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<div><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Most standard ceramics aren't suitable, due to both reasons you mention.</span></div>
<div class="elementToProof"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"><br>
</span></div>
<div class="elementToProof"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">However Samsung Electro-Mechanic do a range of special automotive grade ceramics that
eliminate the microphony problem. These are used extensively in the automotive industry for sensors and audio applications, as you can imagine a car is a never ending source of thumps and thuds to the electronics no matter how much damping you put in.<br>
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<div class="elementToProof"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</span></div>
<div class="elementToProof"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">There is also a TI paper examining how you can use X7Rs in most critical audio pathways
by careful design. Google for it.<br>
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<div class="elementToProof"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"><br>
</span></div>
<div class="elementToProof"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Electrolytics are the usual solution though.<br>
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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 Richie Burnett <rburnett@richieburnett.co.uk><br>
<b>Sent:</b> 29 November 2023 16:20<br>
<b>To:</b> synth-diy mailing list <synth-diy@synth-diy.org><br>
<b>Subject:</b> [sdiy] High-K ceramics and audio</font>
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<div class="PlainText">I'm assuming the use of small high dielectric constant ceramic capacitors
<br>
like 0805 4.7uF X7R for audio coupling applications is a bad idea due to the <br>
voltage coefficient?<br>
<br>
Most of the audio gear I've opened up seems to have surface mount <br>
electrolytic capacitors providing AC coupling between amplifier stages, or <br>
in places like the DC-blocking at the audio inputs and outputs of CODEC <br>
chips? Given that electrolytic capacitors are larger, heavier, more <br>
expensive and will eventually dry out, they must be superior to high-K <br>
ceramics in these applications?<br>
<br>
Is the problem with ceramics distortion caused by the non-linear dielectric? <br>
I can see how the change in capacitance with applied voltage could lead to <br>
distortion in applications where there is a large voltage swing across the <br>
ceramic capacitor. However, in cases where a DC-blocking (coupling) <br>
capacitor is sized quite large there wouldn't be that much voltage swing <br>
across it due to audio even down at 20Hz surely?<br>
<br>
Or is the issue microphony? I have certainly observed DC-blocking caps at <br>
the front end of a high-gain amplifier (not audio related!) that caused a <br>
very significant disturbance at the amplifier output when the PCB was tapped <br>
with a pen! (This seemed worse when there was DC bias across the <br>
capacitor.)<br>
<br>
I'd be interested to hear your thoughts. (I hope I haven't opened a can of <br>
worms with this topic !?)<br>
<br>
-Richie,<br>
<br>
<br>
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