(no subject)

[K7TV]

Joe,

 

Thanks for your comments; they fit well with my observations so far.

I may have more on the subject if I get around to testing the computer line
audio input with an external preamp for the microphone, and testing the
laptop when running on batteries etc.

 

In the meantime, here is an anecdotal indication that seems to support what
we are saying:

Unrelated to my sound recording need, I recently installed Skype on the
desktop and had one conversation through it, using the microphone input. I
didn't get any complaint about noise from the other party, probably because
we are used to audio flaws in telephone conversations. The significant part
of the experience: During the Skype setup process, advice about microphones
was given. It was said that an analog microphone is acceptable, but a "USB
microphone" is the best. Nobody is going to convince me that the microphone
in a $30 "USB microphone" is "better" than a good analog microphone, so I
think what they are saying is that having the A to D conversion external to
the computer may result in lower noise because it keeps low level microphone
analog signal outside of the motherboard.

 

Erik K7TV

 

 

Eric,

 

Sound facilities integrated on computer main boards - both "desk" and laptop
systems - are notorious for noise issues.  Mainboard designers simply do not
have the experience in keeping signal lines "clean" and doing the level of
bypassing/decoupling necessary to maintain power supplies clean enough for
audio (analog) signals.  They have gotten sloppy since the digital domain is
much more forgiving of "low level"

noise.

 

Fortunately or unfortunately depending on one's point of view, the sloppy
audio practices are a primary reason that external audio devices tend to
provide a much higher level or performance today.  That has not always been
the case and some PCI/PCI-E sound cards go to extraordinary lengths to clean
up the power supply to avoid the problems.

 

73,

 

    ... Joe, W4TV

 

 

 

On 1/9/2012 10:50 AM, Erik Basilier wrote:

> Dave, "decent quality" may be a somewhat subjective concept. Without

> the software noise reduction in the computer, the microphone

> recordings sound very good, except for that noise which is noticeable

> in pauses. With noise reduction on, the situation is reversed: Low

> noise during pauses, almost like a noise gate, but artifacts during

> words. To be more precise about the artifacts, I don't notice a great

> deal of reduction in higher audio frequencies as has sometimes been

> observed in radios' noise reduction algorithms, but mostly a metallic

> twang, similar to "robot speech" in an old sci-fi movie, which is most

> obvious at start of recording and at the end of words, where the

> speech signal level is close to zero. (This is all using the standard

> Sound Recorder that comes with Windows 7.)

>

>

>

> The KX3 I/Q outputs may for all I know have sufficient levels that

> they can feed the sound card's line input. That input doesn't

> necessarily have the same noise problem as does the microphone input;

> I have never tried the line input on this rather new PC. To clarify,

> when I referred to past digital mode usage, it was not on this

> computer but on either an older desktop or on the old laptop. As I

> recall from the small number of qso's using the laptop, the results

> may have been inferior on receive compared to the old desktop, which had a
mid-level brand name PCI soundcard.

>

>

>

> I don't think it fair to expect Elecraft to somehow guarantee that a

> user who wants to make use of the KX3 I/Q outputs will get optimal

> results with all computers' sound cards. For starters, most laptops

> obviously won't do the job without an external soundcard, since they don't
have stereo inputs.

> I would expect that a good internal sound card will do a better job

> than most motherboard-integrated "sound cards", and that a good

> external one will perform best, even if one doesn't need a high

> sampling frequency for a given application.

>

>

>

> I would not assume that the noise performance of the microphone input

> is determined by the quality of the sound chip, but that the layout of

> the card, as well as decoupling and isolation components play a

> significant role in preventing sub-millivolt noise signals from

> entering the signal chain at some point before digitization.

>

>

>

>

>

> 73,

>

> Erik K7TV

>

 

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[Jim Brown-10]

On 1/9/2012 10:17 AM, Erik Basilier wrote:
> Nobody is going to convince me that the microphone
> in a $30 "USB microphone" is "better" than a good analog microphone,

ALL microphones are analog. It is the connection to the computer that is
digital. FWIW, many (most?) of the microphone elements that Heil sells
are super cheapie capsules (a buck or less).

My profession is pro audio, and while I don't have the experience of
seeing a broad variety of computer sound cards like Joe, W4TV, I would
generally agree with his assessment.  He's a retired broadcast engineer,
and has made it his business to know what's going on in his new
business. On the other hand, some inexpensive computer sound cards are
much better than others.  For about ten years, I've used nothing but top
line Thinkpads, which DO have decent sound cards. All that it takes is a
proper connection to them.

I would suspect a problem with the connection of the mic (or the rig) to
the computer sound card.  I've written a couple of tutorials on that
topic, which are on my website.
http://audiosystemsgroup.com/publish.htm  If you know which end of a
soldering iron to pick up it is VERY easy to make the proper
adapter(s).  The tutorials also list part numbers and sources for good
quality audio connectors.

73, Jim Brown K9YC
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