[Boatanchors] Headphone Impedance Matching

[mac]

Sounds like your Telex 600 ohm unit simply has a broader frequency  
response than either the speaker or the 2000 ohm headset.....

Dennis D.  W7QHO
Glendale, CA

**********
On Dec 5, 2013, at 4:43 AM, David C. Hallam wrote:

> OK, next question about my headphone impedance matching.  I have  
> listened to the audio from my 75S-3 in three different ways.
>
> 312B-4 Collins speaker
> Telex 600 ohm impedance headphones
> Lincoln/Telex 2000 ohm impedance headphones
>
> When using the Telex 600 ohm headphones and the audio gain turned  
> all the way down, I hear a distinct hum.  I do not hear this hum  
> with either of the other two.  Any explanation of why I hear it only  
> with the 600 ohm headphones?
>
> David
> KW4DH