Help!! Polypropylene capacitors confusion! KP or MKP???

[fotios]

My case it has become a domino. After resolving my query about the Vbe multiplier in a previous thread, it resulted a new problem under the marking of two members for the quality of capacitors that I use in my amplifier sample. They proposed me to improve the quality from MKT (metalized polyester foil) to KP (polypropylene foil). Their remarks are of course reasonable. I have already improved the quality of the rest caps in my module. All electrolytic are now Panasonic ECA type and all ceramic substituted from Cornel-Doubilier silvered mica. In the power supply fortunately from the beginning I have bought caps of Nichicon LS series. The rest remained are: 1) the input cap 22mF electrolytic 2) Some decoupling of 100nF MKT ( polyester metalized ) also in the Zobel and in the bootstrap (speed up) across the Vbe multiplier. One MKT of 33nF across the shared emitter resistor between the drivers. Finally two 47nF MKT in the VI limiter. The input cap will be replaced by a 2,2mF non electrolytic. According the suggestion of "Lumba Ogir" the caps are classified according to their quality as follows: 1) Polystyrene 2) Polypropylene foil (KP) 3) Metalized polypropylene foil (MKP). All the other types are useless in audio devices. I searched thoroughly the sites of WIMA of EPCOS and of Arcotronics and I discovered the following;
For the input 2,2mF there is not available KP type from any company. The only available it is a very big cap of LCR for use in speaker crossovers. All the other companies they offer only MKP type in relatively logical size. For the rest caps of 33nF, 47nF and 100nF because they must be in the range of 160Vac (for safety because the +/-70Vdc = 140Vpp supply level) also they don’t offer KP types (WIMA FKP2) in logical dimensions, instead they offer in the range of 250Vac (WIMA FKP3) with enormous dimensions and thus unusable. After all of these I think to proceed in the MKP types. If any of you have experience of a comparison between the KP and MKP type how much is the loss in sound quality (from my bench tests I can’t find any improvement with my usual test of square waves in input and the scope in output) his opinion will be well appreciated.
Thanks for the help in advance
Fotios

[john curl]

MKP probably means metalized. That means that the metal is sputtered as a thin film on the dielectric. KP probably means film and foil Separate films, and they are somewhat better, especially for high current applications. In your case MKP should work just fine.

[Lumba Ogir]

Hi fotios,

All the other types are useless in audio devices.

I did not say that. Please be careful.
I listed them in order of sound quality (actually the same as increasing dielectric and resistive losses)
Even more accurately: 1. PTFE 2. polystyrene: 3. polypropylene 3. Polycarbonate 4. polyester
Non-metalized film IS better than metalized film.
Now start studying. Apparently, you have a very long way to go.

[fotios]

Originally posted by john curl
In your case MKP should work just fine.

Thanks mr. Curl for this SIMPLE and BRIGHT advice. The ancient Greek said: "As long as better you know a subject so much more simply you can explain it." That is! In eight words inluded the essence of a whole book or if you prefer a pactolus of post replies.
Mr. Curl, as it appears except a designer you are a real craftsman.
Respects
Fotios

[Eric Juaneda]

Hello Fotios,

I think you already read very interesting article about using capacitors in audio. PICKING CAPACITORS

Written by Walter G. Jung and Richard Marsh. The authors would like to acknowledge private discussions with John Curl and J. Peter Moncrieff on the subject of capacitors in audio circuits and how they might influence subjective testing.

Eric

[taj]

All,
Just curious... Would it make sense to use a large crossover style polyprop cap for the input cap by having it interconnect the PCB to the input jack? Its size would be less of a concern.

Lumba,
What is PTFE? Teflon?

..Todd

[peranders]

Originally posted by fotios
...
For the input 2,2mF there is not available KP type from any company....

http://www.elfa.se/elfa-bin/dyndok.p...htm?_65_465_43

[AndrewT]

Hi,
using a big cap to link the input to the PCB makes some sense.
But take care to secure it.
You don't want vibration or movement to fatigue the leads.

[fotios]

Originally posted by peranders



http://www.elfa.se/elfa-bin/dyndok.p...htm?_65_465_43

Thanks Peranders for the link.
I have already resolve my problem by a direct contact with WIMA factory for asking samples. They redirected me in a German distributor which has in stock all the types that i wish. Wima it is a good and helpful company. This German distributor of Wima, it is a big company and undertake only with gross orders, not with a few samples. But under the admonition of WIMA they accepted to send the samples and the aggravation goes to WIMA, that is to say i get the caps finally free of charge. Take into account this. Maybe proved very useful and in you in the future.
As for the capacities that i need for my amp. samples, you may read the values and you understand the difficulty to find these caps in logical dimensions as to be left over space in the PCB to contain the transistors and the resistors! Can you imagine a PCB with caps only?
1) 33nF / 250Vdc (160Vac)
2) 47nF / 250Vdc (160Vac)
3) 100nF / 250Vdc (160Vac)
4) 2,2mF / 100Vdc (63Vac)
The only series offered from WIMA (and from any other company as i think) in logical dimensions are: MKP4 for 2,2mF and MKP2 for the rest.
Another item that may i refer it is: if you want MPC resistors (metal plate cemented non inductive in very low price) for the emitter of your BJT output transistors ask samples from FUTABA ELECTRONICS (SUZHOU) CO., LTD.
www.futaba.com.tw
It is very helpful company and sends from 20 to 30 samples free of charge.

[QSerraTico_Tico]

Originally posted by taj
All,


Lumba,
What is PTFE? Teflon?

..Todd

yep polytetrafluorpolyethylene= Teflon (R)
http://en.wikipedia.org/wiki/Teflon