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Author Topic: What kind of capacitors to use where??  (Read 1863 times)


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What kind of capacitors to use where??
« on: March 03, 2019, 08:16:46 AM »
So I know Electrolytics for power supply filtering, however when I look on Digikey brands like Nichicon have multiple of seiries of Electrolytics to choose from..  all having the capacitance and voltage rating I am looking for..  How does one choose??  Go fot the highest ripple current/lifespan I can find??

Also, when it comes to tonestack/signal path caps, what types are people using?  I've read to avoid ceramics due to temperature instability and being somewhat microphonic.  When I've opened up other amps I've seen a a lot of orange and green caps..  Can somebody let me know what the orange and green caps I have seen in other amps are made of, and/or who makes those kind of caps?  Orange drop caps??  Whats the deal with tropical fish caps..  Should they be something I should look into?

Other than that, it looks like caps can get a little expensive..  So I guess I have some research/math to do.. 


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Re: What kind of capacitors to use where??
« Reply #1 on: March 03, 2019, 12:55:08 PM »
The electrolytic caps can be in several diff types of packages so that might be one issue with finding a lot with the same Uf values and the same voltage ratings? The 3 most often seen are the Radial, Axial and Can Capacitor. Generally you don't see Can capacitors in SS amps but were quite common in the vintage tube amps. The Radial caps with the two long wire leads coming from one end would be most common to use in more modern amps with smaller printed circuit boards (pcb). The Axial type with one wire coming out of each end are found more often in amps with older and bigger pcbs where there is more room on the board for the caps to lay down. I am a fan of Nichicon, Spraque, Mallory, Panasonic.....just about any electrolytic caps made in the US or Japan.

Regarding the non-polarized capacitors used for coupling gain stages together, commonly referred to as tone caps. I don't know what the orange and green ones would be without seeing them. But the different brands can be found as the predominant "tone" caps in different amp manufaturer's products. Generally speaking, the less expensive the amp, the less picky the manufacturer is about the brand/quality of the parts they use. People who build the much higher priced amps are trying for the best product possible and they buy the tone caps they believe sound best in their amplifier. I don't remember most of the better tone cap maker's names right off my head, but you can always buy a few different kinds in small amounts and see which ones sound best to you. I would say go to a website dedicated to offering the best amp materials and peruse the diff capacitors they sell. (try Antique Electronic Supply, Tube Depot and EL34 World which all carry quality parts)

Big word of caution:  Electrolytic capacitors work like batteries storing energy so the amp doesn't warble in and out when the circuit calls for more power. But depending on what type of electrolyte material used in the capacitor, all of them eventually dry out and no longer hold the energy. So, that said, don't buy "vintage" electro caps because they can be no good right out of the box.


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Re: What kind of capacitors to use where??
« Reply #2 on: March 03, 2019, 08:41:50 PM »
You mentioned ripple current and lifespan, for electrolytics also look at the temperature rating and opt for the higher temp if you can.  It will usually further extend the lifespan.


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Re: What kind of capacitors to use where??
« Reply #3 on: March 24, 2019, 09:54:39 PM »
Electrolytics come in 85 degree and 105 degree.  You might as well spend the extra few cents for the higher temp caps, as they will have longer life in the hot amp environment.  Beyond that I pick the shape that best suits my need, and then I pick for cheapest.

Mouser doesn't sell anything I'd consider junk, so go with cheapest there.   You can worry about paying premium pprices later in your career.