PMA said:
I did measurements of post-arc currents in SF6, initial transient recovery voltages across UHV breakers after SLF (short line fault) interruption and dielectric breakdowns in SF6 and vacuum breakers
Neat stuff, sf6 eh? How fast were the rise and falltimes? Under a nano?
They use it here for a 14 megavolt vandy..I don't go near it..
Cheers, John
jneutron said:
In fact, beyond our measurement limits
During dielectric breakdown, voltage across breaker collapsed from say 240kV to zero during time shorter than 100 nanoseconds (influenced by test circuit reactances as well). A lot of energy in a test circuit and generator (50kA breakers), a lot of ultrafast oscillations and sometimes damages - you can imagine. Generators for impulse voltage MV wave have no energy compared to this, just spark gap discharge.
Ah, ok..Wavebourn said:
I would certainly agree with that.
I'm sure MH had beliefs when he wrote his article in '85. It's unfortunate he chose not to peer review it, as it would not have withstood scrutiny, especially the test setup. Doesn't make him a bad guy..I certainly look up to and admire him..
But when anybody makes a claim or invokation, it must be fair game for discussion. Attack the concepts, not the person.
MH's calculation of radial velocity of 2.93 meters per second is consistent with reality, but to invoke this velocity in the axial direction was inconsistent with the equations. 2.93 is the speed inwards, where a TEM wave dissipates. Axially, it would mean that I could send a truncated 50 hz sine down a 100 meter long coax, shut it off, disconnect it, and then run to the other end of it, and watch residual??? Nah, with a prop velocity of 75% C, I don't think it's a very close call.. buuut, then again..back in '85 I was in much better shape....hmmm.
Cheers, John
Re: re re re
In a wire pair, I've seen no upper limit to speak of.
When I was developing a TRR methodology for my employer back in '82, I used a tek type 109 pulse generator, using a charged line as the source. It drove a 50 ohm cable, and rise/fall were about 250 picoseconds. (I had never heard before that a mercury wetted reed had such speeds of connect and disconnect.)
No matter what kind of cable I drove, it still had the 250 pico rise and fall at the other end.
Made for an awesome TRR setup, watching 4148's recover in a nano and a half..hard..whoa..
Cheers, John
albin said:
In a wire pair, I've seen no upper limit to speak of.
When I was developing a TRR methodology for my employer back in '82, I used a tek type 109 pulse generator, using a charged line as the source. It drove a 50 ohm cable, and rise/fall were about 250 picoseconds. (I had never heard before that a mercury wetted reed had such speeds of connect and disconnect.)
No matter what kind of cable I drove, it still had the 250 pico rise and fall at the other end.
Made for an awesome TRR setup, watching 4148's recover in a nano and a half..hard..whoa..
Cheers, John
jneutron said:
The problem is, to recognize is it a concept, or a belief. When somebody believes that some certain topology gives the best possible results, but listening tests are still don't satisfy him, he is trying to search for causes of errors outside of his perfect creation, such as dielectrics, shields, wires, etc... Somebody may just change a wire being in good mood and hears as if it sounds better. Now, people who believe in science search for an answer, why... There must be some scientific explanation, right?! Now, here it is! The Article! He is satisfied, feels good, he Knows The Truth!
However, if it is just a concept you may discuss it without hurting of his feelings... But when it is a belief any doubt causes a pain. Bringing some information, discussing details, you are hurting his feelings, despite they are caused by belief in science, that does not look like a religious belief! But it hurts the same...
It is difficult to discuss stereo reproduction, because stereo images can't be taken by a photo camera and posted to compare results...
Wavebourn said:
So then your are embracing zero discussion? Never question a statement simply because it may be a "belief".
Science does not work like that. Present a testable hypothesis, then test it. It's that simple.
ALL of the concepts and understandings we currently have will eventually be proven either incorrect, or incomplete.
They will be proven incorrect by the use of testable hypo's...they will never be proven wrong by an untestable belief.
If you (third person designation of course) wish to invoke magic that cannot be proven as nonexistent, do not expect others to sit idly by saying "hey, he believes is, therefore we cannot discuss it or bring actual proof to the table which shows otherwise..
ps...for amplifier topologies and "sound", I would be stupid NOT to defer to the experts in such matters...John Curl is one of those experts for whom I would certainly trust in such matters.
That does not mean I have an unswerving belief that all he says is gospel..ESPECIALLY on a topic that I have a "modicum" of understanding and expertise..
Cheers, John
Wavebourn said:
No, I disagree. It is easy to discuss stereo reproduction.
My point is, the audio industry has not yet undertaken the understanding of the specific parameters required for localization.
Many recordings still have IID positioning without ITD (pan pot), or a combo of IID and ITD which is inconsistent with human localization.
How many amplifiers have been measured for accuracy of IID and ITD at the level humans are sensitive to? NONE.
And people wonder why designers such as John Curl have to go by listening as opposed to test equipment??
I don't wonder. I believe he's using the best tool for the job..
Cheers, John
One of my great regrets is giving away my 1963 vintage Lumitron sampling scope. It had the same charged line generator and used a solid air line sampling head with GE tunnel diode time base and 6CW4's to capture the input on their inter-electrode capacitance. All discrete and probably every exotic semiconductor made at the time.
scott wurcer said:
Every EE should be forced to learn how all that old stuff worked, it amazes me.
What, you miss sitting in a dark room to look at sub nano risetimes??
First sampler for me had the PFN's, but pushed a bridge input..solid state microwave diodes of some type..
The current stuff is so boring, eh? Specially when you can transfer the sigs by usb....
Cheers, John
john curl said:
Hey, didn't you mention somewhere in this thread, that you were an expert in diode switching?
What'd ya think of the HP 214B as opposed to the HP 214A?
I really hated the auto-load detect system, it always wanted to cut out at juuuust the right level for the -1.5 amp drive current...
What a PITA...
That's why I switched to the TEK 109. Needed it for the (fast) epi product my employer was doin R&D on.. the 214 ran about 10 nano risetime, and I refused to test 15 nano product with a 10 nano rig..(course, the 109 was about 20 years old at the time)
Cheers, John
scott wurcer said:
Heh... Tunnel diode.
That ham radio jammer in a slipper I spoke about few pages before used exactly a tunnel diode for a dirty 3.5 MHz generator. There were 3 diodes only, no transistors: a tunnel diode, a 2-base diode (to generate a saw) and a varactor diode (to jam the whole band).
Wavebourn said:
Heh... Tunnel diode.
That ham radio jammer in a slipper I spoke about few pages before used exactly a tunnel diode for a dirty 3.5 MHz generator. There were 3 diodes only, no transistors: a tunnel diode, a 2-base diode (to generate a saw) and a varactor diode (to jam the whole band).
Yes amazing things. I forgot to mention the sampling was done by 4 snap diodes in a bridge one leg soldered to the center conductor through two holes drilled in the hard line and the opposite leg soldered directly to the 6CW4 grid.
Wavebourn said:
I don't think anybody knows.
But the point I would make is, current SOTA does not embrace the parameters we humans use to localize an image..We have no piece of test equipment that can find a 5 or 10 uSec sibilance shift interchannel, when a complex set of waveforms is present. (you know, like..."music")
As such, if Cheryl's vocal sibilance is driven to the right 15 degrees spacially with respect to the rest of her voice, how would I measure that? Nothing I am aware of can do this, as it can be a temporal shift of tens of microseconds, Interchannel level shift tenths of a dB, or heaven forbid, a result of channel dither due to a driver position/velocity modulation. (especially a single driver system).
John Curl uses his ears for that stuff..
I believe that is a good call..
Uh oh, a "belief"
..sheesh..Cheers, John
scott wurcer said:
Aha...sounds like the same circuit I had. The t-line had equal and opposite pulses on top and bottom, two resistors for current/voltage limit, and opposite the grid was the input.
I use that circuit occasionally now, but just use it as a limiter.. the diodes go reverse if the input signal exceeds the V/R limit of the up and down resistor...uses the TFR of the diodes instead of the TRR. Saves on opamps....
Cheers, John
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