K3 Rev C DSP with Low Freq Enhancement ship date info; New swap out option on parts order page.

[Eric Swartz - WA6HHQ]

We started shipping the current DSP boards, Rev C, approximately March
6th, 2009.
Any K3 DSP board Rev C or later will have the extended low end audio
frequency response h/w enhancement.

This corresponds approximately to K3 serial number 2800, plus or minus
10-20. Since assembled -Fs and kit K3s flow through different
manufacturing paths, there is a slight variance in s/n for the phase-in.
If in doubt, check the DSP board Rev as noted above.

These changes basically added additional h/w low end frequency response
below 300 Hz. You need to also have the latest K3 f/w to take advantage
of this. Of course, you can also tailor (and limit) your RX and TX
response via the K3's IF Shift and B/W controls and by using the TX and
RX Equalizer entries.

A picture of the Rev label location on the DSP board and additional info
is at:
http://www.elecraft.com/K3/mods/dsp_rev_c_information.htm

(The 'C', or later, revision letter at the bottom of the label is what
is important.)

We have added to our parts and mod kits page an option, K3DSPUPGD to
swap out your current DSP for one upgraded to the latest Rev C changes.
The cost will be $69.00 plus shipping. Order placed via this page will
start shipping approximately in 4 weeks, around Nov 9.

See:
http://www.elecraft.com/order_form_parts.htm#K3%20Parts


73,  Eric   WA6HHQ
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[Eric Swartz - WA6HHQ]

CORRECTION - I have some egg on my face. I misread our internal release
date notes for the Rev C DSP board. Here is the correct Date and S/N
Information:

We started shipping the latest DSP boards, Rev C, approximately May 1st,
2009.
Any K3 DSP board Rev C or later will have the extended low end audio
response enhancement.

This corresponds approximately to K3 serial number 3018, plus or minus
10-20.

The complete upgrade info page has also been updated with this information:

http://www.elecraft.com/K3/mods/dsp_rev_c_information.htm

I apologize for any confusion this created.

73, Eric
----
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[Geoffrey Downs-2]

Thanks for the clarification, Eric. For those with a sub rx, if a pre-Rev C
main dsp board is swapped does the Aux DSP board need to be changed too?

73

Geoff
G3UCK

----- Original Message -----
From: "Eric Swartz - WA6HHQ, Elecraft" <[hidden email]>


> We started shipping the latest DSP boards, Rev C, approximately May 1st,
> 2009.
> Any K3 DSP board Rev C or later will have the extended low end audio
> response enhancement.

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[akiwi ham]

I am confused about the Rev C DSP board.
Is there more to it than the extended low end audio frequency response
h/w enhancement?
If so can someone point me to where I can see more information please?

Bryan, Zl1NI


Eric wrote:
..............................................
> Any K3 DSP board Rev C or later will have the extended low end audio

> frequency response h/w enhancement.
>
..............................................

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[Eric Swartz - WA6HHQ]

No. All the analog audio paths impacted are only on the main DSP board.
The AUXDSP is all digital.

73, Eric


Geoffrey Downs wrote:

> Thanks for the clarification, Eric. For those with a sub rx, if a
> pre-Rev C main dsp board is swapped does the Aux DSP board need to be
> changed too?
>
> 73
>
> Geoff
> G3UCK
>
> ----- Original Message ----- From: "Eric Swartz - WA6HHQ, Elecraft"
> <[hidden email]>
>
>
>> We started shipping the latest DSP boards, Rev C, approximately May 1st,
>> 2009.
>> Any K3 DSP board Rev C or later will have the extended low end audio
>> response enhancement.

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[Eric Swartz - WA6HHQ]

That's primarily it. We increased coupling caps and a few other values
in the audio chain to increase low freq audio response below 300 Hz.
when combines with the latest f/w beta release it results in more low
end below 300 Hz.  Its not something we originally targeted as a
communications radio, but as our customer base has widened its become a
desire enhancement for those who like both hi-fi SWLing, ESSB and some
other areas.

73, Eric  WA6HHQ
----

Bryan, ZL1NI wrote:
> I am confused about the Rev C DSP board.
> Is there more to it than the extended low end audio frequency response
> h/w enhancement?
> If so can someone point me to where I can see more information please?
>
> Bryan, Zl1NI
>
>  
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[Craig K3OOL]

Is the hardware mod to the DSP board required to see any effect from the f/w change in
3.41?

<quote author="Eric Swartz - WA6HHQ, Elecraft">
That's primarily it. We increased coupling caps and a few other values
in the audio chain to increase low freq audio response below 300 Hz.
when combines with the latest f/w beta release it results in more low
end below 300 Hz.  ....

[KK7P]

> Is the hardware mod to the DSP board required to see any effect from the f/w
> change in 3.41?

No.

The hardware mods improve the *TX* audio path low frequency response from all
three sources (front microphone, rear microphone, line in).  They also improve
the Rx low frequency response for *headphones* only.  Lined out and speaker
low frequency responses are not affected.

73,

Lyle KK7P/7 (in Tucson, AZ)



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[Brett Howard]

On Fri, 2009-10-09 at 13:37 -0700, Craig K3OOL wrote:
> Is the hardware mod to the DSP board required to see any effect from the f/w
> change in
> 3.41?
>
>
> That's primarily it. We increased coupling caps and a few other values
> in the audio chain to increase low freq audio response below 300 Hz.
> when combines with the latest f/w beta release it results in more low
> end below 300 Hz.  ....

I really wish we could get a full listing of the modifications that
Elecraft is officially rolling into this DSP board revision.  It doesn't
even have to come with rework instructions and pictures...  Just a list
of value changes would have me pleased as punch.

~BTH

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[Bill W4ZV]

Brett Howard wrote

I really wish we could get a full listing of the modifications that
Elecraft is officially rolling into this DSP board revision.  It doesn't
even have to come with rework instructions and pictures...  Just a list
of value changes would have me pleased as punch.

This should be close but Elecraft has not updated their schematics since October 2008, so there could be differences:

http://n1eu.com/K3/k3audiomod.htm

73,  Bill

[P.B. Christensen]

> This should be close but Elecraft has not updated their schematics since
> October 2008, so there could be differences:
>
> http://n1eu.com/K3/k3audiomod.htm

Lyle and I exchanged notes on this a while back as he and I were
experimenting with DSP Board component changes above and beyond the
much-discussed headphone cap change.  My guess is that the Rev. C board
changes take the notes in the link into account.  However, he was re-scaling
R values.  I had re-scaled C values since fewer components were involved in
solder re-work.  The net result is essentially the same but changing R
values likely makes more sense in production where the cost of SMT resistors
is essentially the same irrespective of component value versus the increased
cost of higher-valued capacitors.  And as Bill points out, there may be
other subtle differences.

Given the number of changes to the DSP Board, I recommend taking advantage
of Elecraft's swap-out program unless there's a lot of comfort in SMT/SMD
re-work.

Paul, W9AC

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[Brett Howard]

I have a lot of confidence in SMT rework and I've done the C9 and C13
mod with exact replacement caps.  I was told that changing those to
100uF was an official Elecraft mod so I went out and found the exact
size replacement SMT caps and got them on there.  They look like they
were installed from the factory.  I've got all the equipment to do SMT
rework right down to removal and replacement of BGA components.  If I
just had an official list of modifications I'd just do it.

Wonder if the replacement DSP board requires the return of our current
one.  My current one has traces cut for the low pass audio filter and
what not...

~Brett

On Sat, 2009-10-10 at 07:37 -0400, Paul Christensen wrote:

> > This should be close but Elecraft has not updated their schematics since
> > October 2008, so there could be differences:
> >
> > http://n1eu.com/K3/k3audiomod.htm
>
> Lyle and I exchanged notes on this a while back as he and I were
> experimenting with DSP Board component changes above and beyond the
> much-discussed headphone cap change.  My guess is that the Rev. C board
> changes take the notes in the link into account.  However, he was re-scaling
> R values.  I had re-scaled C values since fewer components were involved in
> solder re-work.  The net result is essentially the same but changing R
> values likely makes more sense in production where the cost of SMT resistors
> is essentially the same irrespective of component value versus the increased
> cost of higher-valued capacitors.  And as Bill points out, there may be
> other subtle differences.
>
> Given the number of changes to the DSP Board, I recommend taking advantage
> of Elecraft's swap-out program unless there's a lot of comfort in SMT/SMD
> re-work.
>
> Paul, W9AC
>
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[DaveL G3TJP]

May I ask why the LF response improvement was confined to headphones only?

Why was the improvement not applied to all audio outputs, or am I missing something here?

Grateful thanks.  DaveL  G3TJP

Lyle Johnson wrote:
The hardware mods improve the *TX* audio path low frequency response from all
three sources (front microphone, rear microphone, line in).  They also improve
the Rx low frequency response for *headphones* only.  Lined out and speaker
low frequency responses are not affected.
73,
Lyle KK7P/7 (in Tucson, AZ)
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[KK7P]

> May I ask why the LF response improvement was confined to headphones only?

The speaker system has its own amplifier and already has excellent low
frequency response.

The headphones have their own amplifier and had 10 uF output caps, now changed
to 100 uF.

Line out also has its own amplifier and output network.

Note that these are the electrical paths.  The firmware LF improvement applies
to *all* paths: headphones, speakers and line out.

73,

Lyle KK7P/7 (Tucson AZ)
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[Julian, G4ILO]

KK7P wrote

> May I ask why the LF response improvement was confined to headphones only?

The speaker system has its own amplifier and already has excellent low
frequency response.

The headphones have their own amplifier and had 10 uF output caps, now changed
to 100 uF.

Line out also has its own amplifier and output network.

Note that these are the electrical paths.  The firmware LF improvement applies
to *all* paths: headphones, speakers and line out.

Is there any difference between the official modifications and this one: http://ur5lam.jimdo.com/elecraft-k3-mod-s-page/ ? I find it a bit difficult to see exactly what the unofficial mods are as it isn't entirely clear what components / boards are affected from the photographs. I can't really justify the cost of replacing the DSP board given that I don't think there is much wrong with the K3 audio at the moment. But I have a big bag of assorted electrolytic capacitors sitting in my junk box.

[P.B. Christensen]

> Why was the improvement not applied to all audio outputs, or am I missing
> something here?

When you go through the schematic and run the response calculations, those
were the only changes necessary to improve low-end response for all Rx and
Tx paths.

Take a look at what's happening before the ADC and after the DAC circuits.
The K3 has some of the best designed audio circuits for a communications
transceiver.

Paul, W9AC

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[Steve Ellington]

Paul
This is so confusing. First, a hardware change (2 caps) improves bass then
along comes a firmware change that does the same thing but only for
headphones and line out and then a new DSP board that works with the
firmware to do the same thing but still only for headphones and line out and
now we're back to the 2 caps that improve headphone, line and speaker audio.
No wonder there are so many questions. I wish someone would make this more
clear.
Steve
N4LQ
[hidden email]
----- Original Message -----
From: "Paul Christensen" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, October 10, 2009 7:54 PM
Subject: Re: [Elecraft] [K3] K3 Rev C DSP with Low Freq Enhancement
shipdateinfo; New swap out option on parts order page. CORRECTION

>> Why was the improvement not applied to all audio outputs, or am I missing
>> something here?
>
> When you go through the schematic and run the response calculations, those
> were the only changes necessary to improve low-end response for all Rx and
> Tx paths.
>
> Take a look at what's happening before the ADC and after the DAC circuits.
> The K3 has some of the best designed audio circuits for a communications
> transceiver.
>
> Paul, W9AC
>
> ______________________________________________________________
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> Please help support this email list: http://www.qsl.net/donate.html 

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[Don Wilhelm-4]

Steve,

Hopefully I can make it more clear.

The speaker and line out audio *already* had sufficient low response
with no changes.  The headphone output had limitations unless higher
impedance headphones were used.  The capacitor changes allowed lower
frequency response with lower impedance headphones.

As for the firmware, previously, the bass response was limited in the
firmware.  That limitation has now been relaxed and greater low
frequency content can be heard in the speaker (assuming you have a
speaker that can produce those lows, the internal speaker is not that
speaker), or at line out.  If you are using low impedance headphones,
you will need to increase the capacitors to hear the difference in the
headphone output.

73,
Don W3FPR

Steve Ellington wrote:

> Paul
> This is so confusing. First, a hardware change (2 caps) improves bass then
> along comes a firmware change that does the same thing but only for
> headphones and line out and then a new DSP board that works with the
> firmware to do the same thing but still only for headphones and line out and
> now we're back to the 2 caps that improve headphone, line and speaker audio.
> No wonder there are so many questions. I wish someone would make this more
> clear.
> Steve
> N4LQ
> [hidden email]
>  
>

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[KK7P]

Let me try and eliminate the confusion.

1) The low frequency response is constrained by two things: the audio path
components, and the various filters (roofing filter, DSP IF filter and DSP
audio filter (including Rx Equalizer).

2) Several months ago, there were circuit component changes made to the DSP
board to improve Tx and Rx low frequency response.  The Rx path that was
changed was the headphone path -- 10 yF output capacitors were changed to 100
uF capacitors.  There was no need to change components in the speaker or Line
Out circuitry.

3) At the time these capacitors were changed, *other* component changes were
made to improve the *transmit* audio low frequency response.  Several
components were changed to improve this response for the front panel
microphone, rear panel microphone, and line input paths.

4) With these changes, the receive low frequency response was now limited by
the various filters (roofing filter, DSP IF filter and DSP audio filter).

5) The firmware in the K3 sets up the filters for maximum "communications"
effectiveness, making the nominal low frequency roll-off around 200 Hz.

6) The latest beta test firmware *allows* you to move the combined *filter*
response lower, improving low frequency fidelity if you so desire.  This will
affect all the possible receive paths: speaker, headphones and line out.

73,

Lyle KK7P/7 (vacationing in Tucson AZ)
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[P.B. Christensen]

> 3) At the time these capacitors were changed, *other* component changes
> were
> made to improve the *transmit* audio low frequency response.  Several
> components were changed to improve this response for the front panel
> microphone, rear panel microphone, and line input paths.

Lyle,

As I recall, the *other* changes affect both line-in and mic-in.  On the
N1EU website, I've documented those changes with only C value changes
instead of R value changes.

I think what some folks are requesting is an updated schematic, showing the
new values.  But what they may not realize is that 7 SMT capacitors are
changed -- or in the alternative, the corresponding SMT resistors require
solder re-work and that's in addition to the C9/C13 change and so the total
parts change may be in excess of 10.  That's a lot of propensity for damage
to the board and it really makes sense to just opt for the board swap
through Elecraft.

Paul, W9AC

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