Hi Jbaudiophile, thanks! I caught that earlier. The interesting part I took from that is low frequency magnetic shielding was less a design consideration than RF, and RF was important enough to drop $3k on casework. (Way off topic aside: Almost 15 years ago I tested a passive wired out in a near-identical fasion on an Audio Precision and found crosstalk sensitive to placement. The best wiring loom, though far from best looking, was surprisingly similar. It's been so long but I recall the only improvement came from riveting a small aluminum shield to the case between the left and right channel wiring from the selector to output pots. Better than 110 dB across the board.)
I can't see how anyone needs to drop $3k on a case for RF.
Use a few ferrite beads and copper shielding is plenty enough.
Tom
EE
Use a few ferrite beads and copper shielding is plenty enough.
Tom
EE
Hi John,
I actually tried that stuff (to fix a problem). Didn't work that well and the spray is expensive. I hear it helps with CD players. 😉
-Chris
I actually tried that stuff (to fix a problem). Didn't work that well and the spray is expensive. I hear it helps with CD players. 😉
-Chris
Yup,
Sprayed it three times. Had my doubts and I was right!
Why do manufacturers use plastic cases for sensitive electronics ?? 😕
-Chris
Sprayed it three times. Had my doubts and I was right!
Why do manufacturers use plastic cases for sensitive electronics ?? 😕
-Chris
I tried building a case from plexiglass with a layer of gold/palladium vapour deposited on the interior surfaces, making sure there was electrical interconnection between each piece when it was assembled.🙄 It failed miserably at shielding RFI.
Guess I should have deposited a layer thicker than a few angstroms.
It did look really cool though.😉
Guess I should have deposited a layer thicker than a few angstroms. It did look really cool though.😉Hi, RDF, Hi, John, Hi, all others,
3K$ too much for a case ?
Ah ? So, John, please explain us why your own Blowtorch case is in this cost area?
As an evidence, amateurs have rarely access to CMC machining tools, and use whatever they can pick... RDF sais that it was years ago, and radiated RFI hadn't come yet at such a pollution we now have...
So, IMO, a serious electrical AND magnetic shielding is mandatory for sensitive stages. But the case has to be fairly well shielded too..
All internal cabling is seen as small antennas with air RFI... The industrial grade mains filters are most of the time ineffective to prevent the mains RFI, but when they have 2 coils or more...
I am currently studying and gathering papers arount the mains noise / RFI noise,.. in order to be able to have an "identity card" (frequency range, levels,..) for what we are facing... Not so easy to achieve ! But for what I gathered yet, seems that we have 3 big pollution groups to fight against with the appropriate means : air radiated RFI, mains radiated RFI, and mains industrial/citizen noises (impulses,...).
Anyone that has data or mesurements on these can drop me a line directly... Will sum up and report next on the forum...
Jbaudiophile
3K$ too much for a case ?
Ah ? So, John, please explain us why your own Blowtorch case is in this cost area?
As an evidence, amateurs have rarely access to CMC machining tools, and use whatever they can pick... RDF sais that it was years ago, and radiated RFI hadn't come yet at such a pollution we now have...
So, IMO, a serious electrical AND magnetic shielding is mandatory for sensitive stages. But the case has to be fairly well shielded too..
All internal cabling is seen as small antennas with air RFI... The industrial grade mains filters are most of the time ineffective to prevent the mains RFI, but when they have 2 coils or more...
I am currently studying and gathering papers arount the mains noise / RFI noise,.. in order to be able to have an "identity card" (frequency range, levels,..) for what we are facing... Not so easy to achieve ! But for what I gathered yet, seems that we have 3 big pollution groups to fight against with the appropriate means : air radiated RFI, mains radiated RFI, and mains industrial/citizen noises (impulses,...).
Anyone that has data or mesurements on these can drop me a line directly... Will sum up and report next on the forum...
Jbaudiophile
Vapour deposition is a well known way the make plastic parts Shielding. At my formar job I made mechanical designs for VHF and MF radio comunication equipment. Ofthen there was a narrow but fine line between shielding and ajusting. Most ofthen the joints was problem areas where we used pressed copper fingers to enshure close an suficient contact between elements. But to me the process of shiedling (ajusting) was a bit of black chicken woodo like, as it seemed almost impossible to predict the capacitive and inductive coupeling between the differnet casing elements. (both reciver and transmitter in one boks). The startpoint seemed to be a solid gnd placed on a cast aluminium chassis with the pcb's clamped in between layers of conductive gaskets. This was not too different from the BTorch. Except that the Torch has no TX. And the reciver is rather poor but never the less proned to pick up noise. I am shure that a few stratecally placed caps will take away any possibility of the torch becoming a RF reciver. a few pF in the input and ditto in the feed back will effectively kill any possibility of radio reception. Also similar decopling of the power supply (arround resistors) can do away with RF artefacts.
RF paper
An importir here import a "RF Paper" from USA. It looks like thick paper (like wall paper), the upper and lower are paper but sandwiched in the middle is fibres (black, like carbon fibre), it can be seen if we put light towards it.
This paper is said to prevent RF. It is placed on preamp / amp casing, covering the whole case.
Anyone has experience with this RF paper?
An importir here import a "RF Paper" from USA. It looks like thick paper (like wall paper), the upper and lower are paper but sandwiched in the middle is fibres (black, like carbon fibre), it can be seen if we put light towards it.
This paper is said to prevent RF. It is placed on preamp / amp casing, covering the whole case.
Anyone has experience with this RF paper?
Do you mean Stillpoints ERS Cloth?
Theres also a Japanese product that makes similar claims called Triguard Ultra , seems to be mainly used to wrap power cords.
I have no experience with either product though.
regards
James
Shielding means making a faraday cage arround the circuit and the cablage. but that is only half the story as all cables going in and out works as antenneas. Careful decoubling with small ceramic caps arround interfaces may solve the issue (if there is an issue). Making the cage tight means many screws as any crack may not be any longer than the wave lengt you're shielding for alternatively one can use copper fingers or other types of conductive gaskets.
Best
Micahel Børresen
Best
Micahel Børresen
In the website there's no picture of it. But from the explenation (carbon fibres), it seems this is the one.
The surface of the paper is different front and back. One has pores.
I tried this but seems to make no difference. Is that to handle RF we should use thick aluminum like Blowtorch (using RF paper or any thin "magical" stuff is nonsense?)
The RF paper is very interesting and hi-tech, but aluminum foil is actually a pretty good shield at frequencies near audio, and better than RF paper. Thanks SY, for turning me on to this. However, at microwave frequencies, the RF paper may well be superior, and it works differently, which could have advantages.
We use the thick aluminum case for several reasons. First, it is a pretty good RF shield. Second, aluminum is non-magnetic. Third, it is structurally strong and well damped. It is NOT flimsy.
The biggest problem is that it is very expensive.
We use the thick aluminum case for several reasons. First, it is a pretty good RF shield. Second, aluminum is non-magnetic. Third, it is structurally strong and well damped. It is NOT flimsy.
The biggest problem is that it is very expensive.
Yes, it's ugly, but ham radio people have long made cases out of unetched PCB material. Cut it to any size or shape desired and solder it together. Soldering the inside of the seams yields a somewhat more attractive box, but is a pain in the rump.
The copper foil is non-magnetic so that's not a worry. The PCB substrate isn't going to win any awards for physical strength, either. However, if you think you have an RF problem and want a way to test before plunking down big bucks for a milled aluminum case, this gives you a relatively inexpensive way to prototype an RF resistant box for your circuit.
Grey
The copper foil is non-magnetic so that's not a worry. The PCB substrate isn't going to win any awards for physical strength, either. However, if you think you have an RF problem and want a way to test before plunking down big bucks for a milled aluminum case, this gives you a relatively inexpensive way to prototype an RF resistant box for your circuit.
Grey
Aluminium : how about copper ?
Regards.
Philippe (who just saw Grey posted something about pcb, but would like to know if there is sometinhg special about aluminium vs copper)
Regards.
Philippe (who just saw Grey posted something about pcb, but would like to know if there is sometinhg special about aluminium vs copper)
I have a roll of copper foil that I purchased from www.onlinemetals.com
I used a small section to shield the electronics package of a bass guitar. I plan on using it when I build the casework for my new MC Phonostage. It's pretty affordable stuff and looks really cool.
Nate
I used a small section to shield the electronics package of a bass guitar. I plan on using it when I build the casework for my new MC Phonostage. It's pretty affordable stuff and looks really cool.
Nate
Yes, but you can use aluminum foil to wrap baked potatoes. And it has years of use lining hats to repel the CIA mind-control lasers. If it's good enough for that, it's good enough for audio shielding.
Inputs on wrong side?
The reason that Naim (and others) put the inputs on the right hand side is legacy. Typical turntables have the tonearm cable/wiring exiting on the right side. Therefore, placing the high gain RIAA stage on the right side, 'under' the tonearm, and placing the mains input cables/power supply on the left side, minimises the interference.
A number of integrated amplifiers use the same layout
These days, with line level sources dominating, it is just a style issue.
The reason that Naim (and others) put the inputs on the right hand side is legacy. Typical turntables have the tonearm cable/wiring exiting on the right side. Therefore, placing the high gain RIAA stage on the right side, 'under' the tonearm, and placing the mains input cables/power supply on the left side, minimises the interference.
A number of integrated amplifiers use the same layout
These days, with line level sources dominating, it is just a style issue.
What I said about Brits and doing things 'wrong' was just a joke. I though it was evident. The original question was if there were any technical benefits to placing the BT volume control on the left (nothing to do with the input RCAs position). It's all there a couple of pages back.
Regards,
Milan
Regards,
Milan
- Status
- Not open for further replies.