[Elecraft] K3s DSP headroom

[Joe Subich, W4TV]

On 9/20/2016 7:59 AM, brian wrote:
 > I seem to recall this advice (from Elecraft?):
> Use the attenuation sides of the equalizers and not the gain side if
> at all possible.

Yes, this came from Lyle, KK7P who designed the DSP.

 > This begs the question.  If gain is bad to use, then why is it (up to
 > +16 db) included as a choice.  Why not limit it to some small value?

His commend was not to use large values of boost across the passband.
one band of significant boost should not be an issue unless it is in
the middle of the passband.  For example, I have experimented with
some rather aggressive high frequency boost profiles (-16, -16, -6,
0, 0, 6, 10, 12) without apparent problem but aggressive mid-range
boost (-16, -16, 0, 10, 10, 10, 13, 15, 16) results in obvious
distortion.

73,

    ... Joe, W4TV

On 9/20/2016 7:59 AM, brian wrote:
> I seem to recall this advice (from Elecraft?):
> Use the attenuation sides of the equalizers and not the gain side if at
> all possible.
>
> This begs the question.  If gain is bad to use, then why is it (up to
> +16 db) included as a choice.  Why not limit it to some small value?
>
> It would seem this area is ripe for some real measurements.
>
> 73 de Brian/K3KO
>
> On 9/20/2016 11:02 AM, Ramon Tristani wrote:
>> Important question. Could the designer from Elecraft please answer?
>>
>>
>>
>> Sent from my iPhone
>>
>>> On Sep 20, 2016, at 6:12 AM, f1gwr <f1gwr at free.fr> wrote:
>>>
>>> Question for the K3s DSP programmer(s):
>>>
>>> After reading the "audio" thread and trying to optimize my audio
>>> equalizer, my questions are: what is the headroom over the 0 dB
>>> equalizer? Or does the DSP has its own normalizer/AGC to avoid overload?
>>>
>>> Found a satisfactory setting, with maximum values being set to 0 dB
>>> in the voice band (300-3 k), and consequently have to turn the volume
>>> halfway in a calm room (audio preset= high).
>>>
>>> My concerns are:
>>> - not clipping the AF while overflowing the DSP, namely registers
>>> during calculations.
>>> - getting enough AF gain so to have sufficient audio power especially
>>> in noisy environments.
>>>
>>> Said in another way what is in practice the maximum safe gain
>>> settable in the equalizer?
>>>
>>> VY 73,
>>> Christian F1GWR in JN38SN
>>> K3s groupie
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