I've heard that metalized polypropylene capacitors aren't as good as foil and polyprop caps. Something to do with residual charge not draining off as quick due perhaps from resistance of the metalization. I wonder if the diff is significant? Does one sound better than the other?
The ESR is slightly higher for metallized, as is max ripple current. For coupling use, the difference is insignificant. For high ripple current applications, the foil cap will be better.
Is that because of the resistance of the metalized layer vs the thicker foil? Just curious.
G²
I don't recall the specifics of polypropylene, but in mylar the metallized film is preferred in line V applications because the arc in local breakdown in the dielectric can "clear" by eroding the thin metallization in the vicinity of the arc
with foil electrodes a dielectric breakdown, not limited by external impedance, will destroy the Cap
in fact , some "metallized film" polypropylene use double sided metallized mylar as the electrodes
for low esr and high SRF you really want "extended foil" construction where the foil edges are shorted by endcaps/spray metallization/ultrasonic welding
with foil electrodes a dielectric breakdown, not limited by external impedance, will destroy the Cap
in fact , some "metallized film" polypropylene use double sided metallized mylar as the electrodes
for low esr and high SRF you really want "extended foil" construction where the foil edges are shorted by endcaps/spray metallization/ultrasonic welding
DA is important if you're making timers. The metallization vs foil is pretty irrelevant for that- it affects ESR.
More curiosity. Would the 'islandy' nature of the film mimic DA?
I think the poor conductivity of the coating on CRTs causes them to 'recover' a charge after shorting them out. I always thought the discharge causes a voltage gradient around the anode connection because of the resistance caused slow discharge. The 'recovery' is just the charge migrating through the high resistance coating to equalize the charge. Doesn't this mimic DA?
G²
More curiosity. Would the 'islandy' nature of the film mimic DA?
I think the poor conductivity of the coating on CRTs causes them to 'recover' a charge after shorting them out. I always thought the discharge causes a voltage gradient around the anode connection because of the resistance caused slow discharge. The 'recovery' is just the charge migrating through the high resistance coating to equalize the charge. Doesn't this mimic DA?G²
Resistance, either internal or external, is not the same as DA. Distortion analysis will reveal the difference. Internal resistance would add to external resistance and alter the RC time constant of whatever circuit is being used. DA would still be the same.
More curiosity. Would the 'islandy' nature of the film mimic DA?
No. It's a pure resistance and a damn small one. With a high DA, you can charge up a cap, discharge it, then open circuit it, and you'll see voltage build back up- memory, as it were. It's mostly a function of dielectric. ESR is just a simple resistance, on the order of milliohms.
DA in itself is a linear phenomenon, and doesn't cause distortion.Resistance, either internal or external, is not the same as DA. Distortion analysis will reveal the difference. Internal resistance would add to external resistance and alter the RC time constant of whatever circuit is being used. DA would still be the same.
It is true however that dielectrics having a high DA often happen to be non-linear, but that's incidental and another story.
Probably not, but I was just correcting the assertion that "distortion in capacitors is caused by DA".DA might be linear, but is it good for an audio circuit to remember the signal which was passing through a few seconds ago?
The effect is to alter the phase and frequency responses.
But this effect has to be put in perspective too: it can only manifest itself where the capacitor is used as a reactive element, which is not the case in coupling or bypassing applications, that is over 90% of capacitors in audio.
In filters, it does matter, but in general, the effect will be very small compared to the "normal" filtering action of the network, and even in high Q active filters, it is normally sufficient to simply include it in the generic losses, the tan delta.
It does a bit of both, short term and long term.Or does DA just remember the signal average, which will normally be around zero
Probably not, but I was just correcting the assertion that "distortion in capacitors is caused by DA".
If not DA, what phenomenon causes distortion in capacitors?
In what use? Different applications have different requirements and different distortion mechanisms.
All audio applications. Other than DA effect, how can distortion be generated?
All audio applications. Other than DA effect, how can distortion be generated?
External vibration. self excited vibration, wire to foil connection contamination, moisture contamination, changes in value due to applied voltage, tribo electric effect, and of course the best known external fields the outside foil.
External vibration. self excited vibration, wire to foil connection contamination, moisture contamination, changes in value due to applied voltage, tribo electric effect, and of course the best known external fields the outside foil.
I have never observed ill effects from the above sources. Most caps manufactured today no not suffer from these maladies, especially film caps.
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