[Elecraft] K3/MMTTY/Signalink Problem

[Joe Subich, W4TV]

> The manufacturer said the slider must be at max and then use the
> front panel pot and radio line in control to manage the desired audio
> level.

The problem is that when the Windows slider is at max the USB CODEC is
running rail to rail on its output.  With the improper filtering and
lack of regulation for the V/2 reference the output tones *are clipped*
and that causes distortion no matter where one runs the front panel
controls on the device or the mic gain on the K3.

This is another design fault of the device, the gain of its internal
VOX/PTT should have been increased to operate at lower levels from
the CODEC.  With the K3, one is better served to use a lower output
from the CODEC and higher mic gain/VOX gain in the K3 and not rely
on the internal VOX/PTT of the device - transmit audio quality will
be up to 3 dB better.

73,

    ... Joe, W4TV


On 2014-10-15 10:46 AM, Greg wrote:
> Understood...thanks.
>
> I had a similar problem when I first got a SL USB.  The manufacturer said
> the slider must be at max and then use the front panel pot and radio line
> in control to manage the desired audio level.  When I did that I was able
> to get the desired output.  I did not mean to crank all the controls to
> max....that indeed would be a mess.
> On Wed, Oct 15, 2014 at 7:34 AM, Joe Subich, W4TV <lists at subich.com> wrote:
>
>>
>> Be very careful ... Signalink USB lacks sufficient bypassing on
>> the internal 5V distribution, lacks regulation on the CODEC and
>> op-amp V/2 reference, and lacks sufficient filtering on the USB
>> power line.
>>
>> Most sound card show increased distortion with Playback gain above
>> 80%.  Cranking the audio gain to 100% in the playback mixer can
>> cause it to become *VERY DIRTY* if power supply and regulation is
>> not properly addressed.
>>
>> 73,
>>
>>     ... Joe, W4TV
>>
>>
>>
>> On 2014-10-15 10:03 AM, Greg wrote:
>>
>>>   Another thing to check:
>>>>
>>>> In your sound devices find the signalink USB codecs and open the playback
>>>> mixer.  The slider needs to be at 100....all the way to the top.
>>>>
>>>> Also, there are jumpers in the SL.  One is for low output or high output.
>>>> Make sure the jumpers are set to the high positions.
>>>>
>>>> 73
>>>> Greg
>>>> AB7R
>>>>
>>>>
>>>
>>>
>>>
>>>>
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>