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<p>Hi, Bob,</p>
<p>I do not know how this applies today, but the intent in 1953 (of
which I have a good deal of documentation) is most officially
summarized in this (OCRd):</p>
<p>"IRE Standards on American Recommended Practice for Volume
Measurements of Electrical Speech and Program Waves, 1953"</p>
<p>Reprinted from the PROCEEDINGS OF THE I.R.E. VOL. 42, NO. S, MAY,
1954</p>
<p>"4.3 Ability to Withstand Overload. The instrument should
withstand without injury or effect on calibration, a momentary
overload of ten times the voltage corresponding to reference
deflection, and a continuous overload of five times that voltage,
because of the great variation in amplitude which this indicator
may encounter."</p>
<p>Note that "reference deflection" refers to 0VU, so +20 VU
momentarily and +14 VU continuously. Of course, add 4 to those
numbers to get dBu in today's standards, but when this was
written, the reference level for 0 VU was often +8 dBm (see EIA
RS-219, now withdrawn).</p>
<p>This standard also addresses my other pet peeve with VU meters:
When they are installed across an output line. Now, I know some
devices have a lower output impedance than 600 ohms, so this
doesn't apply, but still...</p>
<p>"4.2 Harmonic Distortion. The root-mean-square value of the
harmonic distortion produced when the volume indicator is bridged
across a resistive circuit impedance through which a sinusoidal
wave between 25 and 8,000<br>
cycles per second is being transmitted should not exceed 0.2 per
cent of the fundamental."</p>
<p>Other drafts of the standard say 0.3 per cent, but still...IMHO
all VU meters should be buffered.</p>
<p>Cheers,</p>
<p>Richard<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 2021-01-28 12:26 p.m., Bob Katz via
ProAudio wrote:<br>
</div>
<blockquote type="cite"
cite="mid:a46e95d8-2680-0b31-31d2-2a9feea3a87d@digido.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<p>This list has been remarkably silent, but I am very grateful
that it's around when I have a question to ask AUDIO EXPERTS.</p>
<p><br>
</p>
<p>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.</p>
<p><br>
</p>
<p><br>
</p>
<p>Thanks and happy New Year!</p>
<p><br>
</p>
<p><br>
</p>
<p>Bob<br>
</p>
<div class="moz-signature">-- <br>
<pre><font class="3D""" face="3D"Courier"">
If you want good sound on your album, come to
Bob Katz 407-831-0233 DIGITAL DOMAIN MASTERING STUDIO
Author: <b>Mastering Audio</b>
<a href="https://www.digido.com/" moz-do-not-send="true">Digital Domain Website</a>
No trees were killed in the sending of this message. However a large number
of electrons were terribly inconvenienced.</font>
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<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>
<a class="moz-txt-link-freetext" href="http://www.richardhess.com/tape/contact.htm">http://www.richardhess.com/tape/contact.htm</a>
Quality tape transfers -- even from hard-to-play tapes.</pre>
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