some times and throwing the old carbon mikes out the window was equally effective when they just cut up bad.
the earphone impedance match is a particular bugbear of mine especially when the military ex's used to jump into a civilian machine with their "off the back of a truck green brain bucket." Either:-
1) one of us couldn't hear a damm thing or,
2) the expensive radio used to stop working with a tell tale puff of smoke, and guess who had to pay megabucks to fix it?
One found it was a good idea to purse your lips aginst the mike if someone new got in, regardless of what he told you about which flash harry radio-tech had fixed his headset, and see if it was warming up.
If so, quickly swithch radios off, disconnect him completely, wait till everything cooled down then go back on with you only and hope that the radio wasn't going to throw a puff of smoke.
my advise to you would be, you seem to have what is supposed to be an expensive microphone, go to an expert, match it properly with the civilain radios and earpieces of the local network, or if he says keep it for the grandkids, then throw it out the window.
that will be the cheapest option.
cheers tet.
t
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Get a david clark headset H 10-66 with a low/hight impedance switch. I have flown many different helicopter types (Bell, EC, Sikorsky, AW) with this one headset and no problems.
I plan only to fly one type from now on so if you want a good second hand one just PM me.
I plan only to fly one type from now on so if you want a good second hand one just PM me.
Thread Starter
Thanks for the replies. To summarise:
Headset Services is either the dog's bollocks or dog sh1t. But they might have an answer.
"Buy a new Dave Clark" - despite the fact I can't afford one right now, and I think I said that originally, and despite the fact I personally don't get on with them.
Plan A is a manual approach - take my headset and a similar one from the pool out to the aircraft - until funds allow a new one. Hey ho.
Headset Services is either the dog's bollocks or dog sh1t. But they might have an answer.
"Buy a new Dave Clark" - despite the fact I can't afford one right now, and I think I said that originally, and despite the fact I personally don't get on with them.
Plan A is a manual approach - take my headset and a similar one from the pool out to the aircraft - until funds allow a new one. Hey ho.
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I also have a question about impedance matching, which I am hoping somebody may be able to help with.
I'm currently using a high impedance headset in a low impedance avionics fit by using a battery-powered impedance converter.
I would like to do away with the impedance converter (it chomps through batteries).
I can source a 5ohm microphone, but do I need to do anything to do the speakers?
I'm currently using a high impedance headset in a low impedance avionics fit by using a battery-powered impedance converter.
I would like to do away with the impedance converter (it chomps through batteries).
I can source a 5ohm microphone, but do I need to do anything to do the speakers?
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The short answer is: it depends.
You're probably ok with the existing speakers, but you might not be - you really want to have a chat to the maintenance techs who look after your avionics to find out exactly what's in there.
Additionally, the high/low impedance categorisation masks the fact that the microphone technologies are actually very different, and there are several different ones around. The reason the high-headset-to-low-aircraft needs a battery is that the standard high-Z electrets need to be line powered, but the (low-Z) carbon mics don't.
Most of the major headset manufacturers do a low-Z version, which they'll sell you on demand. However, not all of them offer a field-switchable solution: Lightspeed, for example, can only be changed over by the factory (in the USA, no less), and they won't send you the bits. If the converter box works for you, it might be worth seeing whether you can find an aux power output to plug it into: some aircraft have lighter (or similar) plugs supplying 12V; add a monolithic 9V reg and you don't need the battery.
You're probably ok with the existing speakers, but you might not be - you really want to have a chat to the maintenance techs who look after your avionics to find out exactly what's in there.
Additionally, the high/low impedance categorisation masks the fact that the microphone technologies are actually very different, and there are several different ones around. The reason the high-headset-to-low-aircraft needs a battery is that the standard high-Z electrets need to be line powered, but the (low-Z) carbon mics don't.
Most of the major headset manufacturers do a low-Z version, which they'll sell you on demand. However, not all of them offer a field-switchable solution: Lightspeed, for example, can only be changed over by the factory (in the USA, no less), and they won't send you the bits. If the converter box works for you, it might be worth seeing whether you can find an aux power output to plug it into: some aircraft have lighter (or similar) plugs supplying 12V; add a monolithic 9V reg and you don't need the battery.
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Thank you all for your replies. I have tried contacting a few different companies with limited success. However I can source replacement microphones once I know what I need. While the aux power outlet would be a nice solution I'm not sure its feasible with the fleet size.
My current microphone is a 50 ohm Electret.
I'm surmising I need to try a 5 ohm Dynamic, which I've seen in M87 and M101 flavours...
My current microphone is a 50 ohm Electret.
I'm surmising I need to try a 5 ohm Dynamic, which I've seen in M87 and M101 flavours...
Last edited by longtime lurker; 25th Jun 2011 at 22:37.
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Lightspeed Mics
Hi Guys
I am flying some old millitary spec helis in Africa and have an issue with my Mic on the Lightspeed Zulus. It doesn't seem to work on these machines - aparently it's a common thing with these older military machines.
Anyone have any suggestions on what to do about this. On the DC's, the other guys were able to swop the mics, however Lightspeed hasn't replied to any of my emails.
Thank in advance guys.
I am flying some old millitary spec helis in Africa and have an issue with my Mic on the Lightspeed Zulus. It doesn't seem to work on these machines - aparently it's a common thing with these older military machines.
Anyone have any suggestions on what to do about this. On the DC's, the other guys were able to swop the mics, however Lightspeed hasn't replied to any of my emails.
Thank in advance guys.
