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Hi Guys
I'm thinking about building a set of these. Having looked at the price of the silver mica capacitors, for the larger value it will work out quite expensive. I need to build 6 and therefore require 18 of the 3300pf. I do have access to Wima FKP1s (which are polypropelene with metal foil) at a good price and was wondering if these would be suitable.
Would it be ok to mix the types of capacitor eg metallised polyester film and FKP1s?
Your thoughts and comments are welcomed.
Many thanks
Follow Ups:
Al Sekela was the first to publish and develop these on this board. Chris Da Costa coined the HRSF and published the first instructions with pix here on the board.
Al always guided me toward the silver micas for this particular application (metal foil for the AC version of R-C network filtering). Al did some testing of cap types before settling on this and he never did take it to any other type. I've just stuck with the silver micas.
I'd suggest you bite the bullet. They do sound good and improve the system. I'd recommend against mixing cap types in any case.
We got ours cheaply through a Bay Area dealer called Halted Specialties (or HSC), which does have a website. Try contacting them to see if you can get a deal on the silver micas in the size you need.
Hi
The cost of a 3600 pf sliver mica from a well known dealer here in the UK is about $7.50. As you can see quite a cost. I am aware that you can probably buy them a hell of a lot cheaper in the US. I may just have to do some research, although it is usually the postage and packing that is expensive. Hence the question about using alternantives.
Many thanks
Didn't realize you were in the UK.
The HRSF is a finely finished version of what Al experimented with more crudely in stages. You can do that same experimentation on your own and decide for yourself.
Here's the best way to test out different caps in this application: Don't solder, just wirenut the components together. Switch out cap types and see what sounds best. Then when settled on your best shot that pleases you, solder up the final job.
Chris' construction instructions are excellent and will produce excellent final products if you do them right. But the R-Cs work as first drafts too.
BTW, the grounded Ti-Shield versions really are the best, IME.
Wima Polypropylene FKs are fine. Silver Micas have good or bad versions, depending on how leads are attached and on whether these are magnetic.
I would never use Ceramics, even COGs for speaker filters. You'll have a job finding tightly toleranced ones anyway.
"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
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
I recommend that you go with COG monolithic ceramics. They are very stable and have low dissipation and ESR. I would use the 100V one's in a 1206 SMT package for low stray inductance and series resistance while being easier to solder to than 0805's. Keep the resistor leads as short as possible to maximize the self-resonant frequency.
You can get then at Digi-Key for 50c ea.
http://www.digikey.com/product-detail/en/12061A332JAT2A/478-1453-1-ND/564485
Don't use film caps, they have tons more self inductance.
Have fun, Rick
What are these? Are you making reference to the English College?
A little more info, please as to what is HRSCF.
DaveT
Hi
HRSF means High Resolution Speaker Cable Filter. It's been discussed in thr forum although perhaps for not some time. Below is an extract from a publication by Christopher da Costa:
"The High Resolution Speaker Cable Filter or (HRSCF) is a Resistor and Capacitor filter network, also known as a R-C Network. This particular R-C Network is designed to filter out ultra high frequency electronic noises being picked up by, and is riding on your speaker cables. The noise that the HRSCF is filtering out as I understand it, is ultra sonic electronic noises that is outside our hearing range. These
electronic noises are created by our electronics, and all the pollution that now is everyday in our society. Our speaker cables act like an antenna for these electronic noises. The electronic noises hide or mask information that is intended for your speakers to reproduce."
Hope that helps
Regards
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