<div style="color:black;font: 12pt Arial, Helvetica, sans-serif;">Yes, increasing series R on the drive side will exaggerate magnetic non-linearities of the core material (i.e., THD). If you want to shift the mix of odd to even order harmonics, add a few mA of DC on the primary side (say 0 to 30 VDC through a 10 k-ohm resistor directly to the primary side.
<div><br>
</div>
<div>The R and C (in parallel) across the secondary will control the frequency and Q of the self-resonance.</div>
<div><br>
</div>
<div>You can read my "Audio Transformers" chapter in the Ballou "Handbook for Sound Engineers" for more details.</div>
<div><br>
</div>
<div>Bill<br>
<br>
<br>
<div style="font-family:arial,helvetica;font-size:10pt;color:black"><font size="2">-----Original Message-----<br>
From: Bob Katz via ProAudio <proaudio@bach.pgm.com><br>
To: proaudio@bach.pgm.com<br>
Sent: Sun, Jan 30, 2022 8:39 am<br>
Subject: Re: [ProAudio] Western Electric 111C transformers<br>
<br>
<div id="yiv2030202385">
<div>
<div>Now we're cooking!</div>
<div>Dear Bill: Thanks. <br clear="none">
</div>
<div>Yes, I am looking for color. I understand the series resistor.
I'll probably use a dialpot so I can log the setting for recall.</div>
<div>On the secondary side, are you suggesting a variable load R with
the C across it? <br clear="none">
</div>
<div>If I am looking for color and want to do some measurements to see
the effect of various source and load devices, clearly a square
wave investigation will tell me something. Frequency response will
tell me something. What about harmonic distortion... probably look
at THD at low frequencies???</div>
<div><br clear="none">
</div>
<div>Best,</div>
<div><br clear="none">
</div>
<div><br clear="none">
</div>
<div>Bob</div>
<div><br clear="none">
</div>
<div><br clear="none">
</div>
<div><br clear="none">
</div>
<div><br clear="none">
</div>
<div id="yiv2030202385yqt39568" class="yiv2030202385yqt9932338404">
<div class="yiv2030202385moz-cite-prefix">On 1/29/22 5:15 PM, Bill Whitlock via
ProAudio wrote:<br clear="none">
</div>
<blockquote type="cite">
</blockquote></div>
</div>
<div id="yiv2030202385yqt65427" class="yiv2030202385yqt9932338404">
<div>
<div style="color:black;font:12pt Arial, Helvetica, sans-serif;">If
you're after coloration, the strongest influencer of distortion
is source impedance, so I'd put something like a 1 or 2 k-ohm
pot (connected as a rheostat or variable resistor) in series
with the primary high side terminal. At high-resistance
settings, you'll' get some level loss - and possible
high-frequency loss if there's much capacitive load (or cable)
on the secondary side. Putting a variable load resistance on
the secondary, along with some intentional capacitive load to
bring resonance down toward 20 kHz) will allow control of the
resonance's Q. I don't recall off-hand where the natural
self-resonance of the secondary is, but I'd start with 1 nF or
so and use a 50 k-ohm pot (with a series 1 or 2 k resistor to
keep resistance from going to zero) variable load resistor.
Results will, of course, guide you from there!
<div><br clear="none">
</div>
<div>Bill Whitlock</div>
<div>AES Life Fellow</div>
<div>Whitlock Consulting</div>
<div>Ventura, CA<br clear="none">
<br clear="none">
<br clear="none">
<div style="font-family:arial, helvetica;font-size:10pt;color:black;"><font size="2">-----Original Message-----<br clear="none">
From: Bob Katz via ProAudio <a rel="nofollow noopener noreferrer" shape="rect" ymailto="mailto:proaudio@bach.pgm.com" target="_blank" href="mailto:proaudio@bach.pgm.com" class="yiv2030202385moz-txt-link-rfc2396E"><proaudio@bach.pgm.com></a><br clear="none">
To: <a rel="nofollow noopener noreferrer" shape="rect" ymailto="mailto:proaudio@bach.pgm.com" target="_blank" href="mailto:proaudio@bach.pgm.com" class="yiv2030202385moz-txt-link-abbreviated">proaudio@bach.pgm.com</a><br clear="none">
Sent: Sat, Jan 29, 2022 1:16 pm<br clear="none">
Subject: [ProAudio] Western Electric 111C transformers<br clear="none">
<br clear="none">
</font>
<div id="yiv2030202385">
<div>
<pre class="yiv2030202385moz-quote-pre">Hola, Guys. I’ve got a pair of these sitting around doing nothing. I’m sure their effect will be subtle but it might be nice to package them into a passive box for their color in a mastering session.
To vary their color would you have any suggestions on switchable buildout or termination resistors or zoebel networks I might want to add to the box, in addition to hard wire bypass?
Appreciate any suggestions. Thanks
Bob</pre>
<div class="yiv2030202385moz-signature">-- <br clear="none">
<pre><font 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 rel="nofollow noopener noreferrer" shape="rect" target="_blank" href="https://www.digido.com/">Digital Domain Website</a>
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<div class="yiv2030202385moz-signature">-- <br clear="none">
<pre><font 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 rel="nofollow noopener noreferrer" shape="rect" target="_blank" href="https://www.digido.com/">Digital Domain Website</a>
No trees were killed in the sending of this message. However a large number
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