What is the allowable headset impedance

[pradeep]

Hello all,

 

I am a student pilot learning to get my recreational license.

 

Recently I bought a DC headset which was actually designed for railroad applications. From its circuit diagram I found out that it has 2 nos 275ohm series connected earphones. It came with low to high impedance adaptor.

 

But I thought as the earphones are already on high impedance (550ohm total) I can take off the impedance transformer, and also thinking of connecting the earphones in parallel to make it 137.5ohms which is approximately equal to DC's other headsets - 150ohm).

 

Before doing this I am just wondering what would be the supported earphone impedance range a radio on recreational airplane will support. I read somewhere that it is possible it can support between 600ohms to 150ohms. If so I need not have to convert the earphones into parallel.

 

Your valuable comments and advice re this will be highly appreciated.

 

With advance thanks,

 

Pradeep

 

 

[BigPete]

G'day Pradeep, there's a fair chance the radio you hook into will be a Microair 760.

 

Try looking here:

 

www.microair.com.au

 

regards

 

 

[sseeker]

I don't know whether this has anything to do with what you're after, but keep in mind you don't actually plug your headset into the radio, you plug it into the intercom. Unless you're flying a single seater or an AC with no intercom of course...

 

 

[pradeep]

I don't know whether this has anything to do with what you're after, but keep in mind you don't actually plug your headset into the radio, you plug it into the intercom. Unless you're flying a single seater or an AC with no intercom of course...

Sorry if I am unclear on my explanation of my question.

 

My worry is whether I can use a high impedance (550ohm) earphone headset with a recreational intercom / radio without any modifications? The usual DC headsets are 150ohm impedance.

 

The type of plane is Tecnam P92 Echo Super.

 

Thanks for your replies.

 

 

 

[sseeker]

That's fine pradeep, I was just unsure whether my explanation was correct. When you plug your headset into the aircraft you actually plug it into the intercom, not the radio (for a 2 seater aircraft).

 

 

[jetboy]

The nominal impedance radios and intercoms are made for aircraft is 600 ohms, most will be satisfactory with much lower. If you needed to drive domestic headphones such as 8 ohms then use the speaker output (check required as some spkr outputs must not be grounded).

 

If your volume level is too low with the DCs in series, it may go up with parallel. Some intercoms just parallel all outlets so you can only go so far with the cheap ones.

 

Ralph

 

 

[pradeep]

The nominal impedance radios and intercoms are made for aircraft is 600 ohms, most will be satisfactory with much lower. If you needed to drive domestic headphones such as 8 ohms then use the speaker output (check required as some spkr outputs must not be grounded).If your volume level is too low with the DCs in series, it may go up with parallel. Some intercoms just parallel all outlets so you can only go so far with the cheap ones.

 

Ralph

Thanks Jetboy

 

I took off the impedance transformer and attached a volume controller. I will check how it feels with 550ohms on my next training session and keep posting.

 

Thanks again,

 

i_dunno

 

 

[pradeep]

Tonight I had the chance to check my headset. Wow what a performance.

 

The volume was excellent and now I can hear my instructor very well.

 

Tonight we did the stalls. pheeww finally back to normal...

 

Thank you all for posting replies re my concerns.

 

Now I am happy with my David Clark Headset with some modifications...!

 

As a note: if you are using a headset impedance adopter first please check your headset's original impedance and make modifications to suit.

 

Cheers,

 

Pradeep