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Old 8th July 2005, 06:59 AM   #21
solar2 is offline solar2  United Kingdom
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I e-mailed autocostruire via the website link and got a very quick reply. English is fair!
Just another thought, one could always try experimenting with a mu-metal screen between the inductors and the rest of the circuit. I guess one of the mechanisms for the EMI to be picked up are the component leads acting as aerials, so in this respect SM components have an advantage despite being a pig to solder.
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Old 8th July 2005, 09:10 AM   #22
dillo is offline dillo  Italy
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yes, a mu-metal screen (better if grounded) would suppress EMI, but would act again as a core material causing hysteresis and large eddy currents (a screen is a conductive solid piece); thus spoiling up the effort for air cored chokes.
Tripath on their evaluation boards provides grounded connection for a screen, but that case is simpler because inductors are cored, so concentrate most of the magnetic field inside the core.
But, since starn02 proved that there isn't much nasty EMI, i think it is better to try and add a screen or change for other chokes solutions only if someone finds interference.
Kanaddict, I don't think that the small angles between inductors is there to diminish mutual inductance: the chokes are too close and most of all they should be perpendicular to each other for this purpose. To me is only a problem of spacing.
Bye bye
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Old 8th July 2005, 10:17 AM   #23
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Quote:
Originally posted by dillo
But, since starn02 proved that there isn't much nasty EMI, i think it is better to try and add a screen or change for other chokes solutions only if someone finds interference.
Kanaddict, I don't think that the small angles between inductors is there to diminish mutual inductance: the chokes are too close and most of all they should be perpendicular to each other for this purpose. To me is only a problem of spacing.
Bye bye
Thanks Angelo !

When I'll get my kit (probably september), I'll build it as indicated & see if there is any problem. Be sure that I'll post a little review.

Best regards,
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Old 9th July 2005, 10:09 PM   #24
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Quote:
Originally posted by dillo
yes, a mu-metal screen (better if grounded) would suppress EMI, but would act again as a core material causing hysteresis and large eddy currents (a screen is a conductive solid piece); thus spoiling up the effort for air cored chokes.
Tripath on their evaluation boards provides grounded connection for a screen, but that case is simpler because inductors are cored, so concentrate most of the magnetic field inside the core.
But, since starn02 proved that there isn't much nasty EMI, i think it is better to try and add a screen or change for other chokes solutions only if someone finds interference.
Kanaddict, I don't think that the small angles between inductors is there to diminish mutual inductance: the chokes are too close and most of all they should be perpendicular to each other for this purpose. To me is only a problem of spacing.
Bye bye
A Faraday Cage maybe?
http://en.wikipedia.org/wiki/Faraday_cage
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Let your ears by your judge
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Old 11th July 2005, 12:09 PM   #25
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Hallo T-Amp Tweakers,

today i found good Information about Air Cokes on

www.colmar.com/Shavano/inductor-info.html

Greetings from Germany
Jürgen
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Old 11th July 2005, 12:35 PM   #26
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Sorry,
its www.colomar.com/Shavano

Jürgen
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Old 11th July 2005, 04:48 PM   #27
mourip is offline mourip  United States
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Quote:
Originally posted by solar2
I e-mailed autocostruire via the website link and got a very quick reply. English is fair!
Just another thought, one could always try experimenting with a mu-metal screen between the inductors and the rest of the circuit. I guess one of the mechanisms for the EMI to be picked up are the component leads acting as aerials, so in this respect SM components have an advantage despite being a pig to solder.
Hi Solar2,

Thanks for the reply. I tried again but have not gotten a reply. I wonder if you or anyone else has a direct email address for them. Perhaps you could get it from their reply...

Best,

Paul
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Old 11th July 2005, 04:59 PM   #28
dillo is offline dillo  Italy
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Quote:
Originally posted by CambshireGordon


A Faraday Cage maybe?
http://en.wikipedia.org/wiki/Faraday_cage

Mmmmh, well, a Faraday cage of non magnetic material would have no hysteresis, but would cause losses due to eddy currents...
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Old 14th July 2005, 08:41 PM   #29
starn02 is offline starn02  Italy
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I insist guys ... no EMI or RF noises from my Kit from www.Autocostruire.com. Even if I keep it on the desk between computers and neon lamps ..... so what's the problem?
Keep in mind also that EMI waves decay exponentially, so it's really unlike that you'll induce disturbances on other equipment.
Yesterday, solicited by all these discussions, I tried wondering with an oscilloscope probe around the kit. Well, you can catch some high frequency "carrier" when the tip is near the air core inductors, but it rapidly decays to zero if you move out of the core. I was unable to trigger the frequency properly (I have a 20 MHz scope), so probably it's a "spread spectrum" carrier that's outside the audio band. This is in accordance with what you find in the Tripath docs.

I also downloaded an interesting application note where the nature of "clipping" is described ... see http://www.tripath.com/downloads/an6.pdf.

So, if any "carrier" residual is still present, it should make no harm at the sound quality. Take a look at the application note ... have you ever seen an amp that stands the clipping in such a correct way ?
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Old 15th July 2005, 10:07 AM   #30
solar2 is offline solar2  United Kingdom
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My fears have definitely been allayed. I have just tried the Autocostruire air-cored inductors on my T-Amp and they sound great! It has really cleaned the treble up. Up to now, there were only 2 areas in which my existing amp beat the T-Amp (modded with 4.7uF caps, no I/P inductors, 12V car battery powered, decent case/connectors, no volume pot) and that was the treble which was a bit rough/grainy/overpowering and the bass which is lacking in “clout”. The treble is now silky smooth, so clearly the radiation “problem” does not seem to be a problem. No screens or shields necessary.

Hopefully putting some big caps across the battery will lower the ESR and improve the bass. I certainly hope so as the little amp is now so good, that even with the bass problem, it’s hard to go back to my trusty old amp. (Onix OA21 which is a very highly regarded transistor amp reckoned to sound as good as £1000 Naim amps)
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