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Old 5th May 2014, 11:57 PM   #51891
jcx is offline jcx  United States
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Quote:
Typical amplifiers have a capacitor in the shunt arm of the NFB signal attenuator.
This cap is typically a standard polarised electro.
if you do your V sums correctly I think you will find this series RC has Vin across it - minus the very small +/- input nfb error difference V

I read the Self link as explicitly including this, his book certainly does
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Capacitor distortion in power amplifiers is most likely to occur in the fededback network blocking capacitor...
Audio Power Amplifier Design Handbook 5th ed p204
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Old 6th May 2014, 12:36 AM   #51892
Bonsai is offline Bonsai  Taiwan
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Originally Posted by fas42 View Post
My ideal is to have the system totally transportable - take it anywhere, minimal setup, and it always fires first up with close to optimum quality.
I think that's what Steve Jobs had in mind with the iPod.
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Old 6th May 2014, 03:07 AM   #51893
1audio is offline 1audio  United States
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I'm planning to build a concrete house with a dedicated room for music. Should I avoid metallic rebar? Is there any substitutes?

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1) reduce or eliminate EMI at the source. Always better than at the device.
2) Shielding is not really difficult to understand just difficult to implement with no holes.
3) Steel for low frequencies, conductive for high frequencies (5-10 KHz up).

I can see hum induced from a power cord under my bench. Lift a DUT and the hum changes. However if you have significant current through the rebar, enough to generate an interferor, I would be worried about much more serious issues that hum in the audio. The Rebar may have problems from electrolysis and corrosion if there are currents passing through it. At least you aren't building a $14B bridge with corrosion problems. New Bay Bridge shows signs of rust in critical areas - Bay Bridge - The Sacramento Bee
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Old 6th May 2014, 03:38 AM   #51894
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There are now composite rebar materials that are non metallic. The problem is has your local building code kept up with these developments. Just as Demian has pointed out the steel in a concrete construction has lead to many structural failures due to the corrosion of the steel. The rebar can be coated with a non conductive material but this would raise the cost. I have friends in construction and they will no longer build houses using slab construction, long term the plumbing in the slab can be a real problem.
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Old 6th May 2014, 04:29 AM   #51895
1audio is offline 1audio  United States
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Originally Posted by jneutron View Post
For a single coax, there should be zero external magnetic field. This falls apart if two coax cables connect two chassis.

jn
What happens in the shielded differential case? Especially if there are two differentials in a common shield? The most extreme case in the consumer arena is an HDMI cable with 4 double shielded twisted pair inside an overall shield. (in some cases more. . .) Usually the shields are all tied together at the connectors.
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Old 6th May 2014, 09:28 AM   #51896
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Originally Posted by Bonsai View Post
I think that's what Steve Jobs had in mind with the iPod.
A pocket lighter ?
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Old 6th May 2014, 10:50 AM   #51897
Bonsai is offline Bonsai  Taiwan
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I think he said once he preferred acid. (or, rather, he said if Bill Gates dropped a bit of acid he might chill a bit and get with the groove or something to that effect . . . )
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Old 6th May 2014, 12:44 PM   #51898
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Originally Posted by TNT View Post
I'm planning to build a concrete house with a dedicated room for music. Should I avoid metallic rebar? Is there any substitutes?

//
Thomas Edison used Bamboo . At your location is not the floor insulated from the earth for thermal reasons ? If so the styrofoam or what ever should decouple the slab from the earth. Measure some other's floor to see if the slab is coupled and what field the rebar presents. If all the rebar is tied together then if the wall and ceiling are concrete a fariday cage is a thought.
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Old 6th May 2014, 01:06 PM   #51899
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Originally Posted by 1audio View Post
What happens in the shielded differential case? Especially if there are two differentials in a common shield?
Differential tries to NOT use the shield as a return path. However, if the shield completes a loop, shield currents can induce voltages along the current path.

The best aspect of diff is the return currents are controlled by design, so untoward currents and lack of path control are not a design feature, rather a secondary effect.

jn
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Old 6th May 2014, 02:11 PM   #51900
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