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Old 17th February 2013, 12:55 AM   #1
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Default Capacitor dielectric - high impedance headphones

I recently built the 'Broskie Unbalancer' for use as a preamp, however the vrms of my source is strong enough to power my amplifier so I have removed it from the chain and plan to use it as a headphone amplifier instead.

I am using some Beyerdynamic DT880, which are high impedance @ 600R.
I notice on page 7 of Broskie's documentation he states:

"which with a 1F coupling capacitor will give a -3dB frequency of 11.5Hz. If the BCF is used to drive 300-ohm headphones, a job that the BCF is amazingly good at, at least a 30F coupling capacitor is needed"

Presumably I can get by with around 20F, but there certainly isn't enough space in the chassis/casing or on the board for a film/PIO cap - can anyone suggest another suitable type of capacitor?
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Old 17th February 2013, 01:22 AM   #2
jcx is offline jcx  United States
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I believe even polyester/Mylar measured better than Electrolytics in Bateman's tests

but you could get 10x value Al electros for a fraction of the price
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Old 17th February 2013, 09:24 AM   #3
hpeter is offline hpeter  Europe
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Quote:
Originally Posted by jcx View Post
I believe even polyester/Mylar measured better than Electrolytics in Bateman's tests

but you could get 10x value Al electros for a fraction of the price
afaik polyester are not recommended for audio at all, polypropylene are better
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Old 17th February 2013, 09:32 AM   #4
tinitus is offline tinitus  Europe
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.... polypropylene are better
ahh... well if nothing else, at least it have been a very reliable goldmine...and as it seems, will go on forever and never dry out

but if they really put their hart into making better polyester caps, I bet they would be the top and that btw was not ironic or a joke

might be more a matter of production quality ...things like clean materials etc
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Old 17th February 2013, 10:28 AM   #5
Pano is offline Pano  United States
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You need a high voltage electrolytic here. 30uF minimum, 250V. Not much way around that. Look for a good one and bypass it with a film cap.
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Old 17th February 2013, 10:37 AM   #6
hpeter is offline hpeter  Europe
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Quote:
Originally Posted by tinitus View Post
ahh... well if nothing else, at least it have been a very reliable goldmine...and as it seems, will go on forever and never dry out

but if they really put their hart into making better polyester caps, I bet they would be the top and that btw was not ironic or a joke

might be more a matter of production quality ...things like clean materials etc
well, it could be only some opinions from internets, but i looked in families of products from WIMA
some PP caps are audio rated, but none of their PE
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Old 17th February 2013, 10:43 AM   #7
hpeter is offline hpeter  Europe
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https://www.distrelec.sk/vrstvov%C3%...-ru-fra/822419
look in datasheet
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Old 17th February 2013, 10:47 AM   #8
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ok thanks, I built this board as a 'paint by numbers' project so don't really know what 'bypass' here means - are you suggesting just soldering a 30uf capacitor on top of the current film cap (0.68uf pio), piggyback style?
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Old 17th February 2013, 10:51 AM   #9
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Bypass with film cap with different structure is not good idea for quality of sound for HF and MFreq....Main output cap must be only one and with High quality.
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Old 17th February 2013, 01:49 PM   #10
DF96 is offline DF96  England
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If the capacitor has a sufficiently high value that it has low signal voltage across it, even at low frequencies, then it can't generate much distortion no matter how bad a cap it is. 100uF electrolytic would do. You can bypass it if you think this will help.
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