janneman said:
I've been trying very hard to follow this thread, using a fair amount of common sense and "farmers" logic, as well as over 30 yrs of engineering practice in instrumentation systems.......
Were I ever a bewildered soul before, it's gotten alot worse from reading this thread.......
Makes me seriously wonder how man ever managed to get to the moon.............🙄
Or you are deliberately “mixing up” 2 subjects when you know better ?
One is whether one needs a (metallic) shield to keep out RFI, the other is whether one should keep the electronics an signal carrying cables at some distance from metal surfaces to avoid eddy currents.
AuroraB said:
For the sake of this thread, your 30yrs experience is a handicap not an asset. In this view, the audibility of mains fuses was one of the most entertaining topics I've read here lately.
MRupp said:
Or you are deliberately “mixing up” 2 subjects when you know better ?
Martin,
No, I'm not deliberately mixing up anything, I'm just completely at a loss by two knowledgable persons giving opposing advice.
You can't have a metallic enclosure to stop RFI and a non-metallic one to avoid eddy currents at the same time.
BTW is there any documented stuff on that eddy current issue? Instead of anecdotal, I mean?
Jan Didden
Transformer Core
I just got this interesting new core type from Magnetic Metals (magmet.com), DG Zip core (what Magnetics Inc used to call a zig-zag core). They claim they can make any size core without expensive tooling. This would allow bobbin winding with ease of assembly and extremely low gap losses.
I just got this interesting new core type from Magnetic Metals (magmet.com), DG Zip core (what Magnetics Inc used to call a zig-zag core). They claim they can make any size core without expensive tooling. This would allow bobbin winding with ease of assembly and extremely low gap losses.
Attachments
Jan, one could get the best of both worlds by using a loaded resin with low structure factor metal particles. No eddy currents since the particles are separated by insulating plastic, but plenty of mass loading and shielding.
janneman said:
This is a perplexing issue, I agree. I don't think John is any more doctrinaire on it than I am. I first became aware of the benefits of removing metal housings from operating DMC-10's with plastic lids for demo purposes. I also would suggest that it won't work everywhere. And I'm not sure why it works. The eddy current story seems reasonable BUT the cables have shields which should be pretty dominate. It may also be a mechanical issue, and have nothing at all to do with the metal and everything to do with vibration. However the direct microphonics of these guys seems to be very low. Perhaps there are piezoelectric effects in PCB's or something to do with the voltages making the wiring into microphones or ??? Or a million other handwaving arguments with no solid experimental proof. And it all may be a chimera with no real basis.
For what its worth I would still use a metal box for a commercial product. I actually used a double shielded box design on the Nuforce preamp.
Demain and I have somewhat different approaches, but in principle, we essentially agree. We have no trouble discussing this subject privately, so finding differences between us by others is just someone stirring up problems that really do not exist. It is an attempt by Jan to make us look foolish, even to each other. It won't work.
For example, we isolate all our circuit boards from the chassis with Delron or equivalent standoffs. We have a huge piece of Teflon that we mount our input and output connectors on, in order to isolate them from the metal chassis. Internally, we use Teflon covered silver wire WITHOUT shields to isolate ourselves further from the chassis. This is what makes the Blowtorch internal wiring look so strange.
Still, in today's high EMI environment, we feel the need for a metal chassis, AND if we are going to get ANY significant shielding of the magnetic component of the EM wave from an aluminum chassis, it MUST be thick and relatively seamless.
Now counter this, if you dare, Jan!
For example, we isolate all our circuit boards from the chassis with Delron or equivalent standoffs. We have a huge piece of Teflon that we mount our input and output connectors on, in order to isolate them from the metal chassis. Internally, we use Teflon covered silver wire WITHOUT shields to isolate ourselves further from the chassis. This is what makes the Blowtorch internal wiring look so strange.
Still, in today's high EMI environment, we feel the need for a metal chassis, AND if we are going to get ANY significant shielding of the magnetic component of the EM wave from an aluminum chassis, it MUST be thick and relatively seamless.
Now counter this, if you dare, Jan!
Hi Demian,
//"I first became aware of some similarly odd and quite unintuitive 'influences', when improving a Spectral pre-amp, over 20 yrs. ago. This was rather ahead of its time in some ways, having entire ground-planes on both sides of the full-size PCB which were also gold-plated throughout, and this appearance together with a very neat and careful component layout, caused to me as an engineer to appreciate the aesthetics of the populated PCB when the case was open. Having seen at some audio show, a similar unit with a clear acrylic top which was intended to show-off this rather better than average internal appearance, I wished to emulate this 'exposed internals' effect, so I duly made up an 8mm Perspex (Lexan) top for my own pre-amp.
However, and especially as this pre had massive gain to suit even very low-output MC cartridges without any added step-up device, I was quite concerned about the possibility of RFI, or whatever, affecting the overall sound, and probably detrimentally. Accordingly, before finally screwing down this new cover more permanently, I considered it wise to conduct some listening trials to determine this potential, one way or the other.
Somewhat to my surprise (and quite the opposite to all expectations) not only did the new cover not make the sound worse, it actually sounded marginally better than with no lid at all. Being very puzzled by then, but interested in getting to the bottom of this anomaly, I experimented further for several more days, and there was no doubt at all that the preferred order of 'sonic goodness' was: 1st. the new cover, 2nd. no cover, and last (by a more noticeable margin), the original metal top. The entire enclosure was very shallow on these Spectral pre-amps, so the proximity of the covering material was quite close to the circuit board, and almost touching the tops of the taller components.
The conclusion I reached after a couple of weeks playing around with these alternatives, was that placing substantial areas of metal near to sensitive electronic circuits was detrimental to the overall sound, and that damping effects from the dense and quite heavy acrylic top, actually benefitted the overall sound, as a bonus."//
This is a quote from my post of 03-31-2006, not having any idea that anyone else had discovered this phenomenon, of course.
Probably just another one of those coincidences, though! 😉
Regards,
//"I first became aware of some similarly odd and quite unintuitive 'influences', when improving a Spectral pre-amp, over 20 yrs. ago. This was rather ahead of its time in some ways, having entire ground-planes on both sides of the full-size PCB which were also gold-plated throughout, and this appearance together with a very neat and careful component layout, caused to me as an engineer to appreciate the aesthetics of the populated PCB when the case was open. Having seen at some audio show, a similar unit with a clear acrylic top which was intended to show-off this rather better than average internal appearance, I wished to emulate this 'exposed internals' effect, so I duly made up an 8mm Perspex (Lexan) top for my own pre-amp.
However, and especially as this pre had massive gain to suit even very low-output MC cartridges without any added step-up device, I was quite concerned about the possibility of RFI, or whatever, affecting the overall sound, and probably detrimentally. Accordingly, before finally screwing down this new cover more permanently, I considered it wise to conduct some listening trials to determine this potential, one way or the other.
Somewhat to my surprise (and quite the opposite to all expectations) not only did the new cover not make the sound worse, it actually sounded marginally better than with no lid at all. Being very puzzled by then, but interested in getting to the bottom of this anomaly, I experimented further for several more days, and there was no doubt at all that the preferred order of 'sonic goodness' was: 1st. the new cover, 2nd. no cover, and last (by a more noticeable margin), the original metal top. The entire enclosure was very shallow on these Spectral pre-amps, so the proximity of the covering material was quite close to the circuit board, and almost touching the tops of the taller components.
The conclusion I reached after a couple of weeks playing around with these alternatives, was that placing substantial areas of metal near to sensitive electronic circuits was detrimental to the overall sound, and that damping effects from the dense and quite heavy acrylic top, actually benefitted the overall sound, as a bonus."//
This is a quote from my post of 03-31-2006, not having any idea that anyone else had discovered this phenomenon, of course.
Probably just another one of those coincidences, though! 😉
Regards,
I was doing all of this in the early 90's and sort of lost interest as digital redefined audio. And my income was elsewhere so it all receded fo a while. But now that my income is from digital at very high data rates the analog stuff is interesting again.
At first the magnetic issues seemed to be the cause, but the Spectral covers are aluminum at .062" thick. The Plex sounded much better (a lot of dealers picked up on this) but did not offer any protection from EMI. I think the biggest reason the Spectral was very sensitive to emi/rfi was the high input impedance on the phono section. I tried to keep the impedance high and the capacitance low so it would not interact with the source. I have strong opinions about loading cartridges as well but that's another topic.
At first the magnetic issues seemed to be the cause, but the Spectral covers are aluminum at .062" thick. The Plex sounded much better (a lot of dealers picked up on this) but did not offer any protection from EMI. I think the biggest reason the Spectral was very sensitive to emi/rfi was the high input impedance on the phono section. I tried to keep the impedance high and the capacitance low so it would not interact with the source. I have strong opinions about loading cartridges as well but that's another topic.
When you put these 'coincidences' together, you get real knowledge. That is what separates mid fi from hi fi.
demian:
could you be encouraged to share your views on cartridge loading (or other phono related stuff) the analogue topics section of the forum?
i, for one would be interested in hearing them.
mlloyd1
could you be encouraged to share your views on cartridge loading (or other phono related stuff) the analogue topics section of the forum?
i, for one would be interested in hearing them.
mlloyd1
1audio said:
1audio said:
I use a Kistler charge amplifier connected to a metal disc and a ceramic handle. I've calibrated it against a static charge meter for my needs, but a simple relative measurement device can be made with simple gain stage and a FET input. Take a look at the Kistler site for charge amplifier circuit ideas.
Plastics and the charges they hold is an interesting study. Unless a plastic has a dissipative filler added they will hold quite a charge. Essentially the charge has no conductive path through an insulator to discharge.
My curiosity stems from the documented concerns as to the sonically detrimental effects of any ferrous material within blocks of an audio circuit, along with the noted preferences for different dielectrics in capacitors and wiring… What effect do the electrostatic properties play? Is a wire vibrating in an electrostatic field affected in a similar manner? Could sonic changes related to burn-in be related to electrostatics?
So many questions, so little time.
Mike.
Attachments
MikeBettinger said:
Sounds like a condenser microphone to me. .
I'll check out the Kistler site. I have a charge amp here somewhere.
P.S. I have a patent on applying a bias to an audio cable, and I still am not really sure why it helps but it seems to.
mlloyd1 said:
Let me put together some factual foundation before I explain my position. That will take a little while. Hopefully next week.
Or its precise opposite, the claimed sonic superiority of designs using lots of transformers, and a lot of big ones, too, in the box and in the signal path. Or anything with tubes, for that matter. Lots of ferrous stuff right there in the active devices.
There are no perfect conductors and there are no perfect insulators so any dielectric charge will eventually drain off. I'm unsure about a perfect vacuum (any physics majors out there?)
Here is an excerpt from George Cardas and a link. He thinks that draining off a charge is a significant part of "break in". There's a lot more on this if you follow the link. I don't know if George is right, but it is as good a story as I've read in other places.
George Cardas:
There are many factors that make cable break-in necessary and many reasons why the results vary. If you measure a new cable with a voltmeter you will see a standing voltage because good dielectrics make poor conductors. They hold a charge much like a rubbed cat’s fur on a dry day. It takes a while for this charge to equalize in the cable. Better cables often take longer to break-in. The best "air dielectric" techniques, such as Teflon tube construction, have large non-conductive surfaces to hold charge, much like the cat on a dry day.
http://www.cardas.com/content.php?area=insights&content_id=12&pagestring=Cable+Break-In
Here is an excerpt from George Cardas and a link. He thinks that draining off a charge is a significant part of "break in". There's a lot more on this if you follow the link. I don't know if George is right, but it is as good a story as I've read in other places.
George Cardas:
There are many factors that make cable break-in necessary and many reasons why the results vary. If you measure a new cable with a voltmeter you will see a standing voltage because good dielectrics make poor conductors. They hold a charge much like a rubbed cat’s fur on a dry day. It takes a while for this charge to equalize in the cable. Better cables often take longer to break-in. The best "air dielectric" techniques, such as Teflon tube construction, have large non-conductive surfaces to hold charge, much like the cat on a dry day.
http://www.cardas.com/content.php?area=insights&content_id=12&pagestring=Cable+Break-In
1audio said:
This is kind of an off beat application for charge amplifiers but... To get a feel for their sensitivity, hook the input up to a plate of some sort (hang it in the air not touching anything), put your hand near it then rub your foot on the carpet; a 1kv + charge on your hand (don't touch the plate, only the field from your hand). Very sensitive! All kinds of food for thought.
It's possible the bias on the cable dominates and controls the charge on the cable's dielectric, makes it predictable and constant (?). Check out the cables used with the Kistler's on their site. The one used with my detector is from them.
Regards, Mike.
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