What the ? - Odd Capacitor Results - diyAudio
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Old 6th August 2013, 01:10 AM   #1
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Default What the ? - Odd Capacitor Results

Hi gang, I'm building a U47 clone and decided to be an audiophool and get some high-end caps.

We have 3 caps: a .01uF V-cap TFTF; a .1uF V-cap OIMP, and a 1uF Mundorf Silver/Gold Oil cap:

Click the image to open in full size.

So I wanted to pre-burn these babies in before installing them in the mic I'm building. I read Jim Williams of Audio Upgrades suggested a 10K square wave at 10V into a 100R resistor. Since some of these caps take hundreds of hours to burn in, and since I'm using 50-year old vacuum tubes that I'd rather not put those kind of hours on, I'm pre-burning them in.

So here's the results of an oscilloscope test. The top image is the square wave input. These are actually 3 different outputs so even though they look identical, I'm including them for honesty's sake:

Click the image to open in full size.

Guys, I'm no EE (my dad is), and perhaps I don't know what the f I'm doing. But can anyone explain why in cat's heaven the V-cap OIMP and the Mundorf are destroying the input signal, and the V-cap TFTF (teflon) are not? Could it have anything to do with the value of the caps...same 10v square wave driving each one.

If the OIMP and the Mundorf really are destroying signals like that, could they be damaged caps, or is this what they actually do to a signal? Why would anyone ever use anything but the teflons then...

Thoughts please? Be kind. I'm no electronics genius.



PS all caps are brand new from the factory. Also if you like GroupDIY I posted it there too.

Last edited by PhrazeMaster; 6th August 2013 at 03:02 PM.
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Old 6th August 2013, 03:21 AM   #2
ArtG is offline ArtG  United States
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Since I'm pretty well entrenched in camp of the people that you told to "go away", and I don't know the exact circuit and conditions that you are using to test your capacitors, I don't feel that I'm qualified to reply.

However... what would be really interesting, would be to see those scope traces under the exact same conditions after hundreds of hours of "burn in".
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Old 6th August 2013, 05:28 AM   #3
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Hi Art, no offense meant...I just get tired of people claiming all 1uF caps sound the same. In any case, I had the same thought, and I'll try to post pix of them after the burn in.

Thanks for chiming in.

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Old 6th August 2013, 07:15 AM   #4
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Originally Posted by PhrazeMaster View Post
But can anyone explain why in cat's heaven the V-cap OIMP and the Mundorf are destroying the input signal, and the V-cap TFTF (teflon) are not?
I understand you are not an EE, or even remotely aware of electrical theory, but still: do you think it's reasonable to compare widely varying capacitances in your setup?

What you get is normal capacitor behaviour. It has nothing to do with the type of dielectric or price.

The burn-in won't change these pics at all.

Last edited by analog_sa; 6th August 2013 at 07:17 AM.
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Old 6th August 2013, 07:33 AM   #5
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Sorry, I'm not "remotely unaware of electrical theory" - I have taken the entire undergrad core in physics including electricity with good grades - 20 yrs ago. I don't appreciate the dig. I understand Ohm's law, and after some posts at groupdiy.com I spent time looking things up. Here's my calcs - go ahead find the errors.

Click the image to open in full size.

Here's the site I found for understanding it:

Series RC Circuits

Please, let's keep this forum in a spirit of fun and learning. I refuse to be afraid to post before spending an hour looking up equations. It's posts like that, that make forums suck.

Maybe it's time to retire.

Night all.
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Old 6th August 2013, 07:42 AM   #6
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FYI: "Burn in" is not a thing, so this process is a waste of your time.
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Old 6th August 2013, 07:42 AM   #7
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Maybe you have the last two film caps facing in the wrong direction. ;-)
Paradise Pre-reg PSU PCBs
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Old 6th August 2013, 07:44 AM   #8
Arno Pf is offline Arno Pf  Netherlands
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Where is the input signal measured (input amp or input test circuit)? What is driving the circuit and with what output impedance?
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Old 6th August 2013, 07:48 AM   #9
Elvee is offline Elvee  Belgium
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This is what you should see, no matter which capacitor you plug in: with this set-up, the cheapest and lousiest mylar will give the same visible result as the most expensive fused silica lab standard:

The variations you observe either mean you're making something completely wrong in your measurement, or all of your boutique caps are complete crap (or both)
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Old 6th August 2013, 08:00 AM   #10
Enzo is offline Enzo  United States
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Relax. You are the one who first said you were no EE, so what are we to assume then? And you are the first one to take a dig at people who think differently in your opening post, so...

IN any case, you present three caps. One is a 0.01uf, one is a 0.1uf, and one is a 1.0uf, at least as far as I can tell from your description. Unless I missed something, why would we expect the three caps to react the same when each is different from its neighbor by a factor of 10 in capacitance?

I suppose your calculations work for your 1uf cap. Now go do them for the other two values. yes, value matters. A good example of mattering is the caps in your speaker crossovers. Change the value, change the frequency.

I don't know those caps, I am not into that, but look up the data sheets on each. Aside from capacitance, you might see what they show for ESR and things like self-inductance.

I think it is dangerous to over-generalize attitudes about caps. It is not black and white. I wouldn't argue against better quality caps sounding better in some way. But then I probably would not agree that $100 caps are better than $10 caps.
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