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Old 10th May 2009, 09:30 PM   #1
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Default Input Capacitor

Hi All,

I was trying to find a good capacitor and available for DC blocking/input.

Has anyone ever tried this one:

http://onecall.farnell.com/ampohm-wo...00v/dp/1636701

It's quite pricy and i was wondering about two things:

1. Is it worth it?
2. With such huge size you got a long signal path, isn't that going to affect the signal more than a small MKT?
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Old 10th May 2009, 09:59 PM   #2
Atilla is offline Atilla  Norway
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This is a paper in oil cap, they tend to be rather big. It's also rated for 300V, which is, well, an overkill.

I think there are smaller, cheaper and better caps you could put in your signal path.
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Old 10th May 2009, 10:10 PM   #3
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Atilla thanks for the reply, which brings me to another question

What voltage rating should this caps have (input signal)? I've seen threads in here where people are using such high voltages, up to 300V or even more and never quite understood the reason. The actual voltage across the cap will be almost zero so what's the point of high voltage rating?

Also has anyone tried instead of these polyester, polypropylene, paper etc. caps to use multiple smt ceramic ones in parallel? And if so is this approach any good?

Cheers
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Old 10th May 2009, 10:22 PM   #4
Mr Evil is offline Mr Evil  United Kingdom
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Exotic capacitors are a waste in my opinion. If you want something nice, try polypropylene. They are much cheaper and much smaller. They are still large, but you can actually fit them into circuits rather than trying to fit the circuit around the capacitor.
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Old 11th May 2009, 05:47 AM   #5
Stream is offline Stream  Russian Federation
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Quote:
Originally posted by Mr Evil
try polypropylene.
It's not polypropylene, it is polyester... Polypropylene is much bigger, more expensive and "sounds better"

otherside , I can recommend You polypropylene caps made by Icel.
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Old 11th May 2009, 11:48 AM   #6
Mr Evil is offline Mr Evil  United Kingdom
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Oops, yes those are polyester. Polyester has a higher dielectric absorbtion, but you won't hear that. Anyway, let's try that again: Polypropylene.
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Old 11th May 2009, 12:43 PM   #7
Atilla is offline Atilla  Norway
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I'd say go for a decent brand polyprop. People would put anything in their signal path, but I think I'm deaf and sane enough not to find enormous difference, unless they do it *wrong*.

A few searches through those forums will give you a bunch of nice and sane suggestions about what to use. You might also be interested in checking out Tangent's article on input caps here - http://tangentsoft.net/audio/input-cap.html
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Old 11th May 2009, 01:33 PM   #8
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Thanks for your suggestions guys.

I've certainly heard the difference between an electrolytic and polyester, now i've never tried polypropylene before so i don't know how different would sound.

I'll try out a few for sure. But to get back to the original question about this huge paper in oil cap, has anyone tried it? not the specific ones but any with such dielectric?

I have to say i'm tempted, and since i'm planning a couple of new designs i don't have any space concerns at the moment. I'm just curious to know if forking over 70 for them will make me "eat my hat" :-)

Cheers
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Old 11th May 2009, 01:35 PM   #9
Puffin is offline Puffin  United Kingdom
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I am using Ampohm Polypropylene in my Gainclone monobocks. I sourced these from a company whose name escapes me, but their details should be found on www.audiojumble.co.uk.

They normally have a stall at the audiojumbles and their prices are very good. I think mine are 3.3uf and were about a fiver each.

Much better sound than ICW polyprops (IMO)

Here is the link :-http://www.audiocap.co.uk/special-offers-56-c.asp
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Old 11th May 2009, 02:19 PM   #10
Atilla is offline Atilla  Norway
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I don't know, 70 for one input capacitor sounds a little bit of a scary price. I can't guarantee any hat-eating, unless it's related to the fact that you just purchased a gigantic cap for a ludicrous price, that does nothing special in the application it's being put in.

I do know I've seen people report on similar caps, paper-in-oil, beeswax, and say good things about them, but all in all they were a little ... smaller.

I'll try beeswax, just for fun, some day

Oh and the link above has some caps with 1% tolerances. I'd be more interested in getting 2(or any number) of low-tolerance caps with good ratings, than putting 2 obscure 10% to 15% tolerance caps in the different channels. A worst-case scenario could end up with quite mismatched channels, after all.
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