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Old 3rd July 2009, 11:04 AM   #161
KSTR is offline KSTR  Germany
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Quote:
Originally posted by 1audio
Be sure to use good feedthrough caps to get in and out of the box.
Hhm, when the goal is to introduce common-mode impedance, then (larger) feedthrough caps on the output (to the device to be powered) are not a good idea, IMHO. This is sort of a dilemma, since a standard shielded cable from filter to device has the same problem. Maybe it would be best to have seperated shielded boxes for filter, psu and decive all together in one bigger shielded box?

- Klaus

BTW, how does solid brass compare to solid AL in terms of shielding effectiveness
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Old 3rd July 2009, 11:13 AM   #162
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Feedthroughs work. Do not forget that you somewhere connect signal ground (0V) to the box anyway, and you have a lot of caps from +Vs and -Vs to ground anyway. Several nF of the feedthrough would not worsen the situation.

It makes no sense to design a nice box and then use long untended wires inside.
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Old 3rd July 2009, 11:25 AM   #163
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in a case of separate psu box( like blowtorch) , row psu with CRC filter ,is better put the last cap in the audio signal box(with shunt)?
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Old 3rd July 2009, 11:31 AM   #164
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Quote:
Originally posted by nicoch46


Right , this is a problem as I'm not EE ,I'm here on diyaudio, condemned to buy a kit or build good stuff like Salas shunt.....

Do you maintain the opinion then, that a psu for audio is a special kind of psu?

Jan Didden
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Old 3rd July 2009, 11:46 AM   #165
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yes ,I find no other explanation: whay if I swap on borbely design caps or diode the sound change a lot ?

ok cooking parts is not like a design....shunt can be audio psu


the blowtorch psu with: 3 passive stages, then 3 active stages of regulation and noise reduction, on each channel and each supply voltage, look like hiend psu....
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Old 3rd July 2009, 02:39 PM   #166
Magura is offline Magura  Denmark
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Quote:
Originally posted by PMA


You have to shield them.

Quote:
Originally posted by 1audio


Lots harder to do than it may seem to be. And the shielded chokes are limited in size and value. A Mu Metal shield around a power inductor may work, or it may saturate real fast if the current is high.

It's actually not all that to shield an inductor. With some help from Dimitri, I made a 5mH shielded inductor for a power amp PSU, some time ago.

It's a mix of ferritic stainless steel and copper shield.

Magura
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Old 3rd July 2009, 03:54 PM   #167
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If you have long unprotected internal leads, then I recommend a cigar box lined with aluminum foil, as an adequate shield. OK, PMA?
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Old 3rd July 2009, 05:53 PM   #168
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Quote:
Originally posted by PMA
LC, if necessary.
Duh, isn't that the same as a feedthrough filter ?
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Old 3rd July 2009, 06:13 PM   #169
1audio is offline 1audio  United States
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Quote:
Originally posted by Magura






It's actually not all that to shield an inductor. With some help from Dimitri, I made a 5mH shielded inductor for a power amp PSU, some time ago.

It's a mix of ferritic stainless steel and copper shield.

Magura
Did you characterize the effect on the inductor of shielding it? You would see the inductance change and it would have a saturation point as well. When saturated the shield effectively vanishes so you need to be sure you stay below that limit. Also it will affect the HF performance but the coil pictured will not have the best HF performance anyway.
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Old 3rd July 2009, 06:16 PM   #170
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Demian, what do you mean by hf performance? Parasitic capacitance?

Jan Didden
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