K3 DSP LPF daughterboard - What is an artifact and where can you find them?

[Don Rasmussen]

Thanks to Doug for the clarification of the hardware aspect of the DSP board upgrade. This has allowed me to do some research with my own K3's.

First of all, the term "artifact" seems to be used these days as a catch all. I have heard "rumbles", funny pops and ticks that were seemingly in the foreground of my IC756 and have taken a very negative view of this - DSP artifact generally means to me, odd beyond the point of accepting under normal conditions. I have analog ears, guys who got their first HF with DSP are probably okay with that type of thing.

I went searching for an artifact in the K3 transceiver having not encountered one before. I remembered that I had the upgraded DSP board for low range audio, but unfortunately a very early one that had no lettered marking on it at all, and no daughterboard. So, I was 99% confident that my K3 was ready to exhibit some artifactual behavior, and I would decide if it was objectionable enough to want the $24 upgrade LPF.

I searched NABBLE and found one of the first reports of this in early Spring to be sounding like "Jingle bells". Hmmm, never heard that. But I knew to look for "jingle bells" at approximately 4 khz and 78db down (weak). I put the K3 on 7 Mhz LSB at night and found a strong SWL signal. I went into the RX Eq and put all sliders at negative 16 EXCEPT number 8 (rightmost) which I put at +16.

What did I hear? "Sleigh Bells"!. That is quite different from Jingle Bells and although disappointed, it made more sense. ;-) It was plain as day - I am assuming I have found the artifact.

I pressed the CLR button to set the Rx EQ to FLAT, and I seriously could no longer hear this "artifact". I cant think of any scenario, ever when that rightmost EQ would be above ZERO. But for those that want to hear up there in dog whistle range, or those that can hear it naturally better than I can using a practical EQ setting, Elecraft has gone the extra mile. I hear as well as anyone as a reference, but as Doug suggests, the headphones may be a possible factor. I favor the speaker, 2 of them in fact.  

I applaude Elecraft for going to all the trouble and expense of engineering a daughterboard for this, and maintain once again that to my ears, K3 is the only IF DSP transceiver that sounds analog. The AGC is Q5, no artifacts in the foreground, and minimal DSP filter noise.

Just as a point of reference and no Icom bashing here, but Icom produced a document when the 756Pro was introduced, explained "rumble" and suggested that if you were the type to enjoy record albums, etc. - you may not like the sound of their transceiver. I have no idea what Elecraft did differently.  

I won't be adding the LPF mod - at $24 bucks. It's cost is trivial and I -enjoy- applying mods to my sets, but if there was ever a case of not broke don't fix, this is it for these ears.

73,
Don





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[Brendan Minish]

Don Rasmussen wrote:

> I applaude Elecraft for going to all the trouble and expense of
> engineering a daughterboard for this, and maintain once again that to
> my ears, K3 is the only IF DSP transceiver that sounds analog.

For those of us with good hearing to 12KHz and above really appreciate
that elecraft have taken the time to understand the relativity subtle
issue that some of us were hearing, create a mod to add the LPF and that
this is now standard.
Not everyone can hear the issue, or will be bothered by it, it's quite
subtle but it was certainly fateuging to some of us who can hear well at
higher frequencies. I had initially added an R/C Low pass filter to my
headphone ear pieces which worked but the LPF mod does a better job, I
was one of the beta testers for it.


Incidentally the D to A chip in the K3 is performing well within it's
design specs for aliasing products, I have a portabe MP3 player that is
nearly unusable to my ears for listening to practice CW stored as MP3
files with a bit rate of 12Khz (You can get a lot of hours of Ebooks
converted to CW at lower sapmle rates)

73
Brendan EI6IZ
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[N8CEP]

I would imagine there are a lot of us who hear the "artifacts" but just don't
realize it? This would account for the undefinable  "fatigue" some talk about.

Keith W8GX




On Jan 2, 2010, at 9:21 PM, Brendan Minish wrote:

> Don Rasmussen wrote:
>
>> I applaude Elecraft for going to all the trouble and expense of
>> engineering a daughterboard for this, and maintain once again that to
>> my ears, K3 is the only IF DSP transceiver that sounds analog.
>
> For those of us with good hearing to 12KHz and above really appreciate
> that elecraft have taken the time to understand the relativity subtle
> issue that some of us were hearing, create a mod to add the LPF and that
> this is now standard.
> Not everyone can hear the issue, or will be bothered by it, it's quite
> subtle but it was certainly fateuging to some of us who can hear well at
> higher frequencies. I had initially added an R/C Low pass filter to my
> headphone ear pieces which worked but the LPF mod does a better job, I
> was one of the beta testers for it.
>
>
> Incidentally the D to A chip in the K3 is performing well within it's
> design specs for aliasing products, I have a portabe MP3 player that is
> nearly unusable to my ears for listening to practice CW stored as MP3
> files with a bit rate of 12Khz (You can get a lot of hours of Ebooks
> converted to CW at lower sapmle rates)
>
> 73
> Brendan EI6IZ
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> Please help support this email list: http://www.qsl.net/donate.html
>

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[Julian, G4ILO]

Keith Hamilton-3 wrote

I would imagine there are a lot of us who hear the "artifacts" but just don't
realize it? This would account for the undefinable  "fatigue" some talk about.

You can see these "artifacts" with a program like Spectran, but they are only present when modulation is present and they are at a very low level, probably no worse than the THD of budget consumer audio products. As someone said to me in an email recently, they probably wouldn't be an issue if people used communications headphones and speakers with their radios instead of hi-fi models.

[Brendan Minish]

there are few if any pairs of 'communications' phones that have
significant attenuation above 10Khz yet retain good flat frequency
response over the range we are interested in (~ 100Hz to 4KHz )

the artefacts are aliasing products centred around 12Khz, since these
are not harmonically related to the fundamental audio the ear is pretty
sensitive to them, even though they are at least 60dB lower than the
wanted audio.

As I have pointed out before, It's subtle, you are not going to hear
this at all if you have HF hearing loss,  the D to A chip is performing
per spec and the K3 prior to this change is already better than a lot of
the competition.  

73
Brendan EI6IZ

On Sun, 2010-01-03 at 03:20 -0800, Julian, G4ILO wrote:

> Keith Hamilton-3 wrote:
> >
> > I would imagine there are a lot of us who hear the "artifacts" but just
> > don't
> > realize it? This would account for the undefinable  "fatigue" some talk
> > about.
> >
> You can see these "artifacts" with a program like Spectran, but they are
> only present when modulation is present and they are at a very low level,
> probably no worse than the THD of budget consumer audio products. As someone
> said to me in an email recently, they probably wouldn't be an issue if
> people used communications headphones and speakers with their radios instead
> of hi-fi models.
>
> -----
> Julian, G4ILO. K2 #392  K3 #222.
> * G4ILO's Shack - http://www.g4ilo.com
> * KComm - http://www.g4ilo.com/kcomm.html
> * KTune - http://www.g4ilo.com/ktune.html
>

--
73
Brendan EI6IZ

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[Don Wilhelm-4]

Brendan,

Not to be argumentative, but some with HF hearing loss may be bothered
by this distortion even though it is low level and is not in the range
of conscious hearing.  When I first became aware of my HF hearing loss,
I found that I was increasingly irritated by low grade audio devices
because of the THD.  It seems I can 'sense' the distortion even though I
cannot actually hear in that range.  Strange as it may seem, I went on a
quest for better fidelity in sound as my hearing loss became worse.  I
have mentioned this phenomenon to several knowledgeable dealers in audio
equipment as well as my audiologist and they have confirmed what I have
observed.  If the hearing loss is across the full spectrum, the
increased perception of distortion is not present.  My lower range
hearing remains normal, and my audiologist tells me that is an unusual
condition, so that may have something to do with my perceptions.  I will
put the LPF on my K3, 'just in case'.

73,
Don W3FPR.

Brendan Minish wrote:
> As I have pointed out before, It's subtle, you are not going to hear
> this at all if you have HF hearing loss,  the D to A chip is performing
> per spec and the K3 prior to this change is already better than a lot of
> the competition.  
>  
>
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