[doobooloo]

In the past I've always used the large Panasonic P series polypropylene film caps (not metallized film) for the PPA bass boost cap (C7). While this technically was the superior cap type, the large size made it a hassle to implement in many cases.

Recently I ran across some nice WIMA metallized polypropylene (MKP2) and polyester (MKS2) box cap parts offered by Mouser that will fit the PCM5 footprint nicely. I ordered both types, since for the polypropylene 0.22uF was the largest in-stock item they had which is slightly lower than what I'd like, and the only suitable 0.47uF parts in stock were the polyester ones.

I am wondering... will I hear a noticeable sonic degradation going from the nice Panasonic P polypropylene film to WIMA metallized polyester? Strictly the polyester caps are sonically inferior but this is in a bass boost application, so I'm wondering if differences in quality of caps are as relevant.

Has anyone tried both types?

It would be awfully nice to be able to just pop in a PCM5 box cap instead of trying to creatively mount a huge epoxy coated cap and not worry that the sound is noticeably inferior... Any help would be greatly appreciated! Thanks!

 

[amb]

Quote:

Originally Posted by doobooloo Strictly the polyester caps are sonically inferior but this is in a bass boost application, so I'm wondering if differences in quality of caps are as relevant.

Yes it is relevant. Even though the cap is for bass boost, the way it works is that it acts as a high-pass filter in the feedback loop, with the response shape being a "shelved" shape. When bass boost is turned on, bass is being "blocked" but higher frequencies are going through this capacitor. This makes the cap quality important because it is directly in the signal path (albeit in the feedback loop, but nonetheless).

Whether you might actually hear a difference between a high quality polyester film cap or a metallized polypropylene cap is an open question, though.

 

[Daroid]

Quote:

Originally Posted by amb Whether you might actually hear a difference between a high quality polyester film cap or a metallized polypropylene cap is an open question, though.

You mean in general i suppose ?

It is a topic which often appears:
http://www.diyaudio.com/forums/showt...654&highlight=
http://www.diyaudio.com/forums/showt...588&highlight=

A little off-topic maybe, but getting 1uF film-type caps for the SDS labs h.amp with a raster of 15 mm is impossible with polypropylene, correct ? If i can find some polypropylene type caps which are smaller than a relay with a raster of 15 mm i can do a conmparison between Wima MKS4 and those... Any recomendations ?

 

[Voodoochile]

I might use a metallized polypro cap, but would not use a polyester cap of any type in that spot. The film/foil polypro caps fit well enough usually (and that is my strong preference), and the difference between them and the metallized polypro caps does not seem too big, though it is notable. As for polyester, I just have never heard one that I care for.

How does it sound to you?

 

[chillysalsa]

I had been wondering about that and came across an interesting comparison suggesting paper in oil is the way to go, for example, Jensen caps.

 

[doobooloo]

Seems like I'll stick with the big bulky Pana P's.

Well now I have $10 worth of pretty box caps with nowhere to go... mmm...

 

[Daroid]

Maybe you could use tantalums instead, i don't know for sure. At least they are much smaller and has a lower lead pitch. Price-wise they are about the same as polypropylene

 

[Nisbeth]

Tants are bad for this application. They should be restricted to PSU's and the like

/U.

 

[SHLim]

Have anyone tried Polyphenylene Sulphide - PPS? Was told that they are very good as bypass.

Sam

 

[jnewman]

Quote:

Originally Posted by SHLim Have anyone tried Polyphenylene Sulphide - PPS? Was told that they are very good as bypass. Sam

I'm using them in my WNA as PSU bypass caps. They seem to perform VERY well.

They're marketed as a almost perfect replacement for the very expensive polycarbonate caps, which I understand have a reputation for responding very crisply and cleanly with very little noise.

I'm using Panasonic ECHS types.

 

[doobooloo]

Interesting... But what about for signal purposes?

 

[jnewman]

Quote:

Originally Posted by doobooloo Interesting... But what about for signal purposes?

I've only really used coupling caps in my most recent amp (WNA with bipolar input opamps) and used Blackgate N bipolars and (soon to be added) Solen SM polypropylene film/foils as output caps. Well, and Pana ECQ's as CMoy input caps. I haven't done all that much experimenting with other signal path caps.

I expect the PPS caps would work well and be very clean and detailed but this is NOT based on personal experience using them in signal positions.

 

[morsel]

Capacitor dielectric dissipation factor (DF), smaller is better:

Polyester (PETP) .5%
Polycarbonate .05%
Polyphenylene sulfide (PPS) .05%
Polystyrene .05-.02%
Polypropylene .025-.01%
Teflon (PTFE) .025-.01%

These numbers were culled from over 100 documents on the web.

 

[doobooloo]

Thanks morsel for the data!

It's interesting though how polystyrene has higher DF than polyprops but still are considered to be sonically superior. Euphonic distortion playing a role here...?

 

[morsel]

I don't recall any sources that suggest polystyrene is better than polypropylene.

Perhaps the most interesting observation is that PPS is comparable to polycarbonate and polystyrene, both of which were popular for audio use but are no longer manufactured.