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K3 Audio Response - Version 3.33 Firmware

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P.B. Christensen

K3 Audio Response - Version 3.33 Firmware

I have attached links to three .JPG images of the K3's audio response as
measured at
the headphone jack with SpectraPlus FFT software. Response passband was
normalized for both modes. SSB
is measured through the 6K filter, and CW through the 8-pole 2.8 kHz filter.
However, V3.33 SSB was taken with Fc = 1.35.

It would have made more sense to capture the responses such that three SSB
plots would overlay on one graph and three CW plots on a second, but that
took too much time in waiting for the firmware to load between plots.
Still, you can see radical differences between firmware versions in the
kinks below. Rx Band-1 EQ seems operational now too :-)).

http://216.229.20.37/images/K3-V325.jpg
http://216.229.20.37/images/K3-V330.jpg
http://216.229.20.37/images/K3-V333.jpg

As you can see, CW with V3.25 has the strongest low-end response relative to
1 kHz, but that can be compensated for with the first two EQ bands. Even as
it is, if you draw a horizontal line mid-way through the V3.33 plots, that
represents roughly +/- 2.5 dB from 20 Hz through 3.5 kHz. Not too shabby
for a
communications receiver.

As a further experiment, I just added 3 dB to Rx bands 1-3 and the response
is now essentially +/- 0dB between 20Hz and 3.5 kHz in SSB through the 6K
filter and Fc = 1.35. You can lay the ruler flat on the response.

http://216.229.20.37/images/K3-V333-EQ.jpg

Paul, W9AC

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Grant Youngman

Re: K3 Audio Response - Version 3.33 Firmware

Nice!! Hard to ask for more than that :-)

Grant/NQ5T

On Sep 18, 2009, at 9:40 PM, Paul Christensen wrote:

>
> As a further experiment, I just added 3 dB to Rx bands 1-3 and the
> response
> is now essentially +/- 0dB between 20Hz and 3.5 kHz in SSB through
> the 6K
> filter and Fc = 1.35. You can lay the ruler flat on the response.
>
> http://216.229.20.37/images/K3-V333-EQ.jpg
>
> Paul, W9AC
>
> ______________________________________________________________
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DaveL G3TJP

Re: K3 Audio Response - Version 3.33 Firmware

In reply to this post by P.B. Christensen

I spent much of the evening browsing AM shortwave stations and can confirm
that the additional bass lift capability in 3.33 can be used to give a much
warmer sound. I reduced the first couple of equaliser bands to +3dB and
with the full bandwidth possible with a 13kHz filter, a slight shift below
the FC Norm of 1.5 gives much warmer audio. I did find that adjustment
varied depending on the voice being listened to in order to get the most
satisfying result. In all cases, I did not go below the 1.05 setting to
achieve the most satisfactory sound with most being around the 1.30 mark.

Similar results were heard with SSB, and brought the K3 into line with good
sound from my K2 and a comms Rx, both of which rendered a warmer audio than
the K3 prior to beta 3.33. Many thanks, Elecraft.

DaveL G3TJP

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Steve Ellington

Re: K3 Audio Response - Version 3.33 Firmware

In reply to this post by P.B. Christensen

I've just been listening all evening with a big smile on my face :*) This
is beautiful. Having the LF audio seems to make the entire spectrum sound
better. Even QRN is more pleasant to listen to. Thanks Elecraft! What took
so long? Why was bass chopped off in the first place?

Steve
N4LQ
[hidden email]
----- Original Message -----
From: "Paul Christensen" <[hidden email]>
To: <[hidden email]>
Sent: Friday, September 18, 2009 10:40 PM
Subject: [Elecraft] K3 Audio Response - Version 3.33 Firmware

>I have attached links to three .JPG images of the K3's audio response as
> measured at
> the headphone jack with SpectraPlus FFT software. Response passband was
> normalized for both modes. SSB
> is measured through the 6K filter, and CW through the 8-pole 2.8 kHz
> filter.
> However, V3.33 SSB was taken with Fc = 1.35.
>
> It would have made more sense to capture the responses such that three SSB
> plots would overlay on one graph and three CW plots on a second, but that
> took too much time in waiting for the firmware to load between plots.
> Still, you can see radical differences between firmware versions in the
> kinks below. Rx Band-1 EQ seems operational now too :-)).
>
> http://216.229.20.37/images/K3-V325.jpg
> http://216.229.20.37/images/K3-V330.jpg
> http://216.229.20.37/images/K3-V333.jpg
>
> As you can see, CW with V3.25 has the strongest low-end response relative
> to
> 1 kHz, but that can be compensated for with the first two EQ bands. Even
> as
> it is, if you draw a horizontal line mid-way through the V3.33 plots, that
> represents roughly +/- 2.5 dB from 20 Hz through 3.5 kHz. Not too shabby
> for a
> communications receiver.
>
> As a further experiment, I just added 3 dB to Rx bands 1-3 and the
> response
> is now essentially +/- 0dB between 20Hz and 3.5 kHz in SSB through the 6K
> filter and Fc = 1.35. You can lay the ruler flat on the response.
>
> http://216.229.20.37/images/K3-V333-EQ.jpg
>
> Paul, W9AC
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

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drewko

Re: K3 Audio Response - Version 3.33 Firmware

It sounds very nice on CW (and AM), even with my cheap headphones,
which are not particularly bass responsive. It is a very pleasant
extra dimension when tuning CW bands with wide open filter. It adds a
lot to the sound. I wouldn't want to go back to the narrower sound.

You can however hear a good bit more of a signal's opposite sideband
when you tune through it with a wide filter and/or Shift set very
low-- a couple hundred Hz or more on the opposite side for strong
signals. I don't think that is a problem but some may complain.

73,
Drew
AF2Z

On Sat, 19 Sep 2009 00:19:24 -0400, Steve N4LQ wrote:

>I've just been listening all evening with a big smile on my face :*) This
>is beautiful. Having the LF audio seems to make the entire spectrum sound
>better. Even QRN is more pleasant to listen to. Thanks Elecraft! What took
>so long? Why was bass chopped off in the first place?
>
>Steve
>N4LQ

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Don Wilhelm-4

Re: K3 Audio Response - Version 3.33 Firmware

Drew,

Hearing a bit of the opposite sideband is a natural effect of using a
very low Shift/Lo-Cut setting. No matter how straight sided the DSP
filter may be, it does have a finite slope to it (if it did not have
slope, it would ring like crazy).

IMHO it is not a problem either -
The cure for that condition is easily available to the operator, just
set the low end a bit higher and the opposite sideband response goes
away. If one really wants to hear those very low frequencies, he will
have to accept that a bit of opposite sideband will also be heard.

73,
Don W3FPR

drewko wrote:

> It sounds very nice on CW (and AM), even with my cheap headphones,
> which are not particularly bass responsive. It is a very pleasant
> extra dimension when tuning CW bands with wide open filter. It adds a
> lot to the sound. I wouldn't want to go back to the narrower sound.
>
> You can however hear a good bit more of a signal's opposite sideband
> when you tune through it with a wide filter and/or Shift set very
> low-- a couple hundred Hz or more on the opposite side for strong
> signals. I don't think that is a problem but some may complain.
>
>

Joe Subich, W4TV-4

Re: K3 Audio Response - Version 3.33 Firmware

> Hearing a bit of the opposite sideband is a natural effect of using a
> very low Shift/Lo-Cut setting. No matter how straight sided the DSP
> filter may be, it does have a finite slope to it (if it did not have
> slope, it would ring like crazy).

The DSP effect would be at audio. The "opposite sideband" effect
is due to no longer "fixing" the corner of the roofing filter 200
Hz away from the carrier point. Remember, audio frequencies are
imaged (folded) around the carrier.

The DSP works the same whether audio at 200 Hz is above or below
the carrier.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Don Wilhelm
> Sent: Saturday, September 19, 2009 10:30 AM
> To: drewko
> Cc: [hidden email]
> Subject: Re: [Elecraft] K3 Audio Response - Version 3.33 Firmware
>
>
> Drew,
>
> Hearing a bit of the opposite sideband is a natural effect of using a
> very low Shift/Lo-Cut setting. No matter how straight sided the DSP
> filter may be, it does have a finite slope to it (if it did not have
> slope, it would ring like crazy).
>
> IMHO it is not a problem either -
> The cure for that condition is easily available to the operator, just
> set the low end a bit higher and the opposite sideband response goes
> away. If one really wants to hear those very low
> frequencies, he will
> have to accept that a bit of opposite sideband will also be heard.
>
> 73,
> Don W3FPR
>
> drewko wrote:
> > It sounds very nice on CW (and AM), even with my cheap headphones,
> > which are not particularly bass responsive. It is a very pleasant
> > extra dimension when tuning CW bands with wide open filter.
> It adds a
> > lot to the sound. I wouldn't want to go back to the narrower sound.
> >
> > You can however hear a good bit more of a signal's opposite
> sideband
> > when you tune through it with a wide filter and/or Shift set very
> > low-- a couple hundred Hz or more on the opposite side for strong
> > signals. I don't think that is a problem but some may complain.
> >
> >
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

Joe Subich, W4TV-4

Re: K3 Audio Response - Version 3.33 Firmware

In reply to this post by P.B. Christensen

> Just for comparison, using the DSP demod on my old vintage 96
> MP. It suppresses the opposite sideband perfectly. That is 13
> years old DSP technology and firmware.

You must have an exceptional MP ... my MK V would certainly
exhibit "opposite sideband" response in CW if I moved the
PBT very low in frequency and then tuned to the other side
of the carrier. I can't think of a single radio that had
unconditional single signal response if the PBT (or filters)
were adjusted so they provided a response on the "image."

73,

... Joe, W4TV

> -----Original Message-----
> From: Arie Kleingeld PA3A [mailto:[hidden email]]
> Sent: Saturday, September 19, 2009 6:31 PM
> To: [hidden email]
> Subject: RE: [Elecraft] K3 Audio Response - Version 3.33 Firmware
>
>
> Joe,
>
> With DSP demodulation the opposite sideband suppression
> should not be a problem.
>
> Just for comparison, using the DSP demod on my old vintage 96
> MP. It suppresses the opposite sideband perfectly. That is 13
> years old DSP technology and firmware.
>
> No reason why a K3 could not match that. But it does not.
>
>
> 73
> Arie PA3A
>
> -----Oorspronkelijk bericht-----
> Van: [hidden email]
> [mailto:[hidden email]] Namens Joe Subich, W4TV
> Verzonden: zaterdag 19 september 2009 17:06
> Aan: [hidden email]
> CC: [hidden email]
> Onderwerp: Re: [Elecraft] K3 Audio Response - Version 3.33 Firmware
>
>
>
>
> > Hearing a bit of the opposite sideband is a natural effect
> of using a
> > very low Shift/Lo-Cut setting. No matter how straight
> sided the DSP
> > filter may be, it does have a finite slope to it (if it did
> not have
> > slope, it would ring like crazy).
>
> The DSP effect would be at audio. The "opposite sideband" effect
> is due to no longer "fixing" the corner of the roofing filter 200
> Hz away from the carrier point. Remember, audio frequencies are
> imaged (folded) around the carrier.
>
> The DSP works the same whether audio at 200 Hz is above or below
> the carrier.
>
> 73,
>
> ... Joe, W4TV
>
>

Arie Kleingeld PA3A-2

Re: K3 Audio Response - Version 3.33 Firmware

Joe,

The old MP dsp demod is a bit different from the MKV, as far as I know.

Given the MP.
If I shift the IF in the MP to the opposite sideband, retune with the
dial, then the signal is there just like it would be on the right
sideband. Then tap the DSP demod and 'presto' : the signal is inaudible.
(The S-meter still moves but that is because the dsp demod is outside
the AGC-loop).

Maybe the difference in suppression level is in the AGC since the MP
still has reduced gain when you tap the dsp demod, which is different
from the K3 of course.

It just struck me that the sidebandsuppression was not so absolute in
the K3. Sideband suppression is, I think, another algorithm than
passband filtering. But I'm not an expert in DSP SW.

73
Arie

-----Oorspronkelijk bericht-----

> Just for comparison, using the DSP demod on my old vintage 96
> MP. It suppresses the opposite sideband perfectly. That is 13
> years old DSP technology and firmware.

You must have an exceptional MP ... my MK V would certainly
exhibit "opposite sideband" response in CW if I moved the
PBT very low in frequency and then tuned to the other side
of the carrier. I can't think of a single radio that had
unconditional single signal response if the PBT (or filters)
were adjusted so they provided a response on the "image."

73,

... Joe, W4TV

Brett Howard

Re: K3 Audio Response - Version 3.33 Firmware

So I think I may have found a strange bug. Please someone tell me if
you can reproduce it.

With the latest 3.33 pre-released test I am unable to set the top two
knobs to HI/LOW adjustments. However this problem is only present when
the radio is in the CW mode. When in this mode tapping the HI/BW knob
doesn't change it between modes.

~Brett (KC7OTG)

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drewko

Re: K3 Audio Response - Version 3.33 Firmware

It's ok on mine , Brett: Shift/Lo and Hi/Width both work fine in CW.
Does I/II work (i.e., long push on Hi/Width)? You may have a problem
with the switch. Have you tried SW Test in the Config menu?

73,
Drew
AF2Z

On Sun, 20 Sep 2009 02:32:09 -0700, Brett (KC7OTG) wrote:

>So I think I may have found a strange bug. Please someone tell me if
>you can reproduce it.
>
>With the latest 3.33 pre-released test I am unable to set the top two
>knobs to HI/LOW adjustments. However this problem is only present when
>the radio is in the CW mode. When in this mode tapping the HI/BW knob
>doesn't change it between modes.
>
>~Brett (KC7OTG)
>

KK7P

Re: K3 Audio Response - Version 3.33 Firmware

In reply to this post by Brett Howard

> With the latest 3.33 pre-released test I am unable to set the top two
> knobs to HI/LOW adjustments. However this problem is only present when
> the radio is in the CW mode. When in this mode tapping the HI/BW knob
> doesn't change it between modes.
>

When CONFIG PB CTRL CHIFT=.01 you can;t use HI CUT/LO CUT> IF SHIFT=.05
(default), then you can. See Release notes for 3.25/2.21.

73,

Lyle KK7P

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Brett Howard

Re: K3 Audio Response - Version 3.33 Firmware

Ah yes it does look like that is the case. Went back and read it and it
clearly states (there are some limitations at present). Thats somewhat
of an esoteric one... Wonder if at some point it can be supported.
Seems like it was a difficult one to figure out at the time so rather
than dig into that section of and update it to support the new shift it
was just disabled. Its been fun watching this thing grow...

~BTH

On Sun, 2009-09-20 at 06:07 -0700, Lyle Johnson wrote:

> > With the latest 3.33 pre-released test I am unable to set the top two
> > knobs to HI/LOW adjustments. However this problem is only present when
> > the radio is in the CW mode. When in this mode tapping the HI/BW knob
> > doesn't change it between modes.
> >
>
> When CONFIG PB CTRL CHIFT=.01 you can;t use HI CUT/LO CUT> IF SHIFT=.05
> (default), then you can. See Release notes for 3.25/2.21.
>
> 73,
>
> Lyle KK7P
>

AD4C2009

Re: K3 Audio Response - Version 3.33 Firmware

In reply to this post by Brett Howard

If there is a bug it is only on your K3 because I have been using the newest FW 3.33 for 2 days now and either on CW or SSB when I tap at the LO-HI knobs they do work as always has done.

AD4C

"The difference between genius and stupidity is that genius has its limits". -- Albert Einstein

--- On Sun, 9/20/09, Brett Howard <[hidden email]> wrote:

From: Brett Howard <[hidden email]>
Subject: Re: [Elecraft] K3 Audio Response - Version 3.33 Firmware
To: [hidden email]
Cc: "Wayne Burdick - N6KR, Elecraft" <[hidden email]>
Date: Sunday, September 20, 2009, 9:32 AM

So I think I may have found a strange bug. Please someone tell me if
you can reproduce it.

With the latest 3.33 pre-released test I am unable to set the top two
knobs to HI/LOW adjustments. However this problem is only present when
the radio is in the CW mode. When in this mode tapping the HI/BW knob
doesn't change it between modes.

~Brett (KC7OTG)

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Vic K2VCO

Re: K3 Audio Response - Version 3.33 Firmware

In reply to this post by Brett Howard

I see this as a feature, not a bug. HI/LO has no utility for me in CW, and it's annoying
when I accidentally tap the DSP controls and select it. When PB CTRL is set to 0.01 --
which I like -- then the control functions are fixed as SHIFT/WIDTH in CW and HI/LO in
SSB, exactly what I want.

In this case, tapping the knobs displays their settings without changing anything.

Please do not 'fix' this!

Brett Howard wrote:

> Ah yes it does look like that is the case. Went back and read it and it
> clearly states (there are some limitations at present). Thats somewhat
> of an esoteric one... Wonder if at some point it can be supported.
> Seems like it was a difficult one to figure out at the time so rather
> than dig into that section of and update it to support the new shift it
> was just disabled. Its been fun watching this thing grow...
>
> ~BTH
>
> On Sun, 2009-09-20 at 06:07 -0700, Lyle Johnson wrote:
>>> With the latest 3.33 pre-released test I am unable to set the top two
>>> knobs to HI/LOW adjustments. However this problem is only present when
>>> the radio is in the CW mode. When in this mode tapping the HI/BW knob
>>> doesn't change it between modes.
>>>
>> When CONFIG PB CTRL CHIFT=.01 you can;t use HI CUT/LO CUT> IF SHIFT=.05
>> (default), then you can. See Release notes for 3.25/2.21.
>>
>> 73,
>>
>> Lyle KK7P

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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Ignacy

Re: K3 Audio Response - Version 3.33 Firmware

In reply to this post by P.B. Christensen

Is this measured with high impedance probes? If I remember correctly, small caps limit low-frequency response of K3 especially with low impedance phones/speakers.
Ignacy

As a further experiment, I just added 3 dB to Rx bands 1-3 and the response
is now essentially +/- 0dB between 20Hz and 3.5 kHz in SSB through the 6K
filter and Fc = 1.35. You can lay the ruler flat on the response.

http://216.229.20.37/images/K3-V333-EQ.jpg

Paul, W9AC

___

P.B. Christensen

Re: K3 Audio Response - Version 3.33 Firmware

> Is this measured with high impedance probes? If I remember correctly,
> small
> caps limit low-frequency response of K3 especially with low impedance
> phones/speakers.
> Ignacy

Correct, measured with a 2K-ohm load resistance at the sound card input.
The purpose of the test was to measure only the response plots as a result
of changes in DSP versions. To get a ruler-flat response down to 20 Hz with
headphones may require a change in C9/C13 on the Main DSP Board, depending
on the Z of your headphones at that frequency. I changed C9/C13 with 330uF
units and this work well with any commercial headphones.

If you refer to the K3's schematic, note that 8-ohm series build-out
resistors are used and appear "off-page." The addition of the build-out
resistors has the effect of improving low-end response as the headphone Z
decreases.

As a practical matter, and assuming one is using newer headphones with a Z
of at least 30 ohms at roughly 50 Hz, then Elecraft's revised Main DSP Board
with 100uF caps at C9/C13 are completely sufficient.

More info here: http://www.n1eu.com/K3/k3audiomod.htm

W9AC

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Brett Howard

Re: K3 Audio Response - Version 3.33 Firmware

In reply to this post by Ignacy

Yes but unless the response remains that way when an 8 ohm speaker is
there its not a very useful measurement.

~BTH

On Sun, 2009-09-20 at 07:56 -0700, Ignacy wrote:

> Is this measured with high impedance probes? If I remember correctly, small
> caps limit low-frequency response of K3 especially with low impedance
> phones/speakers.
> Ignacy
>
>
> As a further experiment, I just added 3 dB to Rx bands 1-3 and the response
> is now essentially +/- 0dB between 20Hz and 3.5 kHz in SSB through the 6K
> filter and Fc = 1.35. You can lay the ruler flat on the response.
>
> http://216.229.20.37/images/K3-V333-EQ.jpg
>
> Paul, W9AC
>
> ___

Joe Subich, W4TV-4

Re: K3 Audio Response - Version 3.33 Firmware

> Yes but unless the response remains that way when an 8 ohm
> speaker is there its not a very useful measurement.

Since the speaker coupling capacitors are 470 uF, the roll off
at 100 Hz with 8 Ohm speakers is 3 dB. That's completely
acceptable for a communications receiver ... and probably less
LF roll off than you will observe due to the speaker enclosure.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Brett Howard
> Sent: Sunday, September 20, 2009 7:42 PM
> To: Ignacy
> Cc: [hidden email]
> Subject: Re: [Elecraft] [K3] K3 Audio Response - Version 3.33 Firmware
>
>
> Yes but unless the response remains that way when an 8 ohm
> speaker is there its not a very useful measurement.
>
> ~BTH
>
> On Sun, 2009-09-20 at 07:56 -0700, Ignacy wrote:
> > Is this measured with high impedance probes? If I remember
> correctly,
> > small caps limit low-frequency response of K3 especially with low
> > impedance phones/speakers. Ignacy
> >
> >
> > As a further experiment, I just added 3 dB to Rx bands 1-3 and the
> > response is now essentially +/- 0dB between 20Hz and 3.5 kHz in SSB
> > through the 6K filter and Fc = 1.35. You can lay the ruler flat on
> > the response.
> >
> > http://216.229.20.37/images/K3-V333-EQ.jpg
> >
> > Paul, W9AC
> >
> > ___
>
>
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Brett Howard

Re: K3 Audio Response - Version 3.33 Firmware

This is true. I actually messed with my EQ settings using an RTA and a
calibrated microphone measuring the full system including my speakers
and the amplifier.

~BTH

On Sun, 2009-09-20 at 20:27 -0400, Joe Subich, W4TV wrote:

>
> > Yes but unless the response remains that way when an 8 ohm
> > speaker is there its not a very useful measurement.
>
> Since the speaker coupling capacitors are 470 uF, the roll off
> at 100 Hz with 8 Ohm speakers is 3 dB. That's completely
> acceptable for a communications receiver ... and probably less
> LF roll off than you will observe due to the speaker enclosure.
>
> 73,
>
> ... Joe, W4TV
>
>
>
> > -----Original Message-----
> > From: [hidden email]
> > [mailto:[hidden email]] On Behalf Of Brett Howard
> > Sent: Sunday, September 20, 2009 7:42 PM
> > To: Ignacy
> > Cc: [hidden email]
> > Subject: Re: [Elecraft] [K3] K3 Audio Response - Version 3.33 Firmware
> >
> >
> > Yes but unless the response remains that way when an 8 ohm
> > speaker is there its not a very useful measurement.
> >
> > ~BTH
> >
> > On Sun, 2009-09-20 at 07:56 -0700, Ignacy wrote:
> > > Is this measured with high impedance probes? If I remember
> > correctly,
> > > small caps limit low-frequency response of K3 especially with low
> > > impedance phones/speakers. Ignacy
> > >
> > >
> > > As a further experiment, I just added 3 dB to Rx bands 1-3 and the
> > > response is now essentially +/- 0dB between 20Hz and 3.5 kHz in SSB
> > > through the 6K filter and Fc = 1.35. You can lay the ruler flat on
> > > the response.
> > >
> > > http://216.229.20.37/images/K3-V333-EQ.jpg
> > >
> > > Paul, W9AC
> > >
> > > ___
> >
> >
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
>