|
Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
|
|
|
Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
|
In Reply to: film cap questions -- share your views please posted by mschneider on May 16, 2009 at 17:22:47:
In general, use a PE cap only if you don't have a good alternative option.
Loudspeaker crossovers are one of the most revealing and difficult applications for a capacitor, and it becomes more readily apparent when quality has changed.
Some 19 years ago, I persuaded my boss to listen to the difference that changing to metalized PP caps, from metalized mylar (PE) made.
An A/B was set-up, with all the same components, except for being able to switch out the crossover caps in the circuit, PE vs. PP.
He was a skeptic, he didn't WANT to pay any more money, even the slight premium to go from PE to PP, so he entered into the whole affair with a strong bias against hearing anything, much less something he would have to pay more money for.
We started up the listening test, and he didn't know which switch position was which type of cap, and we just happened to start off with the good old mylars in the circuit. Then we flipped the switch, and his jaw dropped, his eyes went wide, and we spent the next hour helping him figure out just exactly how we were going to sell the change to HIS boss.
Mylars are a good step up from electrolytics, or cheap Z5U or X7R ceramics, but they just aren't as clean and clear as a good PP cap.
Not all of the sonic difference is in the mids and highs either, PE can make the bass sound woolly or slow, even bloated or a bit boomy, compared to a superior dielectric. While this can make it seem to have a stronger bass response, it is a false, less accurate response, and one that covers up the midrange as well.
The sonic differences when caps are in line level coupling are less dramatic than when used for loudspeaker crossovers, and depends a lot on how "loaded down" the caps are in terms of the following stage input impedance. If they are loaded with a lower impedance, then unless the value is raised proportionately to more than compensate, they start to approach the sonic behavior in amp level crossovers. If they are lightly loaded, and have an adequately low roll-off frequency, they will exhibit less of their characteristic sound than when heavily loaded.
Bottom line: don't use PE unless you have to, due to cost, size or some other overriding consideration.
On the other hand, going all out and using Teflon may be overkill for a lot of projects, as a decent PP or metalized PP can do pretty good sonically.
Teflon is justified when pursuing the SOTA, or cost is not a factor, etc., or for a few critical coupling locations in a circuit, such as a negative feedback leg, etc.
Jon Risch
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: film cap questions -- share your views please - Jon Risch 20:56:53 05/19/09 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
