I have bought these parst surplus at Pollin.de, and according to their list they were MKP, i.e. metallized polypropylen foil. They don't look like one of the classic brands of polyprop caps like Siemens, Roederstein, Wima. I have seen similar devices on the servo board of a CDM4 Philips CD pickup, which would lead me to suspect they are ordinary MKP, i.e. polyester.
I am not sure about their construction, either. They are evidently rolled film, but the wires may be be stuck into the roll like older polystyrene caps, or they may be schooped to the sides.
I am not sure about their construction, either. They are evidently rolled film, but the wires may be be stuck into the roll like older polystyrene caps, or they may be schooped to the sides.
Attachments
Hi Elso,
do you happen to know the brand or have you ever bought them?
I have taken the 18 nF apart. It's a flat roll with the wires stuck into the middle. It contains a metal foil, so it would have to be FKT or FKP. The plastic foil is very thin, stiff and has a silverish sheen which may be residual aluminum or be due to the fact that it actually consists of at least three layers. I have no idea whether they rolled three foils on top of each other or whether the material simply splits like mica.
Is there a test for polyester vs. polyprop? I seem to remember that polyprop is dificult to glue.
Regards,
Eric
do you happen to know the brand or have you ever bought them?
I have taken the 18 nF apart. It's a flat roll with the wires stuck into the middle. It contains a metal foil, so it would have to be FKT or FKP. The plastic foil is very thin, stiff and has a silverish sheen which may be residual aluminum or be due to the fact that it actually consists of at least three layers. I have no idea whether they rolled three foils on top of each other or whether the material simply splits like mica.
Is there a test for polyester vs. polyprop? I seem to remember that polyprop is dificult to glue.
Regards,
Eric
Have a look at http://www.madisound.com/sale.html
There are two caps the same color as mine. One is supposed to be polyprop, the other mylar (=polyester).
There are two caps the same color as mine. One is supposed to be polyprop, the other mylar (=polyester).
Mylar or Polyprop?
Hi Eric,
Yes I admit it is confusing.
What you can do is, if you have available a capacitor tester, is this:
I take my daughters hairdryer and heat up the cap observing the meter.
Polyprop has a negative TC so the capacity decreases on heating.
Polyester or Mylar has a positive TC so the capacity increases on heating.
Polycarbonate has a small negative TC and remains fairly constant. Hope this helps!
Hi Eric,
Yes I admit it is confusing.
What you can do is, if you have available a capacitor tester, is this:
I take my daughters hairdryer and heat up the cap observing the meter.
Polyprop has a negative TC so the capacity decreases on heating.
Polyester or Mylar has a positive TC so the capacity increases on heating.
Polycarbonate has a small negative TC and remains fairly constant. Hope this helps!
All shall be revealed......
TC is temperature coefficient.
Read the following as an intro to caps for audio:
http://www.capacitors.com/pickcap/pickcap.htm
http://www.chipcenter.com/eexpert/akruger/akruger017.html
http://www.evox-rifa.com/cap_catalog/p4-2/geninfor.pdf
Bricolo said:
TC is temperature coefficient.
Read the following as an intro to caps for audio:
http://www.capacitors.com/pickcap/pickcap.htm
http://www.chipcenter.com/eexpert/akruger/akruger017.html
http://www.evox-rifa.com/cap_catalog/p4-2/geninfor.pdf
Different kinds of plastic films have different properties. Sorta like different grades of iron, ferrite etc in transformers.Bricolo said:
Some are dirt cheap.
Some make lots of capacitance per volume.
Some are very stable with temperature.
Some don't get hot at high currents and high frequencies.
Some are just plain unusual and expensive so you can kid yourself how much better the sound is with them.
article about caps
While we're at capacitors. There was an interesting series in Electronics World about capacitors by Cyril Bateman. It was in three parts around the end of the last year and the title was Capacitor Sound if I recall it correctly.
Could anyone help me to read the whole series by scanning in the original? I found only everyone referring to it on the net but I don't seem to get hold of the article.
TIA, regards
monguz
While we're at capacitors. There was an interesting series in Electronics World about capacitors by Cyril Bateman. It was in three parts around the end of the last year and the title was Capacitor Sound if I recall it correctly.
Could anyone help me to read the whole series by scanning in the original? I found only everyone referring to it on the net but I don't seem to get hold of the article.
TIA, regards
monguz
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