From what JN describes, it would be pretty easy to make and wouldn't need a larger gap if carefully done... A single printed turn has almost zero added thickness.
Are there any measured results for a metal detector type system?
One last mention.
While the shorting ring is leveling "measured" inductance, it does so by eddy current based field exclusion. Unfortunately, this is the exact technique used to make magnetic brakes. The result is asymmetrical viscous damping, as well as assymetrical eddy dissipation. When a lf signal is creating large excursion, a riding hf signal will alternate between two environments, each with different losses and damping.
None of the HP or Agilent meters I use are capable of discerning the assymetry during vc movement. The best I could hope for is locked rotor measurement of Rs vs frequency.
Jn
While the shorting ring is leveling "measured" inductance, it does so by eddy current based field exclusion. Unfortunately, this is the exact technique used to make magnetic brakes. The result is asymmetrical viscous damping, as well as assymetrical eddy dissipation. When a lf signal is creating large excursion, a riding hf signal will alternate between two environments, each with different losses and damping.
None of the HP or Agilent meters I use are capable of discerning the assymetry during vc movement. The best I could hope for is locked rotor measurement of Rs vs frequency.
Jn
Was the LM4702 ever used in any premium domestic products? I know this and the TI equivalent had an ardent DIY following but assumed it's normal home was in 5.1 and 7.1 receievers more because hard to spin a good marketing story off using a chip to do most of the work vs hand selecting devices under a blood moon.
George
To elaborate, locked rotor measurement of Rs vs frequency vs location.
Also, given how easy it is to incorporate flat loops into the body of a vc former made with fiberglass/carbon composite, why not also include a few temperature monitoring strips. Find a material that has a reasonable temperature resistance coefficient and embed it. By making it in a stripline configuration, it will not intercept any time varying flux so could be run at say 100 mA or so with drop monitored for voltage.
With a steady BL product, this puppy would allow for constant current drive with the ability to directly measure the voice coil temperature.
jn
I spent a week in China originally at the request of the ESS apps guy (they still did not have a headphone driver) visiting all the majors putting together chip sets. It was hard to believe there was one ESS apps guy working almost 24/7 to cover all the business.
Doing actual DBT was culturally unacceptable so it was difficult for me to say any of the reference designs actually sounded any different. At one place they wanted extra headroom on the driver and I finally realized they wanted to damp the output with a resistor 🙂 sound familiar?
It was our editorial policy to not put any audiophile hubris in our datasheets or app notes. IIRC Burr Brown might have been the first.
How very odd. My post 4133 is a combination of two individual posts now. I do not recall quoting and responding to two posts within one reply.
Was it combined for a reason?
jn
Was it combined for a reason?
jn
No, the forum sw seems to combine posts automatically if the time between posts is short, happened to me several times, too.
And thank you for your input on the magnetic stuff, I'll need some time to digest that....
And thank you for your input on the magnetic stuff, I'll need some time to digest that....
I would like to acknowledge that National Semiconductor was very helpful, in recent years in making competitive and actually very good sounding IC's for audio. My kudos to Mark Brasfield for making a listening room with good loudspeakers, etc. That is the only way to resolve the subtle differences, both short and long term in IC's, caps, etc. This double-blind business will forgive just about anything, and that is why we don't use it much. We need better resolution, usually electrostatic headphones direct driven by tubes, to really resolve really subtle differences. Now that is not what we normally like to listen to, (electrostatic headphones) because we have to wade through the compromises made while recording the material as well, and more forgiving headphones actually make listening more enjoyable, but to resolve differences, we have to 'put it on the racetrack' to test it properly.
I use a National Semi IC in the input of the JC-3 series phono stages. It passed my listening tests when directly compared to the AD797 which was the primary competition. There was still a difference sonically, but both IC's sounded pretty good (but different) and the National Semi device was less than 1/2 the price. For instrumentation, I would still chose the AD797, because it would MEASURE slightly better, and for test equipment, this is most important.
I am impressed that National made a serious effort to make IC based power amps. I know how much trouble it is to make an all discrete one, and most here cannot afford the time to make, or the money for a power amp like I design. High negative feedback hides many things. '-)
I use a National Semi IC in the input of the JC-3 series phono stages. It passed my listening tests when directly compared to the AD797 which was the primary competition. There was still a difference sonically, but both IC's sounded pretty good (but different) and the National Semi device was less than 1/2 the price. For instrumentation, I would still chose the AD797, because it would MEASURE slightly better, and for test equipment, this is most important.
I am impressed that National made a serious effort to make IC based power amps. I know how much trouble it is to make an all discrete one, and most here cannot afford the time to make, or the money for a power amp like I design. High negative feedback hides many things. '-)
I'll be impressed when one of them makes no global feedback PA's with the THD does not matter song and dance.
Believe me, we aren't that bored and really have better things to do. There are days when all I do is moderation duties, same with the other guys.
I also have had posts combined automagically.
-Chris
I totally forgot to respond to this😀😀
Built a pin router, big learning curve!!!
Made an indexing jig for gears as well as small parts jigs. Learned early on, there is no such thing as too much clamping, or fixture mass. I've gotten it so the routed surfaces are polished and require no sanding. Also, gears with teeth within a mil after cut. (Right after cut...wait five minutes, it's changed. It is wood after all). And mil being thousandth of an inch.
For a while, I was losing one or two bits a day. At 21 bucks (usd) per, 'twas interesting. (1/8th dia, half inch long carbide).Wasn't sure I'd ever see a dull bit. Now, I seem to know what I'm doing. (Yah, wishful thinking).
Also am learning about veneering. Most interesting thing was that the glue goes on the base, and when you put the veneer on, very very quickly clamp the day lights out of it. The idea is that you need to fix it in place before the veneer has a chance to expand as it absorbs the glue (or epoxy). Otherwise it builds stress across the grain and will eventually crack.
I first learned this when I glued two pieces of 8 inch by 8 inch, 1/8th maple, grains at 90 degrees. It "Pringled". So I either go odd number of layers or coat the outer surfaces with epoxy as well and clamp it using wax paper as a release paper. Clamping is with an 8 ton shop press.
Gotta have a hobby for retirement...so far, about 1700 dollars in wood, but man am I having fun!!!
I would apologize for the off topic, but this is the blowtorch thread, no?
Jn
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I was under the impression that the shorting ring resistance was negligible compared to it's mutual inductance with the voicecoil, and that it's leakage inductance would probably dominate over effects from it's resistance.
For instance with a trace over a ground plane, the ground plane effectiveness is limited by the plane's own leakage inductance (the portion of it's inductance that isn't coupled to the trace).
For instance with a trace over a ground plane, the ground plane effectiveness is limited by the plane's own leakage inductance (the portion of it's inductance that isn't coupled to the trace).
Shorting rings work because they create a magfield that is opposite to the field that creates the eddy currents the shorting ring magfield tries to cancel the field. Since the ring is not superconducting, it is not 100% effective.
Any eddy losses in the ring will be in phase with the vc current, so would be reported as resistive loss.
The drop in inductance is a direct result of the eddy currents (with those losses). The actual value of the effective resistance as seen by the voice coil, that would have to be measureed.
The ground plane example you cite... The current has to decide how it's going to flow based on how easy the path is. The common theme is, the current centroids are trying to get together, resistivity and inductance are players in that game..
Jn
Ps.. My main concern with shorting ring is that people assume that a flat inductance measure means the vc environment is identical along the entire mechanical path. That is why I pointed out the difference in how the inductance drops. There are significant differences.
Any eddy losses in the ring will be in phase with the vc current, so would be reported as resistive loss.
The drop in inductance is a direct result of the eddy currents (with those losses). The actual value of the effective resistance as seen by the voice coil, that would have to be measureed.
The ground plane example you cite... The current has to decide how it's going to flow based on how easy the path is. The common theme is, the current centroids are trying to get together, resistivity and inductance are players in that game..
Jn
Ps.. My main concern with shorting ring is that people assume that a flat inductance measure means the vc environment is identical along the entire mechanical path. That is why I pointed out the difference in how the inductance drops. There are significant differences.
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What is interesting is that the shorting ring/eddy current/inverse magfield thing is exactly the same as what goes on with a shielded cable and ground loop. When an IC forms a ground loop between two chassis both tied to ac ground with 3 prong plugs, the loop trapped magfield creates shield currents 90 degrees out of the magfield, it's resultant currents are 90 degrees more out, causing the 180 degree magfield cancellation. Shield resistance of course limits the effectively..(This is detailed in IEEE-STD-1050, retired)
Jn
Ps...just wàiting to see these two posts combine by the site...automagically. ( oh man, I just loved that word, I am really gonna use it at work.....without attribution of course, I need to look smart)lost cause of course..
Jn
Ps...just wàiting to see these two posts combine by the site...automagically. ( oh man, I just loved that word, I am really gonna use it at work.....without attribution of course, I need to look smart)lost cause of course..
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This thread reminds me of Jona Lewie's "You'll always find me in the kitchen at parties".
Or maybe this thread is the party! I'm not sure.
The quality of speaker design discussion here seems very high. I can't help thinking these posts deserve to be in the speaker section or a not yet created design section so they don't get completely lost.
Normally a mod would do some sorting on the pretext of it being off topic but as far as I can tell almost everything in this thread is off topic. 😀
Or maybe this thread is the party! I'm not sure.
The quality of speaker design discussion here seems very high. I can't help thinking these posts deserve to be in the speaker section or a not yet created design section so they don't get completely lost.
Normally a mod would do some sorting on the pretext of it being off topic but as far as I can tell almost everything in this thread is off topic. 😀
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