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power supply filter caps, types affect sound?

7/31/2000 12:48 AM
power supply filter caps, types affect sound?
I have never used anything but electros for power supply filtering, but have read a bunch of stuff recently about the solen fast caps and polypropelene and oil types. it seems as though either of these would be a better choice. my question is, do electros have a "sound" to them? they must have a way of affecting the sound the other types do not (why else would any one spend nearly $100 on black gates?) I'd like to hear what anyone has to say about this.  
thanks, Josh
7/31/2000 10:48 AM
Stephen Conner

"(why else would any one spend nearly $100 on black gates?)"
Because it's the Black Gate capacitor co's moral duty to part suckers and their money. The caps don't actually have to make any difference to the sound, as long as people believe they do, the experimenter expectancy effect will do the rest.  
A far more compelling reason to use plastic film filter caps is that they last for ever. No more cap jobs. You shouldn't need to cough up $$$ for audiophile grade - industrial motor run caps will do. The working voltage quoted for motor run caps is RMS AC, so you can use them with DC up to 1.4x that.  
Steve C.
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7/31/2000 1:55 PM

Steven has it right - electros may have a sound, but spending $100 to get it isn't high on anyone's practicality list. AS he mentions, the reliability aspect is very important. Good film caps will last literally forever if they're not overstressed. Electros will definitely age, let hum through, and finally fail.  
A good source for film caps that are RUGGED is AC motor run capacitors. These things are polypropylene film in oil, and are usually available for something like $1 per uF or less depending on your source. If you get them from a surplus dealer, maybe lots less. These caps are designed for long life with high currents through them. They're part of my concept of the "Immortal Amplifier".
7/31/2000 4:20 PM

R.G., you said electros have a sound, what exactly is that sound, compared to the other types?  
7/31/2000 4:53 PM
R.G. Electrolytic capacitor sound
There is a small nonlinearity in the impedance of electrolytics. In circuits where the impedance of the electro is comparable to the impedance of the rest of the circuit it's connected to, this nonlinearity can sometimes be heard.  
I've heard lots of different descriptions of the sound, not many of them similar, and none of them complementary. Generally, any comparison is ended with "and when we put in the film capacitors, the sound was significantly better." I don't have a ready description of the nature of the distortion, so I can't make distinctions between brands and kinds.  
My cut on that is to not choose between different shades of ugly, but to step outside the region where electrolytic distortion matters. You can do this by making the impedance of the electro very small compared to the rest of the circuit, so variations of its impedance aren't noticeable, or going to a capacitor that has much lower level of nonlinearity by using something like film caps.  
As to comparing among technologies, in general the reputation is:  
Polystyrene, teflon - the very best, non colored and clear.  
polypropylene - almost as good as PS and TF  
polycarbonate - not quite as clear as PPL  
polyester/Mylar - still good, but a step down from PC  
Ceramic - Z5U versions sound gritty  
In general, stacked foil and noninductively wound will be better sounding in most cases than ordinary wound caps, but that's a pretty fine point - sorting between very close shades of gray.
9/7/2000 6:10 AM

R.G I will try to post a link to some interesting reading for you..  
9/7/2000 6:23 AM
R.G. I liked this part... I guess others hear differences too
Sure is alot of info.. here's the paragraph i liked..  
"It is not surprising to us that this type of reaction occurs, since one single polyester or electrolytic (or other polar type) can be heard, and a typical update to an old preamp or amp might replace a dozen or more! If you did nothing more than take an old (stock) Dynaco PA5 preamp and change the capacitors to polypropylenes, you can be literally astounded at the results. All of this is available at moderate cost to anyone who can solder, and you need not send your amp off to the specialty audio shop either! (Capacitor sources are listed in the appendices."  
All the threads on here about the different caps..and the tone or sound change..looks like others hear it too.  
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