GA to 8ohm Headphone Adapter Completed

[Gary G]

Having posted to this group before, I though I would just provide
the follow up.

I completed a transformer design - thanks for people who
posted in the group with information.

Instead of paying $75 - $150 for an adapter, I constructed
what is the equivalent of 500 ohm source impedance to
4 ohm (actually, 2 8-ohm earbuds in parallel) adapter.
I've tested the unit and am quite happy with it.

I used a stereo 1/4" male adapter cable into a 3-piece
PVC tube assembly (2 end caps and a 3" piece - stock off
the shelf from Home Depot).
I used a Radio Shack $2.99 audio transformer and using
my old engineering days book, insured that I had the right
impedance transformation ratio.

Not including my labor (hee hee), I spent a grand total
of approximately $7 in parts.

In general, most aviation radios expect too see 200-ohm to 600-ohm
loads. Higher loads are typically fine, but lower isn't a good idea.
If one uses 16-ohm headphones or 32-ohm headphones (not uncommon
at all), the load impedance seen by the radio is higher.
This prevent excessive current loading, but higher will affect
"optimum" power transfer. It is safe, nonetheless.

The reason I did this: As an engineer and musician for a music company,
I have some very high-end custom molded, in-ear headphones that
I found are very comfortable and work very well in the plane.

Now - I have to obtain a boom mic to use . . .that hasn't been
as easy as it sounds for my "low budget" approach . . .

I thought some of you might be interested to hear how I finished that up.

Good flying!

Gary

[Michael Ware]

Shorty's used to sell one that was built inside a 35mm plastic film
container. Plug on one end, jack on the other. WAAAAYYY overpriced, of
course.

"Gary G" > wrote in message
...
> Having posted to this group before, I though I would just provide
> the follow up.

> I used a stereo 1/4" male adapter cable into a 3-piece
> PVC tube assembly (2 end caps and a 3" piece - stock off
> the shelf from Home Depot).
> I used a Radio Shack $2.99 audio transformer and using
> my old engineering days book, insured that I had the right
> impedance transformation ratio.
>
> Gary

[RST Engineering]

And they stole the design from an article I wrote in Kitplanes some ten to
fifteen years ago on exactly the same subject with exactly the same design
with exactly the same parts, including the film canister.

Jim


"Michael Ware" > wrote in message
...
> Shorty's used to sell one that was built inside a 35mm plastic film
> container. Plug on one end, jack on the other. WAAAAYYY overpriced, of
> course.

[Matt Whiting]

RST Engineering wrote:
> And they stole the design from an article I wrote in Kitplanes some ten to
> fifteen years ago on exactly the same subject with exactly the same design
> with exactly the same parts, including the film canister.
>
> Jim
>
>
> "Michael Ware" > wrote in message
> ...
>
>>Shorty's used to sell one that was built inside a 35mm plastic film
>>container. Plug on one end, jack on the other. WAAAAYYY overpriced, of
>>course.
>
>
>

Did you let'em know that you knew? :-)

Matt

[Gord Beaman]

"RST Engineering" > wrote:

>And they stole the design from an article I wrote in Kitplanes some ten to
>fifteen years ago on exactly the same subject with exactly the same design
>with exactly the same parts, including the film canister.
>
>Jim
>
One would think that you, being a ham, would have used one of
the aluminum canisters for RF shielding vice the modern plastic
unit. I can only assume that you told them the little trick of
getting the cap of the metal unit on?
--

-Gord.
(use gordon in email)