Posted on Saturday, 24th April 2010 by Auw Jimmy
I just got my Oscilloscope, so I can play more fun with my DIY stuff. Ok, let’s start with some basic “game”, to find the inner and outer foil of a capacitor.
Basically, most of the capacitor, has what we call the inner foil and outer foil. Because, most of capacitor’s construction is based on the winding of paper or other conductor (silver, copper, gold, etc), so we will have a start position (the inner foil) and the finish position (the outer foil).
Although for the film type capacitor, it’s just fine to connect positive or negative to the inner or outer foil. But due to some reason, it’s preferable to connect the outer foil to negative side or to the “nearest” negative side (input side on coupling application).
Why? Because the outer foil will catch the outside interferences. So better if you can put this outer foil to the place nearest to ground or negative pole. So it could completely transfer those unwanted noise faster to the place where it should belong – the ground.
Some capacitor like Audio Note, Jensen, Auricap, Hovland, VCap, etc usually marks their capacitor with different color lead or print some black line to mark the negative side or input in the coupling application. Some other popular capacitor, like Mundorf, doesn’t seem to care about this, means no marks at all. So you got to check it by your own. Other capacitor like Duelund, which uses the Stacked Foil design, I believe doesn’t have any polarity (it’s not winded, but stacked).
How to do the test with Oscilloscope? Simple by testing both leads, and give some “interference” outside the capacitor (touch by hand or put some electric field interference e.g. high voltage cable, etc). The side with higher noise, means the outer foil.
Below are some picture from my own measurement on some capacitors.
Audio Note Oil Filled Mylar Capacitor. The black line marking on the capacitor’s body means the negative or input side. We can see the noise is quite big if we put the positive probe on the side which has black line marking.
Lower noise if we put on the probe on the opposite way.
Mundorf Supreme Capacitor doesn’t have marking, so you must measure one by one to confirm.
For sure, lower noise if we place the probe on the opposite way.
Jensen Copper Foil Paper Tube puts same black marking as Audio Note. And my observation also confirms the black marking side is the outer foil or input side.
Lower noise for sure, if you test on the opposite way.
Old Auricap, black lead means the input side or negative. I also confirm this to be true.
Lower noise if we try testing the red lead.
That’s all my first game with oscilloscope. Will observe what I can do more with my new Oscilloscope in the future 
Tags: Capacitor, measurement, oscilloscope
Posted in DIY Audio | Comments (36)
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Mundorf MSolder Supreme Silver / Gold
April 25th, 2010 at 19:11
osiloskopnya keren…. beli berapa bro??
April 25th, 2010 at 20:35
Saya beli dari luar, kalo di sini mungkin bisa 5jt-an.
Thanks.
April 26th, 2010 at 23:14
lumayan juga yah.. harganya. kapan2 di review bro osiloskopnya
April 27th, 2010 at 14:12
ko jimmy mau nanya neee di daerah mana ya di negara hongkong dan singapore buat belanja komponen ( resistor dan elco )yg murah dan lengkap
April 27th, 2010 at 23:18
Waduh kurang tahu lokasi detailnya bro. Saya lebih sering belanja online sih.
Thanks.
April 28th, 2010 at 04:31
belanja on line nya via fb or?????bro tolong dunk info nya belanja on line nya dimana aja.tx
April 28th, 2010 at 11:32
Ya banyak bro. Bisa di partconnexion, percyaudio, ebay, angelainstrument, diyhifisupply, thl-audio, etc.
Kalo FB ga ngerti deh apaan tuh.
Thanks.
April 28th, 2010 at 12:51
Mantaf Pak Jimmy, nanti saya check JPT saya di rumah, apakah ‘arah’ nya sudah bener hehe.. btw, kalo untuk fungsi bypass, apakah perlu arah yang benar juga?
Salam,
Arie
April 28th, 2010 at 21:31
Silakan dicoba bolak-balik Om Arie hehehe…
April 30th, 2010 at 07:25
Very interesting to see the difference on an oscilloscope. Very worthwhile post, thank you!
I read that there is also a sound difference depending on which end of a resister is toward the input or negative. It would be interesting to know if that could be sorted out with an oscilloscope rather than a listening test which takes much longer. Or do you know another shortcut?
Dan
April 30th, 2010 at 12:53
Alatnya besar gak pak Jimmy?
Bawa donk ke padepokan hehe…
salam,
Arie
April 30th, 2010 at 22:55
Hmm, your conclusions contradict what Mundorf told me about the Supreme caps when I asked them how to tell which side was the outer foil:
“Very simple…just follow the imprint’s reading direction. It leads to the lead connected to the outer foil.
Thank you for using our caps. Enjoy the music!
Best regards,
Norbert Mundorf”
May 2nd, 2010 at 23:59
[...] reading my article about finding out capacitor inner-outer foil, some of my readers asked me to do the similar test on the resistor. Well, technically speaker, [...]
May 3rd, 2010 at 20:37
Hi Dan,
Please check my new post.
Thanks.
May 3rd, 2010 at 20:37
Bisa diatur itu Om Arie hehehe.
Thanks.
May 3rd, 2010 at 20:38
Well, I believe the real measurement than what they said.
They could be wrong, accidentally off course, not in purpose, but the machine will tell you the truth.
Thanks.
May 11th, 2010 at 20:40
Hi Jimmy and thanks for the post!
Have you tried testing multiple Mundorfs to see if the shield orientation is the same or random with respect to the writing on the cap?
May 14th, 2010 at 20:29
Hi Armand,
Will do, later. I have some Mundorf on stock.
Thanks.
June 21st, 2010 at 21:21
[...] Before plugging the capacitor, as usual, I checked the capacitor polarity. For you who wanted to learn more, you might be interested to check here. [...]
September 12th, 2010 at 04:10
I tested about 20 Mundorf Supreme caps, and only one tested reverse of the others. The input is usually the end with the M in Mundorf.
October 6th, 2010 at 22:54
I reversed the Mundorf Silver/Gold couplers in my Cary power amp according to your findings (I don’t have a scope any longer to check caps individually) and I’m convinced the background is quieter. More importantly, a slight brightness/hardness disappeared. I wonder how these unknown polarity issues might have influenced the outcome of cap comparisons I’ve read recently on the web?
October 6th, 2010 at 23:23
Hi Armand,
Glad if you get better result.
I don’t have any comment about the others comparison.
Thanks.
October 21st, 2010 at 21:51
wow..good job. would love to test my caps too. ur oscilloscope looks damn high end. not the old school CRT screen.
what brand is this? agilent..
how much did you get it for?
any idea where i can order it
thanks
October 21st, 2010 at 23:57
Hi,
This is “cheap” one, named Rigol. Cant afford Agilent…
You can search online to get yourself one.
thanks.
October 25th, 2010 at 15:31
so if the outer foil(has higher noise), we use
1. input coupling at the outer foil
2. passive xover input at inner foil
correct?
thanks
October 26th, 2010 at 00:42
I think for #2, we still use outer foil as input.
Thanks.
October 26th, 2010 at 00:48
got a reply from Jensen Capacitors
“Black marking is low voltage side” – jensen
“thanks for the reply.
so if its using for signal coupling, then the black marking is the input
But if use for speakers passive as a bypass, then black marking its the output.
correct?” me
“yes” -jensen
*kind of confuse here..
October 26th, 2010 at 09:29
Hi Borgs,
Please verify your application. For speaker in passive, did you configure in series or parallel? You are talking about “bypass” (or decoupling), so we assume you are configuring the caps in parallel configuration. So the black marking will go to the negative side or output. But if you are configuring the caps in series (or coupling, example as 6dB HPF), then the caps black marking should go as input.
Eventually, you can try which side works best for your. All we are talking about is just good in theory.
Thanks.
February 6th, 2011 at 23:25
Jimmy,
In checking the capacitors for the outer foil, what settings do you use on your scope? I’ve had some success in doing this with small value caps (less than 1uF), but do not see much noise difference in higher values. Your display seems to be very clear in showing high and low noise differences, regardless of the value.
Thanks,
Roman
February 7th, 2011 at 09:08
Hi Roman,
Just use the lowest mV setting available, on my scope around 5mV (IIRC).
Thanks.
August 29th, 2011 at 11:37
Roman, a friend of mine and I had the same problem. I wish I could figure this out. I know that having the caps in the “wrong” direction can affect the sound negatively – I accidentally did it in a speaker crossover with auricaps. (They’re marked)
October 3rd, 2011 at 10:44
Mundorf told me the same thing.. read from left to right (+) to (-)
October 3rd, 2011 at 12:55
Jimmy it is stated,
But due to some reason, it’s preferable to connect the outer foil to negative side or to the “nearest” negative side (input side on coupling application).
Then it’s stated,
Jensen Copper Foil Paper Tube puts same black marking as Audio Note. And my observation also confirms the black marking side is the >outer foil or input side<.
When you say 'input side' , what do you mean by this if this is the outer foil side?
I am of the understanding that the 'input side' would be the 'inner side of the cap (+)' and the output would be the outer foil side (-) ???…
Any info appreciated…Thanks
October 3rd, 2011 at 15:53
Hi Ray,
Theoritically, input side in coupling = outer foil of the capacitor = black marking (if any) = negative side in power supply.
But the call is yours
Thanks.
December 13th, 2011 at 22:45
Jimmy,
Do you have repeated your Oscilloscope session after 100 up to 150 hours of break-in? I wonder if the results are the same. I think that capacitors have the mobility to change to the correct direction.
Please inform me if you have repeated the sesion and I am looking out to the results. Good luck with your site which I try to follow. Thanks for the interesting subjects.
with my best regards, ton.
December 13th, 2011 at 23:22
Hi Ton,
The inner and outer foil are physically there. So this will not change (and you cant change also). Dont get yourself confused with cable orientation which happens in ‘sub-atomic’ level – which somehow could be changed.
Thanks.