Exactly What Is A PETP Capacitor?

Grainger49 · 18935

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Offline Grainger49

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on: December 23, 2010, 09:45:23 AM
I have some KKs that are K73-16.  They are PETP, but what is PETP?  And how good is that as a dielectric?

Thanks in advance.


Offline xcortes

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Reply #1 on: December 23, 2010, 10:36:11 AM
PTFE

Xavier Cortes

Offline Grainger49

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Reply #2 on: December 23, 2010, 10:43:19 AM
These don't look like the Russian Teflons, PTFE, they are green on the ends and I believe were sold as PETP.  Sounds like a lot of alphabet soup.


Offline Paul Joppa

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Reply #3 on: December 23, 2010, 11:45:41 AM
From Wikipedia:  "Polyethylene terephthalate (sometimes written poly(ethylene terephthalate)), commonly abbreviated PET, PETE, or the obsolete PETP or PET-P..."  Think Dacron sails and polyester Nehru jackets. Also called Mylar.

Paul Joppa

Offline Grainger49

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Reply #4 on: December 23, 2010, 01:24:13 PM
Thanks, I know PET as the plastic in soda bottles.  Mylar I also know but didn't know they were the same stuff.

Were Nehru jackets Polyester?  (remember them well, didn't have one)

Are they supposed to be good sounding caps?


Offline Jim R.

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Reply #5 on: December 25, 2010, 03:53:36 PM
Mylar is used in many caps, and even sometimes is also found in the paper of some otherwise labeled paper caps.  I believe the Jupiter HT series is actually a paper/mylar blend of some sort, but it is still described as paper.  I believe only the orginal "wax candle" type Jupiters are the only ones that had a pure paper dielectric.  Also, they now say so, but I suspect that the original Audio Note PIOs -- copper, silver and tin -- also had a paper with a certain percentage of mylar in it.  And of course there are dozens of metalized polyester types.  Auricaps, for example.

Have you given them a listen yet?

-- Jim

Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)

Offline Doc B.

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Reply #6 on: December 25, 2010, 05:39:16 PM
I think that Auricaps are metallized polypropylene rather than polyester.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline Grainger49

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Reply #7 on: December 26, 2010, 01:28:28 AM
Jim,

I have used them as power supply bypass only.  I will give them a listen in something soon.

Thanks for the information.  It is encouraging. 


Offline ToolGuyFred

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Reply #8 on: December 27, 2010, 03:27:08 AM
I find that the relative permitivity or dielectric constant is often a fair guide to a material's "goodness" for use in an audio capacitor:

Vacuum1 (by definition)
Air1.0006
PTFE2.1
Polypropylene2.2-2.36
Polystyrene2.4-2.7
PETP3
Polyimide3.4
Paper (unoiled)3.5
Transformer Oil4
Mica3-6
Glass5-10
(Information from Wikipedia, ElectricianEducation.com and Goodfellow.)

Hope this is useful.

John
Amateur Audiophile and Backstreet Boffin.
Original Foreplay with C4S + Sweet Whispers
ParaSEX amps with MQ nickel-cored outputs
Factory-built Lowther Acousta 115s with silver-coiled DX3s, wired in DNM solid-core
KEF active sub (help for the last couple of octaves).
Bottlehead DAC on batteries.

Offline Jim R.

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Reply #9 on: December 27, 2010, 05:17:10 AM
Dan is right, I mistated on he auricaps.

John, thanks for the table.  Don't see cotton, silk, or polycarbonate on there -- there are some new caps coming out with polycarbonate dielectric now, but I have no idea how they sound.

-- Jim

Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)

Offline Grainger49

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Reply #10 on: December 27, 2010, 06:12:54 AM
Fred,

Thanks, I have some air dielectric parallel plate capacitors.  I probably won't try them though. (Picture turned upside down to make more sense)

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi244.photobucket.com%2Falbums%2Fgg7%2FGrainger49%2FIMG_0291.jpg%3Ft%3D1293469920&hash=bb88226d26db973ceb3435c078ce367acddd022a)

Good list!  Funny, it follows much of what I have experienced and heard elsewhere.  My true confusion was not knowing that my new KKs were made of old Nehru Jackets (Dacron/Polyester).
« Last Edit: December 27, 2010, 01:11:26 PM by Grainger49 »


Offline ToolGuyFred

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Reply #11 on: December 27, 2010, 11:45:16 AM
Quote from: jrebman on December 27, 2010, 05:17:10 AM
John, thanks for the table.  Don't see cotton, silk, or polycarbonate on there -- there are some new caps coming out with polycarbonate dielectric now, but I have no idea how they sound.
Can't find any values for silk.

Polycarbonate2.9
Cotton1.3-1.4

The polycarbonate & foil caps I have heard were OK but only available in low values.
Cotton will only maintain this value if kept bone dry - some sort of oil or resin would keep the moisture out - but I suspect that would seriously impact the dielectric constant.

John
Amateur Audiophile and Backstreet Boffin.
Original Foreplay with C4S + Sweet Whispers
ParaSEX amps with MQ nickel-cored outputs
Factory-built Lowther Acousta 115s with silver-coiled DX3s, wired in DNM solid-core
KEF active sub (help for the last couple of octaves).
Bottlehead DAC on batteries.

Offline Jim R.

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Reply #12 on: December 27, 2010, 03:35:35 PM
John,

Thanks, and I am also looking at this from a wire insulation perspective as well.

Lie Grainger, most of this agrees with what I've heard (though have not heard any polycarbonate caps myself yet)  That said, I'm not a huge fan of teflon on wire, but in caps, I do mostly like it.

-- Jim

Jim Rebman -- recovering audiophile

Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).

s.e.x. 2.1 under construction.  Want list: Stereomour II

All ICs homemade (speaker and power next)

Offline Dyna Saur

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Reply #13 on: January 05, 2011, 03:24:10 PM
Then there are the caps which are not really that  which they appear to be:

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.pastisch.se%2Ffaktiskt%2F20071207-214523.jpg&hash=6693de5e604505a91f32d68886333faf1a019854)

Saw this one  over at the www.diytube.com website

/ed B in NC


ed brown

Offline Paul Joppa

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Reply #14 on: January 05, 2011, 05:03:51 PM
Yow! That's scary.

Speaking of scary, thanks for the link - I didn't know of that site. Under SC35 there's a thread on standby switches in the center tap of the power transformer - exactly what I've been telling people for years based on theory, and nobody every buys it. But it's true nonetheless - switching high voltage DC will destroy switches. Nice to see that experience nears out the theory!

Paul Joppa

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