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8669Re: [BCD396XT] Audio

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  • Mark Levine, D.C.
    Dec 24 6:36 PM
    • 0 Attachment
      Wasn't there also a situation where if you shorted part of the earphone to
      ground it blew the audio amp, or was that on the 396T?

      ----- Original Message -----
      From: "lamarrsy" <lamarrsy@...>
      To: <BCD396XT@yahoogroups.com>
      Sent: Tuesday, December 24, 2013 9:11 PM
      Subject: Re: [BCD396XT] Audio


      One factor to take into account with a speaker that is overrated vs the amp
      output power used to drive it, is the *distortion* generated by this
      arrangement: this distortion creates harmonics that can be outside the
      reproducing range of the speaker.

      -Sylvain, VE2LAM, via  iPhone

      > Le 2013-12-24 à 16:32, Jeffry Rehm <scanman1958@...> a écrit :
      > I would like to add that knowing there is a high probability of a wrong
      > modulation entered then Uniden should have made absolutley sure the
      > speaker was good enough to handle that extra load. Just in case of
      > accidental entry.
      > ------------------------------
      >> On Tue, Dec 24, 2013 1:48 PM CST Ronski45 wrote:
      >> According to Uniden's manual on the 396XT, the audio output is 310 mW
      >> across a 24 ohm load. While the speaker is rated at 0.8 W, 24 ohm. So the
      >> unit's max output is 0.31 watts while the speaker should be able to
      >> handle 0.8 watts.
      >> So your saying that the other. 49 watts or some 60% will be taken up by
      >> the modulation? No, the difference in audio is quite minor, I tried it
      >> here. Yes if one runs any component at full power for a long time will
      >> further stress a component, but its the high failure rates of speakers
      >> that these speakers just arent that great in quality.
      >> Far as saying im a database guy, was just saying about having knowledge.
      >> Yes the database isnt perfect thats why we have admins to update it.
      >> Theres nothing official about it, its all user generated. If you see a
      >> problem, all be it modulation or otherwise , submit the correction is
      >> all.
      >> MCH <mch@...> wrote:
      >>> And "slightly" exceeding the spec is all it takes to blow a speaker if
      >>> you are close to the limit to star with. Of course, "Slightly" in this
      >>> case is double the voltage which is what will happen if you monitor a
      >>> FM
      >>> transmission in NFM or AUTO mode. It may not sound like much to your
      >>> ear, but it is greatly different to your speaker. And if the speaker is
      >>> rated at 5V (just picking numbers for this example), and the normal
      >>> maximum audio fed to it is 3V you will be fine, but doubling that means
      >>> you would be feeding 6V which can easily damage the speaker.
      >>> Nothing you said invalidates this technical example. I don't see what
      >>> programming knowledge or being a RR admin have to do with this. In
      >>> fact,
      >>> there are lots of incorrect entries on RR for modulation, so I guess if
      >>> it comes down to an incorrect setting, and it was DLed from RR, that
      >>> could be a contributing factor. ;-)
      >>> But, it is a fact that choosing the wrong modulation COULD result in
      >>> higher-then-spec levels to the speaker, and it is a fact that
      >>> higher-then-spec levels could blow a speaker. Just ask anyone who
      >>> connected a 100W stereo up to a 50W speaker (or even a 60W stereo).
      >>> It's
      >>> the exact same theory.
      >>> Bottom line is to program the correct modulation for the channel and
      >>> you
      >>> should be able to avoid prolonged excessive levels. This is good
      >>> engineering practice, and I would hope you would agree.
      >>> Joe M.
      >>> Ronski45 wrote:
      >>> Changing modulation will only change the volumes slightly, if your
      >>> using
      >>> the wrong modulation the audio is only going to change slightly but
      >>> not
      >>> completely cut out as was mentioned. This not a modulation issue.
      >>> See upman
      >>> http://forums.radioreference.com/uniden-scanners/144068-396t-vs-396xt-speaker.html#post1066999
      >>> "The audio level (volume) will be unbalanced. If the xmit is FM and
      >>> you
      >>> pick NFM, it will be too loud as compared to properly demodulated
      >>> signals. If it is NFM and you pick FM, it won't be loud enough."
      >>> Wrong modulation wont make the speaker stop is all Im saying.
      >>> Ive programmed about 300 radios and am a database admin at
      >>> radioreference.
      >>> Other thing is when the other faulty radios came to me they all said
      >>> the
      >>> same about static, missing audio at times before hand then nothing as
      >>> was also mentioned originally .
      >>> MCH <mch@...> wrote:
      >>> As I mentioned before - just make sure you are using the correct
      >>> mode
      >>> for the channel. It's quite possible that most of these cases
      >>> come down
      >>> to the incorrect channel settings - specifically, using AUTO or
      >>> NFM on
      >>> channels that are still using FM modulation. This results in
      >>> raising
      >>> the
      >>> audio level, and while some people endorse that since it results
      >>> in
      >>> louder audio, it might result in higher-than-spec levels going to
      >>> the
      >>> speaker and causing damage.
      >>> If in doubt, use FM and not AUTO or NFM.
      >>> Joe M.
      >>> Jm Adams wrote:
      >>>> Just hope Uniden got the issue figured out and current
      >>> production
      >>> has
      >>>> better speakers. I really like my scanner I purchased it back
      >>> in
      >>> July so
      >>>> now I'm on pins and needles hoping the speaker in my unit
      >>> doesn't
      >>> take
      >>>> a dump on me
      >>>> Sent from my iPhone
      >>>> On Dec 24, 2013, at 7:35, Ronski45 <ronski45@...
      >>>> <mailto:ronski45@...> wrote:
      >>>> This is clearly the weak point on that radio model and the
      >>> 396T.
      >>> Ive
      >>>> personally seen four, three of em being less than a week old
      >>> that the
      >>>> speaker is shot. Uniden didnt do their homework on this part
      >>> and/or
      >>>> their supplier.
      >>>> Take a look at
      >>> http://wiki.radioreference.com/index.php/Replace_a_Blown_Speaker_in_the_396
      >>>> One thing I keep wondering on that is what holds in the
      >>> speaker?
      >>>> And see all the others having the same problem -
      >>> http://www.radioreference.com/apps/Search/?cx=014732645207632841850%3Afkjydvmuoq4&q=396+speaker+replacement+&sa.x=0&sa.y=0&cof=FORID%3A9&name=Search
      >>> <http://www.radioreference.com/apps/Search/?cx=014732645207632841850%3Afkjydvmuoq4&q=396+speaker+replacement+&sa.x=0&sa.y=0&cof=FORID%3A9&name=Search>
      >>>> OB <ob1309@... <mailto:ob1309@...> wrote:
      >>>> Had that happen twice on the speaker on the original unit and
      >>> then
      >>>> the replacement one too. Third one is holding up nicely. All
      >>>> repaired under warranty by Uniden Australia (Sydney).
      >>>> OB
      >>>> On 24 Dec 2013, at 05:13, <K4ADD@...
      >>> <mailto:K4ADD@...>
      >>>> wrote:
      >>>>> I have no audio on my internal speaker on the 396XT.
      >>>>> External speaker is extremely low at full volume. For 2 or
      >>>>> 3 days before it quit, the audio sounded a bit distorted.
      >>>>> Anyone have similar problems? Sending it to Uniden after
      >>>>> Xmas, under warranty. Thanks gang. Ed


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