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<p>Hi, Jay,</p>
<p>The language I posted from the IRE 1954 publication says
***five*** times for continuous overload. Where did your "three
times" wording come from?</p>
<p>The 1940 Chinn article you link to states, "5. Overload The
instrument is capable of withstanding, without injury or effect
on calibration, peaks of 10 times the voltage equivalent to a
deflection to the 0-vu or 100 mark for 0.5 second and a
continuous overload of 5 times the same voltage." (cut and pasted
from the link in your message).<br>
</p>
<p>What triggered me to look was I had said "+20 VU and +14 VU,"
while you said "+20 dB and +10 dB," so I wanted to make certain
one of us hadn't made a silly math mistake. We hadn't. We had
different versions of the text.</p>
<p>Another discrepancy: The text I cited did not provide specific
times, but said "momentary" and "continuous." The quote from the
Chinn paper is "0.5 second" while the quote you posted below is "5
s."</p>
<p>We need someone to say, "The nice things about standards is we
have so many!" Oh, I just did!<br>
</p>
<p>One minor nit. The VU is relative to reference level and as
measured on a VU meter. Therefore, I think it is less ambiguous to
make it clearly relate to the reference level as shown on the
meter, one should use "VU" rather than "dB." In the common common
practice today with 0 VU = +4 dBu, that would be +24 dBu for 5 s
(or 0.5 s) and either +18 dBu or +14 dBu (five or three times the
overload) continuously. Of course, back in 1954, 0 VU was most
often +8 dBm, so different levels would prevail.</p>
<p>Cheers,</p>
<p>Richard<br>
</p>
<div class="moz-cite-prefix">On 2021-01-28 10:15 p.m., Jay at MRL
Support via ProAudio wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1598380530.20210128191514@comcast.net">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Re: [ProAudio] VU meter permitted overdrive with a sine
wave...</title>
<span style=" font-family:'Times New Roman'; font-size: 12pt;">Hello
Bob,<br>
<br>
It appears that no-one has ever read any of the once-published
standards on the vu meter. <br>
<br>
<span style=" font-size: 11pt;">"15 Overload input level <span
style=" font-size: 18pt;">- <span style=" font-size: 11pt;">Performance
requirement<br>
"The indicator shall withstand, without damage or any
effect on calibration,<br>
an overload of ten times the voltage giving reference
indication for a time<br>
interval of 5 s and an overload of three times that
voltage for unlimited<br>
period of time. "<br>
<br>
That would be +20 dB and +10 dB, respectively<br>
<br>
<span style=" font-size: 12pt;">This same text is in the
original Chinn IRE ~1940 paper ( </span></span></span></span></span><a
style=" font-family:'times new roman'; font-size: 12pt;"
href="https://www.aes.org/aeshc/pdf/chinn_a-new-svi.pdf"
moz-do-not-send="true">https://www.aes.org/aeshc/pdf/chinn_a-new-svi.pdf</a><span
style=" font-family:'Times New Roman'; font-size: 12pt;"> ),
the IRE Standard, the IEEE Standard, the ANSI Standard, or the
current Standard, IEC 268-17.<br>
<br>
On Thursday, January 28, 2021 at 9:26, you (Bob Katz via
ProAudio) wrote:<br>
<br>
</span>
<table>
<tbody>
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<td width="112" bgcolor="#0000ff"><br>
</td>
<td width="1190"><span style=" font-family:'Times New
Roman'; font-size: 12pt;">This list has been remarkably
silent, but I am very grateful that it's around when I
have a question to ask AUDIO EXPERTS.<br>
<br>
Who here knows the acceptable rating of a standard
mechanical VU meter above 0 VU with a sine wave? If I
recall correctly, they are designed to accept as high as
+6 VU or even higher. For example, when doing testing of
a tape recorder for headroom. It's still ideal to shut
off the meter, but in some cases that's not possible.<br>
<br>
<br>
Thanks and happy New Year!<br>
<br>
<br>
Bob<br>
-- </span></td>
</tr>
</tbody>
</table>
<br>
<br>
<span style=" font-family:'calibri'; font-size: 9pt; color:
#c0c0c0;"><i>-- <br>
Best regards,<br>
Jay McKnight <br>
at<br>
Magnetic Reference Laboratory, Inc </i></span><a style="
font-family:'calibri'; font-size: 9pt;"
href="mailto:mrltapes@comcast.net" moz-do-not-send="true">mailto:mrltapes@comcast.net</a><br>
<br>
<span style=" font-family:'calibri'; font-size: 9pt; color:
#c0c0c0;"><i>Technical Information only: Sales
information and orders:<br>
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Dr. <br>
Cupertino, CA 95014 US San Jose, CA 95123 US<br>
<br>
Tel +1 408 252 7396 Tel & FAX: +1 408
227 8631<br>
<br>
See our website for technical and ordering information:<br>
</i></span><a style=" font-family:'calibri'; font-size: 9pt;"
href="http://www.mrltapes.com" moz-do-not-send="true">http://www.mrltapes.com</a>
<br>
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</blockquote>
<pre class="moz-signature" cols="72">--
Richard L. Hess email: <a class="moz-txt-link-abbreviated" href="mailto:richard@richardhess.com">richard@richardhess.com</a>
Aurora, Ontario, Canada <a class="moz-txt-link-freetext" href="http://www.richardhess.com/">http://www.richardhess.com/</a>
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