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Lurcher300b
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Re: PFM

Unread post by Lurcher300b » Sun Apr 15, 2018 10:10 am

Lindsayt wrote:
Sun Apr 15, 2018 9:19 am
So this is bullshit?
https://electronics.stackexchange.com/q ... le_rich_qa
And there's something up with the measurements in that pfm thread, where 4700uf caps are measured at 8000uf?
I think you need to read the first reply to that thread.

"How do you know they increased with age, and weren't just big all along? Capacitance tolerances for electrolytic capacitors are quite often -10%/+80% or even worse. "

I am with Dave on this one.

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terrybooth
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Re: PFM

Unread post by terrybooth » Sun Apr 15, 2018 10:18 am

Lurcher300b wrote:
Sun Apr 15, 2018 10:10 am
Lindsayt wrote:
Sun Apr 15, 2018 9:19 am
So this is bullshit?
https://electronics.stackexchange.com/q ... le_rich_qa
And there's something up with the measurements in that pfm thread, where 4700uf caps are measured at 8000uf?
I think you need to read the first reply to that thread.

"How do you know they increased with age, and weren't just big all along? Capacitance tolerances for electrolytic capacitors are quite often -10%/+80% or even worse. "

I am with Dave on this one.
But is that last post correct? Which I read as a need to size capacitors to the expected load to ensure that they are loaded enough but not overloaded? (Obviously, I know nothing about this - just following the logic of the arguments). If it is, then the conclusion for me is that each capacitor would need to be measured before building it in to ensure that the capacitance is in the correct range. Even then, there is probably an argument that this really doesn't matter in a particular circuit so far as sound quality is concerned. If this latter is correct it point to people (like me) ceasing on a particular point and not understanding the bigger picture.
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Lurcher300b
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Re: PFM

Unread post by Lurcher300b » Sun Apr 15, 2018 10:41 am

Even then, there is probably an argument that this really doesn't matter in a particular circuit so far as sound quality is concerned. If this latter is correct it point to people (like me) ceasing on a particular point and not understanding the bigger picture.
Yep, the very fact that you are using a electrolytic cap means the actual value doesn’t matter within the sample tolerances. If you needed accuracy, you would use a different type of capacitor. I am afraid it seems to be part of the OCD of the typical HiFi User to assume that everything matter, it doesn't, only the things that matter matter :-). The trick is to find which those mattering things are.

Vinyl-ant
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Re: PFM

Unread post by Vinyl-ant » Sun Apr 15, 2018 11:09 am

How was it even measured? If it was measured by using the pcb tracks, it could be in parallel with another cap of the same size.
There is no way to confirm the reading is not false. Lcr meter or the capacitance function on a normal dmm? Who knows? I find it hard to believe that a cap can be that far away from its quoted figure
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Daniel Quinn
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Re: PFM

Unread post by Daniel Quinn » Sun Apr 15, 2018 11:26 am

That would of course mean that builders of a certain nirvana based Phono stage are deluded.
Even a stroke didn't result in me liking AOS

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Lindsayt
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Re: PFM

Unread post by Lindsayt » Sun Apr 15, 2018 12:53 pm

Lurcher300b wrote:
Sun Apr 15, 2018 10:10 am
Lindsayt wrote:
Sun Apr 15, 2018 9:19 am
So this is bullshit?
https://electronics.stackexchange.com/q ... le_rich_qa
And there's something up with the measurements in that pfm thread, where 4700uf caps are measured at 8000uf?
I think you need to read the first reply to that thread.

"How do you know they increased with age, and weren't just big all along? Capacitance tolerances for electrolytic capacitors are quite often -10%/+80% or even worse. "

I am with Dave on this one.
Yep, I'm happy to take your and Dave's advice on this one too.

Geoff.R.G
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Re: PFM

Unread post by Geoff.R.G » Sun Apr 15, 2018 1:17 pm

Given that the capacitance of a device is affected by the overlapping surface area, the dielectric constant of the material separating the plates and the gap between them it is very hard to see how the value will change with age. The overlapping surface area is fixed once the capacitor is manufactured and the distance between the plates likewise. The dielectric constant of the separator could change if the material deteriorates but remember that it is effectively sealed off from the environment. An.electrolytic capacitor will have an electrolyte forming one conductor and this can, in theory, be lost but such loss would reduce the capacitance and would, one hopes, be obvious. Unfortunately loss of electrolyte isn't a common failure mode in electrolytic capacitors.

In simple terms, capacitors cannot increase in capacitance value as they age.

keepitsimplestupid
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Re: PFM

Unread post by keepitsimplestupid » Sun Apr 15, 2018 4:09 pm

Daniel Quinn wrote:
Sun Apr 15, 2018 11:26 am
That would of course mean that builders of a certain nirvana based Phono stage are deluded.
Please explain your post. I'm sure myself and all the other builders of the Paradise would love to benefit from your experience and technical expertise in this area.

Is it that you don't think that careful matching of input stage transistors in a zero feedback amp proving 1500x gain is pointless, or that the swap to a later revision of the PSU board with an extra 3rd cap in the smoothing bank, taking a C-L-C-R filter to a C-L-C-R-C filter is pointless?
Last edited by keepitsimplestupid on Sun Apr 15, 2018 4:12 pm, edited 1 time in total.

Daniel Quinn
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Re: PFM

Unread post by Daniel Quinn » Sun Apr 15, 2018 4:11 pm

It's not my expertise.

You have altered your post to indicate that you do not only measure capacitors. The logical inferences I drew are of course related to capacitors only .

Furthermore they are just that logical inference not opinion.
Last edited by Daniel Quinn on Sun Apr 15, 2018 4:21 pm, edited 1 time in total.
Even a stroke didn't result in me liking AOS

keepitsimplestupid
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Re: PFM

Unread post by keepitsimplestupid » Sun Apr 15, 2018 4:16 pm

I take it from that that you are implying that Nick's comment somehow relates to the value of the precision of parts matching in the Paradise.

Perhaps you've made a mistake in your attribution ?

Perhaps you'd like to explain what you meant, then someone with the requisite knowledge and experience can explain it to you. And then maybe you'd choose to remove your snidey little remark, because then you'd know how embarrassingly wrong it was.
Last edited by keepitsimplestupid on Sun Apr 15, 2018 4:19 pm, edited 1 time in total.

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