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Johan wrote:
<blockquote cite="mid:1215240287.19635.8.camel@phoenix" type="cite">
<pre wrap="">On Fri, 2008-07-04 at 22:16 -0700, Alen Edwards wrote:
</pre>
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<pre wrap="">
James wrote:
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<pre wrap="">Roo wrote:
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<pre wrap="">2008/7/5 James Lockie <a class="moz-txt-link-rfc2396E" href="mailto:bjlockie@lockie.ca"><bjlockie@lockie.ca></a>:
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<pre wrap="">There is 0 volts on the RCA.
Why do I get sound if there is a zero volt signal?
I tested my voltmeter on a battery to verify it works.
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<pre wrap="">James,
If your voltmeter is on a DC range and the output is bipolar, +0.5V
and -0.5V then that will "average" out to 0V. This is irrespective of
the data travelling over the spdif as it is Manchester Coded.
Try an AC range on the voltmeter if you have one.
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<pre wrap="">AC is 3 something.
So if my receiver expects 5V and it is getting less, am I hurting it?
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<pre wrap="">HTH,
Roo.
___________________
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<pre wrap="">If you are getting 0 DC and 3AC, I am surprised. I would expect it to
be the other way around (0AC and 2-3DC). No matter, less it good and
your receiver is probably saying it can take anything up to 5 volts
and it can probably take much less, like maybe .1 volts. Some people
on this list have said their equipment works all the way to .025
volts. I would double check your numbers and readings then try it.
Allen
_
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<pre wrap=""><!---->Summarizing:
the signal is digital manchester coded and probably bipolar, so will not
contain a DC component.
It's sampling rate is up to 96kHz, to high for most multimeters.
Multimeters do not measure peak values, but only average (they are even
"calibrated" in RMS (root MEAN Square). So you will never know what peak
voltages are actually present.
Only way to be sure is to use an oscilloscope.
know it does not help, but clarifies a shortfall in the measuring
technique..
Johan</pre>
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</blockquote>
That is why I was surprised he measured 3 volts on AC and 0 on DC.
When I measured the output on my MB, it was between 2 and 3 on DC and 0
on AC for the reasons you state and the fact that the signal levels
were TTL and not spdif. I AC coupled and attenuated it so now I
measure 0 and 0. <br>
<br>
btw, you can measure the peak voltage if you use a diode and a small
capacitor in front of the DC voltmeter, but that is another discussion
and is not without its issues.<br>
<br>
Allen<br>
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