Do electrolytic caps need burn in?
Pass doesn’t use ELNA silk caps. I’m pretty sure he doesn’t use electrolytic coupling caps anywhere! :) But I read somewhere he recommended them as the best of electrolytic bipolar caps. Possibly from here: https://www.head-fi.org/threads/elna-silmic-vs-silmic-ii.405280/ Best, E |
After sorting through all the choices, I finally settled on a huge pair of polypropylene 1000uF caps made for commercial power supply applications (solar power). I found them cheap on ebay. I got them custom mounted. All the highs and the details are there. Very well balanced cap.The value of the part can make a difference. There is more nuance to power supply design than initially meets the eye. If the cap values are too large, the impedance curve of the output of the supply might not be a good bypass at high frequencies even though the overall output impedance might be lower. If too small, bass might not be well bypassed. This can change depending on the performance of the caps used- better caps can often be larger values. But you have to watch your timing constants (as a general rule of thumb, the TC of the power supply should be at least an octave lower than the TC of the audio circuit its supplying, and not much more!) and if you have regulation, many regulators won't be happy with larger values (and might have shorter lifespans too). This is the tip of the iceberg! I would not write off conventional electrolytics though; if used correctly they can perform as well as film caps. If. Used. Correctly. YMMV but IME we've had terrible luck with using more exotic electrolytic capacitors; they don't seem to work as well as more middle-of-the-road parts. Quite often they wind up sounding dark. |
Hi @atmasphere , the cap I was discussing was actually being used for output coupling in an amp/preamp. Stock value is very large, because the circuit is meant to drive a speaker load. I noticed the Mundorf EL cap in this location was inherently dark sounding (no highs). Anyways, thanks for the comments. Im currently happy with the large polypropylene film caps that are in use (havent touched them). At 1000uF and high voltage rating, they are as big as the chassis for the amp haha |
Once the electrolytic has formed up, it should work about as well as the film caps in a coupling cap situation, so long as its biased correctly. To this end, whatever AC voltage is being sent through it as an audio signal should never exceed the DC voltage on the cap. I don't know how a coupling cap in a traditional solid state output could do that- The DC on the cap would be 1/2 of the power supply voltage and the output swing of the amplifier could be nearly rail to rail. So in such a circumstance the cap would make considerable distortion. I think this is one of the ways electrolytics have gotten a bad rap in audio as coupling caps. |
That is true. My preamp puts out about 6v DC, and the AC signal component would have to exceed 2Vrms to cause the polarity to flip on the cap. That kind of level would exceed my amplifier sensitivity by 2x. Needless to say, I dont listen very loud, so in my application, I could safely say the polarity of the EL cap was never dynamically reverse biasing. Thus, it had no bearing on the sound I was hearing. All of the EL caps I tried (after lots of hours to form) were all lacking detail and lacking HF content. This was a common theme, although some fared better than others. |
