Re: K3 Audio our artifacts

[Dave Hachadorian]

I would guess that the headphone output is expecting a low Z
(~16 ohm?) termination, and your sound card has a high Z in.
Try a terminating resistor across the headphone jack in
parallel with your sound card.

Just a guess.

Dave Hachadorian, K6LL
Yuma, AZ

----- Original Message -----
From: "Mike Scott" <[hidden email]>
To: <[hidden email]>
Sent: Monday, March 02, 2009 5:36 PM
Subject: [Elecraft] K3 Audio out artifacts

>I have been investigating audio artifacts in connection
>with the K3 AGC hold
> experimental firmware. As a reminder, I live in a high
> noise area.
>
> As part of the investigation I have been looking at both
> Line Out and
> headphone audio using Spectrumlab on my PC.
>
> I am finding substantial 60-hz contamination on headphone
> audio that I do
> not see on Line Out.
>
> On Line Out I see what looks like fairly clean audio with
> donor lines at
> 2400 Hz and 3600 Hz outside the rx filter pass band (1 KHz
> DSP filtering). I
> presume these are the 40th and 60th harmonics of 60 Hz.
> They are 50 dB below
> noise background noise.
>
> With only a change of where I plug the PC audio cable
> (moving from Line Out
> jack to rear headphone jack) the audio looks quite
> different.
>
> Now I see a whole array of 60 Hz artifacts. The 3rd and
> 5th harmonics are
> about equal to comfortable listening level audio.  As I
> look higher in
> frequency the harmonics generally reduce in level but only
> to about 20 dB
> below comfortable audio listening level. There is also a
> broad artifact (300
> Hz wide) at roughly 3300 Hz that is also 25 dB down.
>
> The artifacts do not go away with reduced volume control
> settings but remain
> a constant feature of headphone audio out at any setting.
>
> Is there something about my test set up that I do not
> understand?
> Does anybody else see contamination of headphone audio on
> their K3?
> Could there be something wrong with my K3?
> Could transformer coupling (Line Out) vs direct coupling
> (headphone) be
> adding something to my test set up that I am not factoring
> into the problem?
>
>
> I have never quite believed the audio of my K3 was like
> Wayne says it should
> be but can make it better using slow AGC (separate post),
> I doubt that has
> anything to do with the artifacts I see here.
>
>
> Mike Scott - AE6WA
> Tarzana, CA (DM04 / near LA)
> NAQCC 3535
> K3-100 #508 / KX1  #1311
>

[

______________________________________________________________
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

[Jim Brown-10]

On Mon, 2 Mar 2009 18:23:57 -0000, Dave Hachadorian wrote:

> would guess that the headphone output is expecting a low Z
>(~16 ohm?) termination, and your sound card has a high Z in.
>Try a terminating resistor across the headphone jack in
>parallel with your sound card.

No, termination has nothing to do with it. It's either power line
hum/buzz or 60Hz leakage flux from a power transformer.

73,

Jim K9YC


______________________________________________________________
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

[Jim Brown-10]

On Mon, 02 Mar 2009 18:58:58 +0000, Brian Alsop wrote:

>I'm wondering about a UPS supply that's attached to the computer.   Do
>they only kick in when power goes out

That is nearly always how they work. BUT -- if the transformer is
energized, there will be a field. So it depends on how that particular
device works.

>Have the opposite problem with earphones clean but line out polluted by
>third and other odd harmonics.

That's produced in the line out transformer because there's 600 ohms in
series with it and the output driver. The mod fixes that by reducing the
resistors to a much smaller value (50 ohms, I think).

73,

Jim Brown K9YC


______________________________________________________________
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

[David Woolley (E.L)]

Jim Brown wrote:
> On Mon, 02 Mar 2009 18:58:58 +0000, Brian Alsop wrote:
>
>> I'm wondering about a UPS supply that's attached to the computer.   Do
>> they only kick in when power goes out
>
> That is nearly always how they work. BUT -- if the transformer is

The sort of UPS that would be used by a data centre would normally
always use the inverter, the argument being that it avoids mains
transients (and, presumably, gives a cleaner switch over).


--
David Woolley
"The Elecraft list is a forum for the discussion of topics related to
Elecraft products and more general topics related ham radio"
List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm>
______________________________________________________________
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

[ac0h]

David is correct.

You really need to look hard to find an inverter type of UPS in the
consumer market. All of the consumer grade UPS's I know about (APC,
Tripp-lite, etc....) are switching types and have been known to cause
problems.


David Woolley (E.L) wrote:

> Jim Brown wrote:
>> On Mon, 02 Mar 2009 18:58:58 +0000, Brian Alsop wrote:
>>
>>> I'm wondering about a UPS supply that's attached to the computer.   Do
>>> they only kick in when power goes out
>> That is nearly always how they work. BUT -- if the transformer is
>
> The sort of UPS that would be used by a data centre would normally
> always use the inverter, the argument being that it avoids mains
> transients (and, presumably, gives a cleaner switch over).
>
>

--
R. Kevin Stover, ACØH
______________________________________________________________
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