The use of polypropylene capacitors and their effect

[Planobilly]

Hi guys,

Due to some non related issues with the AB763 new amp build I changed all the caps to Cornell Dubilier "orange drop" 715P polypropylene caps.

I was very surprised at the improvement in the sound quality. I realize that "sound quality" is pretty subjective. Whether the sound was truly "improved" or not, it certainly did change the sound and by an amount that was surprising to me.

What  experience have you guys had will different brands and types of capacitors? 

Billy

[Willabe]

....I changed all the caps to Cornell Dubilier "orange drop" 715P polypropylene caps.

What cap brand did you start with?

What  experience have you guys had will different brands and types of capacitors?

Look at this thread on coupling caps;

http://el34world.com/Forum/index.php?topic=19534.msg202775#msg202775

[labb]

I just finished a AB763 and I used Mallory 150's. Sounds pretty good. Friend of mine is using it. He played as a cover for a group last gig and the guitar player for the other band asked could he use it..When he got thru he said that it sounded as good as the Budda he had in the van..If you are getting that much difference with the Orange Drops I just might give them a try on the next one.

[Planobilly]

I started out with  the same brand, Cornell Dubilier. They were much smaller form factor 630V. I am not sure what material they are made from.

Generally I get a lot of components from Digi-Key and the first set came from them.  The Orange drop caps came in a assortment from CE Distribution which is one of the wholesale companies I deal with. One or two of the first set I ordered from Doug.

The orange drops were 600V and a much larger form factor cap.

I replaced all the cap at one time so it is entirely possible that only one of the first caps could have been defective.

 Me saying they sound better is totally subjective. They did in fact sound considerably different.

I don't have the equipment or the skill sets for that matter to do really reliable electronic testing. I assume that I am not much different than most hobbyist/guitar players and have my on bias as it relates to this subject. I also have a bit of hearing loss at around 18K Hz.

There is an endless amount of conversation that goes on regarding the sound of components that appears near impossible to actually measure and virtually no double blind testing is ever done.

I have some communication at times with a few highly educated electronic engineers. While these individuals know a ton of stuff they have little experience with vacuum tube electronics. They also have zero experience playing guitar or music or any kind for that matter. If one does not play guitar, I think it is very hard to conceptualize the interactions that occur between the player and the electronics.

At the end of the day, I think personal experimentation is the only thing that is actually very relevant. If it sounds good to you then it the "best" component to use. Well...at least until the next day when you get up on the other side of the bed and change your mind...lol

Cheers,

Billy         

[HotBluePlates]

Me saying they sound better is totally subjective. They did in fact sound considerably different.

I believe you heard what you heard.  In some amps I've heard polypropylene caps to have more treble and a more-solid bass compared to polyester caps.

In some amps I've heard no difference when switching cap types.

I would guess you had polyester caps before.  Polyester film & foil will be smaller than polypropylene caps.  Metallized polyester will be smaller still.

Size depends on the dielectric coefficient of the cap's insulation, the plate area and the voltage rating.  Some insulating materials yield more capacitance than others (dielectric constant).  Some materials are more easily ruptured by voltage, and need a thicker layer of insulation.  That moves the conductive plates further apart, reducing capacitance.  To compensate, the conductive plates are made larger to raise the capacitance back up.  Overall, the cap gets larger for the same value & voltage rating.

It turns out that the "more perfect" dielectrics also have a small dielectric coefficient, and yield less capacitance for a given plate area.  So you can roughly assume that the bigger cap for the same value/voltage is closer to the "ideal capacitor".

Whether it is audibly-better depends a lot on how it's used in the circuit, and the characteristics of the audio signal.  Some folks also really like caps which sound like those used in vintage amps, which arguably were not very good caps by modern standards.

[Planobilly]

Hi HotBluePlates,

The whole issue of the size of a capacitor has always been a bit perplexing to me. I understand that modern capacitors are frequently much smaller than those from the past due to improved materials availability.

I see Mesa Boogie for example using United Chemi-Con 220uf filter caps in their power supplies. Those caps are almost twice as large as other brands of the same capacitance, voltage, and heat ratings. I have replaced them when they failed with other brands like F&T for example because my normal source of supply could not provide them and I was unwilling to pay Mesa's price. I could not tell any difference between the them but that does not mean it does not exist.

Your comment about "more perfect" dielectrics caught my attention. That makes me wonder if that is what Mesa had in mind. I think Mesa tries pretty hard to make good amps and while cost of components would certainly be a consideration for Mesa, cost may not be the issue in this case.   

I am not sure that me changing all the caps to orange drop was a good idea or not. The amp sounds really good to me but I have have no idea of what other possible detrimental conditions were introduced as a result of the change. I guess if the amp continues to play well over time the change had no ill effect

In any event this is an experimental amp built specifically to try different things with. Producing failures is as important to me as producing beneficial changes. I want to know for myself what works and what does not and why to the best I can. 

I highly recommend starting to learn electronics before you reach seventy...lol

Thanks,

Billy

[Willabe]

Read the thread on 'do caps sound different' I posted the link to. A lot of good info in there. 

[HotBluePlates]

... I understand that modern capacitors are frequently much smaller than those from the past due to improved materials availability.

I see Mesa Boogie for example using United Chemi-Con 220uf filter caps in their power supplies. Those caps are almost twice as large as other brands of the same capacitance, voltage, and heat ratings.  ...

Electrolytic caps are in a different category in some ways than everything else I was talking about.  By that I mean there is a lot of ongoing development in electrolytic caps, and a great many different categories of them.

But consider this:
Among all caps, electrolytics are considered the "worst" as far as behaving most closely to an ideal cap (though we're talking about so many different types by saying "electrolytic" that it's a little unfair to make this claim).  But whatever the size difference among individual electrolytics, they are all small compared to a film cap of the same capacitance.  See for example the 27µF polypropylene film cap below compared to a couple of 22µF electrolytic caps.

[Planobilly]

Hi guys,

I took the time to read all of the "do caps sound different" thread. It was informative and interesting. Some of the apparent results matched very closely with what I have discovered more or less accidentally.

I think it will always be difficult to make definitive statements about a certain brand or type of cap for a certain use as far as tone goes. There are a ton of variables and the cost to prove or disprove are most likely out of reason for the likely results.

 I have some experience with testing thin film coatings produced in a gas plasma. We found it very difficult to set up repeatable testing methods to prove or disprove certain characteristics. Also the cost of the testing quickly got to be very expensive. Other exposure to testing in aerospace indicated many difficult issues with the world of testing.   

Thanks to everyone for all the new insight into caps! Day by day I am learning new things and this is a fun road to be traveling.

Thanks,

Billy   

[SoundmasterG]

Another thing to keep in mind about the Orange Drop 715P's, aside from them being polypropylene is that they are made with film/foil construction, which always results in a larger cap than one made with metallized construction such as the Mallory 150.


Greg