[TenTec] New Orion I v2 Firmware version: 2.062a

[Dr. Gerald N. Johnson]

On Sat, 2007-05-26 at 10:58 -0400, wa3fiy at radioadv.com wrote:
> On 26 May 2007 at 10:25, K4IA at aol.com wrote:
> 
> >  
> > Sidetone audio is tinny.  Sounds like a set of old headphones I had  with a 
> > metal diaphragm.  Very fatiguing to listen to.  
> >  
> 
> Interesting!   I have about a dozen different headsets around here from aircraft style to 
> Koss stereo HiFi, various types from the FM broadcast station and two pairs of Trimm 
> Professionals, the ones with a metal diaphragm.  Guess which I prefer on CW?  Yep, the 
> Trimm's.  They have a nice clean, crisp sound unmatched by all the others.  Very 
> uncomfortable though until I found some Radio Shack foam pads that fit perfectly.
> 
> Just goes to show how different our preferences are and what challenges equipment 
> designers have in designing equipment that works well for all users.  A lot more difficult 
> job than we might think.
> 
> Everyone have a nice Memorial Day and please remember and honor those who gave 
> their lives that the rest of us could be free.
> 
> 73,
> 
> -Lee-
> WA3FIY
> 
> 
Could it be that the modern low impedance (4 to 8 ohm) headphones take
so little voltage drive that turning down the DSP headphone drive leaves
it using so few bits of the digital level that you hear the granularity
of 4 bit audio? The Trimms would be high impedance and take more voltage
to give enough power to be heard and so use many more bits at the
digital level, maybe 14 or 15 and so the digital granularity would be
hard to hear.

Could it be that the low impedance headphones need to be driven through
a 250 ohm resistor? Or a 50L6 output transformer (2K to voice coil)?

I'm thinking the large voltage driven headphones won't hear the buzz or
the clicks at the end of the sidetone.

To say nothing about the inherent resonant bandwidth of the Trimms is way
narrower than the hifi headphones. Hearing to 10 Hz only passes rumbles 
indicative of inadequate power supply bypassing (Icom PRO series) and
hearing to 24 KHz only passes circuit hiss, neither of which adds to 
communications.

-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer