John Curl's Blowtorch preamplifier part II - Page 3375 - diyAudio
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Old 27th January 2013, 10:52 PM   #33741
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Quote:
Originally Posted by pooge View Post
Do it with the realization that it is not directed to an "audiophile fantasy", but includes real world experience and measurements by the likes of Whitlock, Muncy and Brown.
I don't know those guys, i make my own measurements with the real cables on long distances.
When it is about symmetrical cabling, the first important thing is EMI/RFI protection. Then, ground loops (racks) and AC leakages. Never forget that you have >60db common mode rejection, reason why symmetrical is 1000X better.
We compared this one with 5 others and it was our choice. Now, make measurments on *this* cable, to prove *this* cable have poor symmetry:. You will be very surprised :-)
All this controversy is like talking about -140dB distortion.
Now, the reason why this cable does not suffer from the 'current centroid asymmetry* is the foils has less Z than the drain, and the *twisted pair* VS strait drain *null* any remaining asymmetry.
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Last edited by Esperado; 27th January 2013 at 10:55 PM.
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Old 27th January 2013, 11:19 PM   #33742
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Originally Posted by vacuphile View Post
Steve, that word probably got to do with approximately the part I am sitting on right now, with 'retentive' added.
No, that would be two words.

Quote:
I wasn't clear enough, as in my case I also need to design for large cable runs >25 meter to active speakers with classD amps and switched power supplies, so it is also a matter for EMR not radiating out.
Greater than 25 meters? What, are you wiring up a small concert hall or something?

se
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Old 28th January 2013, 12:20 AM   #33743
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Originally Posted by Triodethom View Post
I really enjoyed his remark "electrons don’t care and they don’t read schematics!", which may have been a quote from D. Gerke and W. Kimmel in the references.

Video has changed since 2005, (in ways that only increase the importance of low inter-equipment "ground" voltages), and jneutron's thoughts about proximity of AC power and signal wiring has refined my viewpoint, but that's still a terrific paper. And very accessible.

Thanks,
Chris

Last edited by Chris Hornbeck; 28th January 2013 at 12:22 AM.
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Old 28th January 2013, 01:23 AM   #33744
RNMarsh is offline RNMarsh  United States
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I have given talks back to back with B.Whitlock and other talks with ac power designers. [And, worked for years in the ac power field for high power experimental machines.] Anyway, in both cases I thought they knew thier stuff as they did about me. But I never heard anything new... that is to say, something that I had not read or seen in practice elsewhere before.. a generation earlier. His patent(s) not withstanding.
Recycling info is important to do. There are many good technical books on the subject.... Bill W. has foot noted and referred to many of them for his material. He is an excellent teacher of the subject. Thx-RNMarsh
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Old 28th January 2013, 06:50 AM   #33745
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About ground loop problems, and noise induced in connections, the first thing i do, when i build any system, is to find the good AC sens of any equipment, to minimize the Ac leakage between us.
We gone work with a dedicated AC distributor for our Hifi equipment. We need access to the cabling of the AC power plugs in-it.

CAUTION of electric shocks: isolate yourself, and do not touch any chassis or wire with hands, while you do it. When you do any wiring operation, unplug the distributor from the wall. Remember you play with your life, verify there is not AC twice before to touch anything including chassis. Each time you will connect the signal cables between equipment, disconnect the distributor from the wall.

Remove the earth wire from the AC plug in the distributor where you will connect your preamp and plug the power of your preamp (or the equipment where all signal connections comes in) in the distributor,.
Measure the Voltage between it and the disconnected earth wire. Change the sens of the 2 AC wires in your distributor for this plug, and measure again. Chose the sens where you have less AC leakage between the earth pin and the earth wire ( reading your voltmeter). Reconnect the earth of this plug in your distributor and mark the plug for this device.
Now, plug AC of your second equipment, don't connect the signal cables, while disconnecting the earth wire inside the AC distributor. Measure the leakage between the pin earth and the wire's earth (or between the chassis) find the best AC sens to minimize the voltage between them. Reconnect the earth wire in your AC distributor. Mark your plug for this device. disconnect the distributor from the wall.
Connect the devices and connect the signal cords between them. reconnect the distributor in the wall.
Do the same for each device, one after the other.
When everything is connected and grounded, you can do the same operation between the main earth and the earth of the wall outlet.

Now your system is optimized for the less AC leakages between the equipments, means signals as clean as possible in your situation.
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Last edited by Esperado; 28th January 2013 at 07:06 AM.
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Old 28th January 2013, 07:11 AM   #33746
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An other and safer method to do it is to use 2 distributors.The second will be plugged in the first one, in such a way that the power AC wires will be inverted. You will plug you devices alternatively in each distributor, and measure the leakages between the chassis to chose the AC distributor with the less leakage for the device.
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Old 28th January 2013, 01:50 PM   #33747
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Originally Posted by Esperado View Post
Again, the foil is very thick and low-z and in contact with the drain all the way. The drain is only here to help welding, strait, while the two wires are twisted. Please, get a sample and measure before to give false inputs. Really no need to argue endless, are-you working for a challenger manufacturer ?
Actually, what he stated was correct. Indeed, it is not possible to have a twisted diff cable where the shield centroid is coincident with the signal centroid at audio frequencies. As one climbs into the Mhz area, the hf will try to overlap the centroids, but that requires conductivity around the entire cable. Foil may be adequate, I don't know. However, the twisted pair will share a common centroid by integration along the cable length.

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Originally Posted by Esperado View Post
All this controversy is like talking about -140dB distortion.
If you were trying to troubleshoot a pin one problem in an audio system, it would be more significant than -140dB.
Quote:
Originally Posted by Esperado View Post
Now, the reason why this cable does not suffer from the 'current centroid asymmetry* is the foils has less Z than the drain, and the *twisted pair* VS strait drain *null* any remaining asymmetry.
Actually, as described, the shield current would redistribute at hf, so signal containment in both directions (inward or outward) would be complete.

jn
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Old 28th January 2013, 02:38 PM   #33748
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Quote:
Originally Posted by Esperado View Post
About ground loop problems, and noise induced in connections, the first thing i do, when i build any system, is to find the good AC sens of any equipment, to minimize the Ac leakage between us.
We gone work with a dedicated AC distributor for our Hifi equipment. We need access to the cabling of the AC power plugs in-it.

CAUTION of electric shocks: isolate yourself, and do not touch any chassis or wire with hands, while you do it. When you do any wiring operation, unplug the distributor from the wall. Remember you play with your life, verify there is not AC twice before to touch anything including chassis. Each time you will connect the signal cables between equipment, disconnect the distributor from the wall.

Remove the earth wire from the AC plug in the distributor where you will connect your preamp and plug the power of your preamp (or the equipment where all signal connections comes in) in the distributor,.
Measure the Voltage between it and the disconnected earth wire. Change the sens of the 2 AC wires in your distributor for this plug, and measure again. Chose the sens where you have less AC leakage between the earth pin and the earth wire ( reading your voltmeter). Reconnect the earth of this plug in your distributor and mark the plug for this device.
Now, plug AC of your second equipment, don't connect the signal cables, while disconnecting the earth wire inside the AC distributor. Measure the leakage between the pin earth and the wire's earth (or between the chassis) find the best AC sens to minimize the voltage between them. Reconnect the earth wire in your AC distributor. Mark your plug for this device. disconnect the distributor from the wall.
Connect the devices and connect the signal cords between them. reconnect the distributor in the wall.
Do the same for each device, one after the other.
When everything is connected and grounded, you can do the same operation between the main earth and the earth of the wall outlet.

Now your system is optimized for the less AC leakages between the equipments, means signals as clean as possible in your situation.
I don't know how you do things over in France, but over here, you should NEVER change the sense of the AC mains hot and neutral.

They should always be wired like this:

Click the image to open in full size.

se
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Old 28th January 2013, 02:39 PM   #33749
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Finally, some common sense about ground leakage! That is another 'tweak' that we did with the Parasound JC-1 when we designed it. As it has multiple transformers, we oriented each transformer to be lowest leakage when the power cable was connected normally. This is different from the HCA3500, that did NOT have properly oriented transformers. It was one of the first things that we changed.
Just another 'tweak' to get best performance. Interestingly enough, Hi Fi books from the '50's used to suggest the same thing. It was easier then, with just two leads, and no 3'rd wire ground, at the time.
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Old 28th January 2013, 02:55 PM   #33750
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Originally Posted by Steve Eddy View Post
I don't know how you do things over in France, but over here, you should NEVER change the sense of the AC mains hot and neutral.

They should always be wired like this:

se
Especially when the electricians have wired your lab benches with alternate phases of 220.

What is the practice with those two round prongs that go in either way?
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