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<p>Thanks very much, Bill!</p>
<p>I'll post measurements when I'm done. <br>
</p>
<p><br>
</p>
<p><br>
</p>
<p>Best wishes,</p>
<p><br>
</p>
<p><br>
</p>
<p>Bob</p>
<p><br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 7/22/23 2:00 PM, Bill Whitlock
wrote:<br>
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<blockquote type="cite"
cite="mid:332932616.3134058.1690048850012@mail.yahoo.com">
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First, you'll get a lot more "effect" from el-cheapo transformers
(smaller cores) rather than better ones like the 111's.
<div><br>
<div>Second, the chances of any significant remanent
magnetization depends on many things. Higher DC current
increases risk, of course, but technically the width of the BH
loop of the core material also has a huge effect. In general,
steel has the widest and high-nickel alloys (like Permalloy)
have the narrowest. But then you may like the sound of a
magnetized core. It will have stronger even-order harmonics
than odd, which normally predominate.</div>
<div><br>
</div>
<div>Cores can be demagnetized by driving them into saturation
with AC and then slowly reducing the AC amplitude to zero
(over a period of 15 to 30 seconds). Cores will, of course,
saturate with the least voltage at very low frequencies, say
10 or 20 Hz. Only one winding need be driven and you can tell
you've reached saturation by looking for flat-topping of the
voltage output at any other winding. Always check to be sure
the driving source isn't clipping when you think you've
reached the saturation point.</div>
<div><br>
</div>
<div>Bill Whitlock</div>
<div>AES Life Fellow</div>
<div>(from my new home in Chino, CA)<br>
<br>
<div id="ymail_android_signature"><a
id="ymail_android_signature_link"
href="https://play.google.com/store/apps/details?id=com.aol.mobile.aolapp"
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Android</a></div>
<br>
<blockquote style="margin: 0 0 20px 0;">
<div style="font-family:Roboto, sans-serif; color:#6D00F6;">
<div>On Sat, Jul 22, 2023 at 6:50 AM, Bob Katz</div>
<div><a class="moz-txt-link-rfc2396E" href="mailto:bobkatz@digido.com"><bobkatz@digido.com></a> wrote:</div>
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border-left: 1px solid #6D00F6;">
<div id="yiv3545024897">
<div>
<p>Hi everyone. Hope you're still around!</p>
<p>I'm finally getting to finding time to build my
"ultimate transformer color box". <br clear="none">
</p>
<p>Back in January, 2022, Bill Whitlock wrote:</p>
"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."
<p>My box contains a pair of WE111 and a pair of UTC
A-20. Two sets of transformers with distinctly
different saturation characteristics. It uses a
couple of Wayne Kirkwood mastering insert relay
boards to optionally insert a variable series
resistor, and to switch in one or the other
transformer.</p>
<p>Attached is a schematic for those who are
interested. Simple stuff, but fun!<br clear="none">
</p>
<p>I wasn't planning on having a DC injection circuit,
then it occurs to me I have a spare pair of relays.
I'm trying to keep the box totally passive, so the
question is how to handle the DC injection. We don't
know what the source will be as it could be from any
of my mastering gear, which is typically an active
balanced output. With relays I could insert a large
series capacitor to keep the DC injection from back
feeding into the balanced source. block the DC
injection from contaminating the source, plus the
variable DC injection into a transformer primary.
How does that idea sound to you?</p>
<p><br clear="none">
</p>
<p>Next question: Should I worry about the DC
injection circuit permanently magnetizing the core
of a transformer?</p>
<p><br clear="none">
</p>
<p>Best wishes,</p>
<div id="yiv3545024897yqtfd99351"
class="yiv3545024897yqt0279830658">
<p><br clear="none">
</p>
<p><br clear="none">
</p>
<p>Bob</p>
<div class="yiv3545024897moz-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/" 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>
</pre>
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</div>
</blockquote>
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</blockquote>
<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/">Digital Domain Website</a>
No trees were killed in the sending of this message. However a large number
of electrons were terribly inconvenienced.</font>
</pre>
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