[ARC5] [Milsurplus] Audio Impedance Matching on USAAF aircraft

[Dennis Monticelli]

The headset adapter Is MC-385-C (says for use with Headset HS-33 or
HS-38).  It is an autotransformer stepdown to 600ohms. I measured
6600ohm input Z when loaded with 600ohms.  Mine is made by Rola under a
1944 order.  1/4" male in and 1/4" female out.

Here is a pic I borrowed from eBay.  Quicker than photographing mine.
[image: image.png]

Dennis AE6C

On Tue, Dec 30, 2025 at 6:44 PM Hubert Miller <Kargo_cult at msn.com> wrote:

> 8000 ohms seems so old-world, like 1920s radio.
> I have some kind of small ‘impedance adapter’. I don’t know where it is
> right now or the item designation.
>
> But i think it’s nothing but a pot inside.
>
> -Hue Miller
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: https://www.qsl.net/donate.html
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20251230/15f8cec4/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 413484 bytes
Desc: not available
URL: <http://mailman.qth.net/pipermail/arc5/attachments/20251230/15f8cec4/attachment-0001.png>