Hello Bob,

I carried out a properly-loaded frequency analysis of these transformers. The frequency response is flat from 15 Hz to 10 kHz, only down 1.4 dB at 20 kHz; the upper -3 dB point is at 33 kHz. Consequently, this transformer could easily be considered Hi-Fi. So, you could use this transformer to provide Galvanic isolation for your low-impedance headphones from a Hi-Fi amplifier.

73 de Brian, VK2GCE

From: [email protected] [mailto:[email protected]] On Behalf Of Bob Groh
Sent: Monday, 27 September 2021 8:23 AM
To: ARC-5 Maillist
Subject: [ARC5] Headset adapters MC-385-B and MC-385-C

Cleaning up the ham shack and found these two items - would like to find a home for them so I don't do something stupid like taking them apart for the parts. These are apparently nothing more than impedance converters for headphones (e.g. HS-33). Order number on one is "148-DAY-44" which  I assume that the original order was written at the tail end of WW II. Just cover the postage ($8??) plus a couple of bucks and I will be a delighted ham.

Bob Groh, WA2CKY