Interesting thread over in rra.boatanchors suggesting that
ceramic capacitors' capacitance is voltage sensitive and
thus responsible for distortion in the audio path.

Brian Morrison wrote:

On Sat, 27 Oct 2018 12:59:58 +0100
Gareth's Downstairs Computer
wrote:

Interesting thread over in rra.boatanchors suggesting that
ceramic capacitors' capacitance is voltage sensitive and
thus responsible for distortion in the audio path.

Well known in SM caps with higher dielectrics, it's essentially a
piezo-electric effect.

Noticeable in PLL loop filters, a voltage transient on a tuning step can
be considerably extended and in extreme cases will be microphonic.

I was under the impression you shouldn't use them in the signal path,
just for bypassing. More expensive and bulkier technologies are needed
for big signal capacitors.

--

Roger Hayter

Roger Hayter wrote:
Brian Morrison wrote:

On Sat, 27 Oct 2018 12:59:58 +0100
Gareth's Downstairs Computer
wrote:

Interesting thread over in rra.boatanchors suggesting that
ceramic capacitors' capacitance is voltage sensitive and
thus responsible for distortion in the audio path.

Well known in SM caps with higher dielectrics, it's essentially a
piezo-electric effect.

Noticeable in PLL loop filters, a voltage transient on a tuning step can
be considerably extended and in extreme cases will be microphonic.

I was under the impression you shouldn't use them in the signal path,
just for bypassing. More expensive and bulkier technologies are needed
for big signal capacitors.

The true purist does not use capacitors in the signal path.
All DC-coupled amplifiers.

"Michael Black" wrote in message
news:alpine.LNX.2.20.1810271206170.5141@thrush...
On Sat, 27 Oct 2018, Gareth's Downstairs Computer wrote:

Interesting thread over in rra.boatanchors suggesting that
ceramic capacitors' capacitance is voltage sensitive and
thus responsible for distortion in the audio path.

Since it's audio, won't the capacitance values be high enough that you're
more likely to use electrolytics in the audio path?

Michael


If it is amateur radio audio, probably not.

PA

On Sat, 27 Oct 2018, Gareth's Downstairs Computer wrote:

Interesting thread over in rra.boatanchors suggesting that
ceramic capacitors' capacitance is voltage sensitive and
thus responsible for distortion in the audio path.

Since it's audio, won't the capacitance values be high enough that you're
more likely to use electrolytics in the audio path?

Michael

Rob wrote:

Roger Hayter wrote:
Brian Morrison wrote:

On Sat, 27 Oct 2018 12:59:58 +0100
Gareth's Downstairs Computer
wrote:

Interesting thread over in rra.boatanchors suggesting that
ceramic capacitors' capacitance is voltage sensitive and
thus responsible for distortion in the audio path.

Well known in SM caps with higher dielectrics, it's essentially a
piezo-electric effect.

Noticeable in PLL loop filters, a voltage transient on a tuning step can
be considerably extended and in extreme cases will be microphonic.

I was under the impression you shouldn't use them in the signal path,
just for bypassing. More expensive and bulkier technologies are needed
for big signal capacitors.

The true purist does not use capacitors in the signal path.
All DC-coupled amplifiers.

For communication purposes (and for any real speakers) then you need a
massive HPF to make the signal usable.

--

Roger Hayter

In message , Gareth's Downstairs Computer
writes
Interesting thread over in rra.boatanchors suggesting that
ceramic capacitors' capacitance is voltage sensitive and
thus responsible for distortion in the audio path.

Correct. They are piezo-electric by nature. The also exhibit dielectric
absorbance which is Bad News if you use then in a peak detector or
sample and leak ^H hold.

Silver mica or polypropylene is better. Some ceramic dielectrics also
vary wildly with temperature which can also give grief and sorrow.

I imagine that a combination of dielectric absorbance and capacitance
change will give audio distortion

B
--
Brian Howie

Il se trouve que Brian Morrison a formulé :

Well known in SM caps with higher dielectrics, it's essentially a
piezo-electric effect.

Noticeable in PLL loop filters, a voltage transient on a tuning step can
be considerably extended and in extreme cases will be microphonic.

+1
AFAIK ceramic capacitors are never used in audio except for RF
bypassing
and in parralel with other types of capacitors.

In article alpine.LNX.2.20.1810271206170.5141@thrush,
says...

Interesting thread over in rra.boatanchors suggesting that
ceramic capacitors' capacitance is voltage sensitive and
thus responsible for distortion in the audio path.

Since it's audio, won't the capacitance values be high enough that you're
more likely to use electrolytics in the audio path?




I got most of that started when I asked a question about someone
replacing paper capacitors with the ceramic disk in an old transmitter I
bought.

As the discussing is in boatanchors, it is mainly assumed to be old tube
equipment, which is what I have. Values around .01 to .1 mfd are often
used in the signal path. The impedances of the tube circuits are often
half a megohm and up. Outside of filter capacitors about the only place
in an audio circuit for electrolytics is in the cathode resistor bypass
where that resistor is usually under 500 ohms of tube circuits.

If lower impedance of transistors, then the value of the capacitors are
often high enough to go to electrolytics.