[Elecraft] SO2R thoughts

[Joe Subich, W4TV]

> maybe it is because my hearing rolls off at 2500 to 2700 Hz very
> drastically which makes me wonder if those who have the difficulty
> have more a more normal hearing range and hi-fi speakers or headsets,
> thus could benefit with a low pass filter on the audio.

I've connected the front panel headphone output to an audio spectrum
analyzer good to over 25 KHz and seen no increase in the noise floor
(AF gain down) above the background -110 dB/hz at 100 Hz decreasing
to -130 dB/hz at 20 KHz.  There is no "hump" and fewer than a half-
dozen spikes to -100 dB representing clock/digital leakage.

By way of comparison, with the AF gain control at normal listening
levels (between 9:00 ad 11:00) the background noise in the 200 - 4000
Hz range is -50 to -60 dB/hz (all referenced to 1V p-p) and the
response drops quickly to the -115 dB/hz range between 2700 and 4500 Hz 
depending on the choice of roofing filter/DSP settings.

I can find *no* hint of "hiss" in the headphone audio of s/n 1450 ...
Yes, I can drive the headphone amplifier into distortion if I push
a -33 dBm signal into the antenna and turn the AF gain up well beyond
12:00 (as if I had inefficient headphones) but that's bordering on
abuse (still, it would be nice if the headphone amp were a bit more
"stout" than 100 mW/channel - particularly with the number of
headphones with greater 8 or 16 Ohm impedance - and the speaker
amplifier were a bit more than 3 W/channel.

73,

    ... Joe, W4TV


On 3/28/2014 1:44 PM, WILLIS COOKE wrote:
> Jim, like you, I have not experienced the harshness of the K3, but
maybe it is because my hearing rolls off at 2500 to 2700 Hz very
drastically which makes me wonder if those who have the difficulty have
more a more normal hearing range and hi-fi speakers or headsets, thus
could benefit with a low pass filter on the audio.
>
> Willis 'Cookie' Cooke, TDXS DX Chairman
> K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart
>
>
> ________________________________
>   From: Jim Brown <jim at audiosystemsgroup.com>
> To: elecraft at mailman.qth.net
> Sent: Friday, March 28, 2014 11:58 AM
> Subject: Re: [Elecraft] SO2R thoughts
>
>
> On 3/27/2014 7:25 PM, Stephen Bloom wrote:
>> another K3 ...Upside:  SO2R is most intuitive with identical xcvrs,
>> plays well with KPA500/KAT500, identical cabling  ...Downside:  Expensive,
>
> Consider a stripped down K3 for the 2nd radio. You don't need an antenna
> tuner, buy it without the 2nd RX, minimal filters.
>
>> It's more fun to have different rigs to play with, and like others, I find
>> the K3 can be kind of "harsh" to listen to for many hours.
>
> Gee, I haven't experienced that, and I've used mine for lots of long
> contests.
>
> 73, Jim K9YC
>
>
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