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People seem to like a zobel across the speaker terminals. Awe-d recommends .01uf and 10ohms. Some like .1?? I have a 8 ohm speaker. I'm assuming that since the .01 is common this presents no problem to the amp. Any input on what would be optimal and safe? Thanks, Tweaker
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There's been lots of discussion and experimentation regarding these R-C filters on AA and elsewhere...for many years. The most ardent proponent I can think of was the late (great) Al Sekala. He was a firm believer in the value of these filters in reducing the effects of rfi and other amplifier/cable/speaker interface related "problems". Jon Risch has also posted on the subject and you might find of interest/help:
In this article JR is recommending very different values and the high grade ceramic caps designed for rf. Also different values for different types of equipment. ?? T
Here's a a post by AS. There are lots more.
For I/C's..right?
Please see my post below in response to Cougar on your thread. You could also look up "Zobel network" in Wikipedia or wherever. However, no matter what you call it, an RF filter at the speaker terminals, a la the Walker Audio High Definition Links, has seemed to make my own speakers sound better.
What exactly is a zobel network across your speaker terminals? How does it make your speakers sound better? How do you do it? Thanks!!
Further, a Zobel network in audio systems is usually implemented at the amplifier output terminals, rather than at the speakers, although I suppose it could be done either way, but the calculation would be different, because the speaker wires have resistance, capacitance, inductance that has to be accounted for. You also have to know a lot about the reactances of the drivers in the speaker. I would not know how to do the math without doing a lot of reading beforehand.I do use an RC series filter at my speaker terminals based on the Walker Audio HD Links, which is, according to Al Sekala, a 10R or 100R resistor and a .01uF capacitor. This has virtually no benefit for impedance matching or frequency response flattening at audio frequencies; it's merely a filter for RF. (As I have said probably ad nauseam, it is not a Zobel network.) Try it yourself; it's easy to build one, but you need to use a capacitor that is good at RF frequencies and likewise for the resistor.
Edits: 07/29/16
Lew, A cap in series with a resistor put across the speaker terminals is defined as a Zobel network. Maybe you were thinking of my post about just a cap to roll off highs?? T
"Zobel networks are a type of filter section based on the image-impedance design principle. They are named after Otto Zobel of Bell Labs, who published a much-referenced paper on image filters in 1923.[1] The distinguishing feature of Zobel networks is that the input impedance is fixed in the design independently of the transfer function. This characteristic is achieved at the expense of a much higher component count compared to other types of filter sections. The impedance would normally be specified to be constant and purely resistive. For this reason, they are also known as constant resistance networks. However, any impedance achievable with discrete components is possible.
Zobel networks were formerly widely used in telecommunications to flatten and widen the frequency response of copper land lines, producing a higher-quality line from one originally intended for ordinary telephone use. However, as analogue technology has given way to digital, they are now little used.
When used to cancel out the reactive portion of loudspeaker impedance, the design is sometimes called a Boucherot cell. In this case, only half the network is implemented as fixed components, the other half being the real and imaginary components of the loudspeaker impedance. This network is more akin to the power factor correction circuits used in electrical power distribution, hence the association with Boucherot's name.
A common circuit form of Zobel networks is in the form of a bridged T. This term is often used to mean a Zobel network, sometimes incorrectly when the circuit implementation is, in fact, something other than a bridged T."
Thus a Zobel network is designed based on the impedances of two interfacing elements in the circuit to optimize the match for flattest response. This is not the same as a low pass filter to roll-off hf.
Image result for zobel network The image didn't come through.T
A Zobel network is a series resistor-capacitor (Req-Ceq) network that is connected in parallel with a loudspeaker driver in order to neutralize the effects of the driver's voice coil inductance Le (see note below about Le).
Zobel networks - Wavecor
www.wavecor.com/html/zobel_networks.html
Edits: 07/28/16
An RC network consisting of R = 100 + C = .01uF is a low pass filter when placed in parallel with a speaker input, NOT able to "neutralize the effects of the driver's voice coil inductance" for all voice coils and all amplifiers. My major point was that the R and C values for a true Zobel network need to be calculated based on the amplifier output impedance, the inductance/capacitance of the speaker wire, and the characteristics of the driver voice coil. The HD Link or your putative lo-pass filter would not serve that purpose. It's just a low pass filter. Out.
Not trying to argue. Just trying to get it straight. So, no specific calculation , no Zobel. And the resistor , as I thought, doesn't exclude it from being a low pass filter even if it were a Zobel. Got it. Have an idea how high the cap can be, would a .1 sound better than a .01 with a 10 ohm R and still be ok for the amp to see? Done any experimenting with this. T
my advice is first to try to find the source of the hiss and fix it there, not at the speaker terminal. But now I am a bit confused as to whether you have an inordinate amount of hiss or you're just pursuing perfection (no hiss ever), which eludes most of us. Plus, my thoughts on the lo-pass filter are still the same; you cannot filter out hiss as we know it without losing gobs of musical information in the process. As to this specific question, the value of the capacitor will determine the -3db point of the filter. This is a first order function. So, a 0.1uF capacitor will place the roll-off frequency 10X lower than for a .01uF capacitor. .01uF is safe for musical information; it won't be lost. At 0.1uF, you'd have to listen for yourself. But it really does not matter; we know for sure that hiss is in the audible range, where music lives. You cannot eliminate one without eliminating the other. Which goes back to fixing the hiss at its source.
Edits: 07/28/16
Too late for that. The recording "professionals" seemed to have all to often skipped class that day. T
I cannot recall ever hearing hiss from an LP. One occasionally encounters sibilance, which some might describe as a hissing sound that accompanies ssssss instrumental sounds or words that begin with "s" when sung by a vocalist. Sibilance has its own causes and treatments. On CDs, I cannot recall ever hearing hiss. There's such a thing as tape hiss, and some LPs and CDs were made from tapes, but in those cases I believe that the hiss was suppressed by complex filtering during transfer. So, in summary, I and apparently most others are not bothered by this phenomenon, perfectionists though we all may be. Which is why I suggested that you look to your own gear, not the source material, for the source of the hiss that understandably bothers you.
Lew, It must be that I'm hallucinatin like always or the ringing in my ears. I could use a cure for both! If one does a search for cd hiss one will come up with complaints and explanations. It ain't just little O'l maverick me. The problem is not on all cds. It's very bad on some. T
original recordings done in? Like are these CD's of recordings done back in late 50's early sixties or 70's.
Can you list a few that you are having the hiss issue with?
I have had some like that but it was in the original recordings and there is nothing you can do to remove it except the way I had said before which will degrade the overall sound quality.
Just try to enjoy the music tweaker! Too much thinking is not good! :)
I'll take your advice Cougar. I'm gonna sit back and listen to my Elna Silmic 2's. How's the RC network? Got Ready for Freddie? Back in the day I would bring that around to stores and everyone loved it. T
Edits: 08/07/16
I hate to see you not enjoying your system/updates. There will be other times and things to fine tune in your system. Can't do it all in a few weeks or months.
As for the RC network, It's really made the system sound better, it's more focused now and seems to have more depth. I did change AC plug on my amp the day before and that seemed to open things up too. Both still need to break in more.
I have not ordered that Freddie Hubbard CD yet "ready for Freddie". I will look for it tomorrow.
Have a glass or two of wine or beer and enjoy the tunes! :)
10-4 Get ready!
You really need to get beyond this "sound better" stuff. The zobel network is calculated based on the parameters outlined by Lew. The purpose is to aid in stabilizing the output stage. And a stable output stage does sound better!
If you stick to established electrical engineering theory, the sound quality will take care if it's self.
A bit over my head. It's clear that a Zobel network is not a simply shunt cap to roll off highs as per my last post. If one googles Zobel network the first thing that comes up, when I did it, was a photo of a series resistor and cap across the speaker terminal. Is this not correct? Are you saying that people are using the wrong termination for this simple circuit? Tweaker
I'm just saying that if we don't use these terms properly and consistently, then they lose their meaning, and that cuts down on the ability to communicate. Let's call a high pass filter a high pass filter and leave it at that. A Zobel is something else.
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