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Chapter 21 (well it was in edition 2) of Douglas Self's book on audio which should be on every audio engineer's shelf covers almost every way of muting a signal. One of those should suit you.</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Synth-diy <synth-diy-bounces@synth-diy.org> on behalf of Benjamin Tremblay via Synth-diy <synth-diy@synth-diy.org><br>
<b>Sent:</b> 08 May 2025 13:56<br>
<b>To:</b> synth-diy mailing list <synth-diy@synth-diy.org><br>
<b>Subject:</b> Re: [sdiy] Muting circuits for line out</font>
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<div dir="auto">The original design had the power switch on the volume knob. I suppose that was a way to mitigate this.<br id="x_x_lineBreakAtBeginningOfSignature">
<div dir="ltr">Benjamin Tremblay</div>
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<blockquote type="cite">On May 8, 2025, at 8:44 AM, Benjamin Tremblay <btremblay@me.com> wrote:<br>
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<div dir="ltr">Oh wait, I suppose the patent is for an fm signal that has not yet been demodulated.<br id="x_x_lineBreakAtBeginningOfSignature">
<div dir="ltr">Benjamin Tremblay</div>
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<blockquote type="cite">On May 8, 2025, at 8:30 AM, Benjamin Tremblay <btremblay@me.com> wrote:<br>
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<div>Hello,</div>
<div>I have this lovely Univox JR-5 rhythm machine I have modded with knobs to control the sound mix. The original circuit was high gain but impedance sensitive so it summed current, not voltage and was very </div>
<div>I added a simple op amp to handle the mix. When power is turned on there is a horrible thump that sounds like it is 100x too loud. </div>
<div>I have been looking for a simple muting circuit. When I was repairing a Roland MC-909 I saw the muting circuit was little more than a pair of BJTs shorting the signal path. </div>
<div>I also saw this novel patent which attenuates the signal without much voltage offset, maybe?</div>
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<a rel="nofollow" href="https://patents.google.com/patent/US4288753A/en" style="text-decoration:none"><font color="#000000" style="color:rgba(0,0,0,1)">US4288753A - Muting circuit with operational amplifier - Google Patents</font></a></div>
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<div>I really just need to prevent that initial thump. I’ll pick up a relay if that is best. </div>
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<div>Is there an easier solid-state solution? I don’t mind adding another buffer stage at the output.</div>
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<div dir="ltr">Benjamin Tremblay</div>
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