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In Reply to: RE: HRSCF posted by fmak on June 04, 2012 at 22:13:00
"I would never use Ceramics, even COGs for speaker filters."
Why?
"You'll have a job finding tightly toleranced ones anyway. "
Tolerances are no problem, 5% is plenty for a low Q noise damper.
Rick
Follow Ups:
The filter is for LSs and Mains.
It is obvious that 100V ceramics are not suitable for mains; they are not suitable for high power amps either.
It is also obvious, at least to me, that one does not want to make up a PCB for lead free miniature components.
There is no problem in using polypropylene or silver mica caps for audio frequency use as filters; we are not talking about inductance effects which must be consdidered in digital signal applications.
"It is obvious that 100V ceramics are not suitable for mains;"
No, they are a little shy, of course if you plug your speakers into the mains that's probably the least of your problems.
"they are not suitable for high power amps either."
Let's see what a 100V capacitor is good for at the speaker...
Maximum allowable cap voltage: 100Vpk*.707=70.7Vrms.
Maximum RMS power amp limit due to cap.= 70.7^2/8ohms= 625W.
Probably not too risky.
"There is no problem in using polypropylene or silver mica caps for audio frequency use as filters; we are not talking about inductance effects which must be consdidered in digital signal applications."
Let's see how that stands up...
Impedance of 3,300pF@20KhZ= 1/wC =2410ohms
That's about 1/300 of the speaker impedance. If these things are going to help anything it's gonna be at RF and the inductance will likely matter.
BTW, silver micas are fine at RF, films not so much...
Regards, Rick
These filters are used for both mains and speakers. There are many many 230V countries.
Ever heard of dynamic/instantaneous power when driving speakers?
"These filters are used for both mains and speakers."
Not according to the definition given by one of the posters: "HRSF means High Resolution Speaker Cable Filter.".
"Ever heard of dynamic/instantaneous power when driving speakers?"
Sure, but it doesn't matter to an external network. It only cares about what it sees at it's terminals, not about what the speaker is up to. If you bottom it out there might be enough di/dt to generate a glitch but it should be fast enough for a lot of it to appear across the resistor.
But if you think it's a big deal then for a buck-ten you can buy 1.5 KV ones and they come in a larger package that's easier to solder to. It would be a comfort to know that if you happen to plug your speakers into the wall that your network will still be just fine, even if you are of the 220V persuasion!
BTW, as you probably noticed I had a typo (heado?) in my previous post. I meant to say that the network had 300 times the impedance of the speaker, not it's inverse.
Rick
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