Depends a lot of the time it is (day or night), the day of the week, and if my wife is using the vacuum cleaner.
More sériously, hiss of tapes was a help in the good old analog times to build better consistent mixs. Using-it as a floor reference.
Dear, look how this recording looks great !
Any genealogical connexion with Neron ?
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Max isnt joking; lots of fires near me in east london tonight - went for a midnight drive along Bethnal grn road and up Hackney road and there were gangs running around everywhere, burning bins and carrying all sorts of stuff.
Seems that Police were lying about the incident in Tottenham where the man was shot and it amazes me how completely out of touch our politicians are
Seems that Police were lying about the incident in Tottenham where the man was shot and it amazes me how completely out of touch our politicians are
Yes. Almost literally. They're all on holiday. Well, in fairness to Boris, he said yesterday early afternoon he was coming back (so he'll have made that decision early yesterday morning).
I'm a little concerned about a girl I know in north London. Stupid really, she's no fool (understatement of the century). Still. You do, don't you?
I'm a little concerned about a girl I know in north London. Stupid really, she's no fool (understatement of the century). Still. You do, don't you?
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I have.
Statements like this:
""It is worth noting that a cable will never act as a true transmission line with a defined (and maintained) Zo unless its source and load impedances are equal to the line impedance.""
Tell me a whole lot about what a person understands...or doesn't.
Cheers, John
I have certainly stated such.
Agreed. Seeing the steps allows for visualization of what is happening.
Implies?? It demands.
As I said, using a higher load z in the simulations doesn't help at all. For speakers, it is a rarity that the load is higher than the line across the audio bandwidth. And, the resultant simulation only shows lots of hf stuff at line resonance which far exceeds human capabilities as well as driver reluctance path capability. C'mon, it's iron for goodness sake.. Unless you're using 1 mil thick laminations, this kind of high speed stuff gets dissipated.
It is very important to understand the gradual buildup concept. A transmission line can only transfer AT IMPEDANCE, energy at it's prop velocity. In other words, if the line is 50 ohms, only signal which has the relationship V =50*I will propagate at the line velocity. For a low z speaker, the current in the load can only build up as a result of multiple reflections between the load and the source.
Why are you worried about dispersion?? Remember, while one is using a fast rise to view the structure, we really only worry about the signal which is essentially DC to the cable. By the time the signal has risen to 80/90% of final value, the frequency components of a step function for example, has dropped considerably. Eventually the line drop will be IR only, the capacitance will be fully satisfied.
To examine the rise time. At 5 to 10 uSec risetime, the form gets lost when viewing a 1Khz square.
Cheers, John
I was speaking about the claimed observations. Even with GHz equipment and a 3m piece of ordinary misterminated RG58 you would lose the fine structure long before 200 round trips.
We are certainly on the same channel I think. 🙂 Just go for it, extract the S parameters for the speaker and the cable and do the exact solution.
As a practical matter for a simple lumped L/C which one goes first? Convention is L then C I think.
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Yup.
What are the characteristics of the iron? What is useable as Ls/Rs, and how do they change with frequency? I have yet to find any coil/iron system which is flat, or even easily characterized. I have an air core coil made with litz, that's flat to 20Khz..but all the solid copper coil things proximity all to heck at frequency, and the laminated iron structures totally wipe inductance down and resistive losses up..
Which end do you want to look from?
Where does the prop velocity, and physical length show up in the reflection timing?
The more lumps you put in, the more the physical length gets introduced into the system. Using one of each element ignores prop velocity.
I recall Leseuf used a pi model for a wire in one of the links, but stated that it really made no difference..😕
He completely ignores system settling time..
Cheers, John
Send a sharp pulse bouncing up and down a short poorly terminated cable. Alternatively, look at ringing of the equivalent LRC network. Unsurprisingly, they give similar results (as theory says they should). What has this to do with audio? This is exploring the RF characteristics of the cable. Audio amps don't generate RF, or sharp pulses (except possibly Class D). You can make pretty graphs to impress the uninitiated, but so what? Maybe my ears are defective, but I can't hear 30ns pulses.
Does transmission line theory apply to loudspeaker cables? Of course it does. What does it tell us? It tells us that if short enough they can be treated as lumped LCR networks. This is not denying TL theory, but correctly applying it.
Does transmission line theory apply to loudspeaker cables? Of course it does. What does it tell us? It tells us that if short enough they can be treated as lumped LCR networks. This is not denying TL theory, but correctly applying it.
As I stated, the example with load higher in impedance than the line was a poor one, as ringing is basically the only thing seen.
Do the same with a correct load, and the response is an exponential. This exponential is the system settling time, which is dependent on the relationship between line and load.
The poorly chosen model does indeed to that. Which is why I questioned it.
Nobody has claimed audio amps generate rf in any way, and nobody has claimed you can hear 30 nS pulses...so why say it? Pointing off in the distance does nothing for the discussion.
Cheers, John
There is a reason for the inductor in the output leg of many solid state amplifiers. Looking around with an RF probe does every so often turn up amplifiers that create RF energy sometimes as high as 500 MHz!
So let me claim so audio amplifiers do generate RF! (And some surprising name brands!)
While I do agree with you, it is important to consider the statement within the context of the discussion. DF96 and I both agree that the extremely fast rising edge cannot be created by an audio amp. It is that edge which is being considered.
Jn
Jn
I'll only agree as far as "Should not." I have seen audio power amplifiers with output on the speaker terminal of several volts at one MHz or so. Two out of a batch of 80!
RF out from one amp does affect the others in a system where the speaker cabling shares conduit. (Not the issue under discussion here, but a semi interesting side note.)
I am absolutely sure that absolute statements are always wrong. 🙂
RF out from one amp does affect the others in a system where the speaker cabling shares conduit. (Not the issue under discussion here, but a semi interesting side note.)
I am absolutely sure that absolute statements are always wrong. 🙂
In my book on designing audio power amplifiers I show the impedance presented to the amplifier of a 10-foot length of speaker cable as a function of frequency. While it is true that so-called transmission line effects do not come into play in the audio band because of the lengths involved, it IS true that transmission line effecst come into play at higher frequencies in the low MHz range where an amplifier may still have its feedback active. This can destabilize some amplifiers. Note that we are not just talking about the lumped capacitance of the speaker cable.
I show the impedance for three cases: misterminated open at the far end, misterminated shorted at the far end, and terminated in its characteristic impedance at the far end. The transmission line behavior is obvious. The decent audio quality speaker cable I used was of zip construction, and its characteristic impedance was about 110 ohms.
Different speakers terminate the speaker cable differently at the far end. Sometimes, one might place an R-C Zobel network at the speaker end to help control the impedance.
Sometimes the transmission line behavior of the speaker cable, combined with the speaker "waving in the breeze" can act as an antenna for EMI as well.
Cheers,
Bob
I show the impedance for three cases: misterminated open at the far end, misterminated shorted at the far end, and terminated in its characteristic impedance at the far end. The transmission line behavior is obvious. The decent audio quality speaker cable I used was of zip construction, and its characteristic impedance was about 110 ohms.
Different speakers terminate the speaker cable differently at the far end. Sometimes, one might place an R-C Zobel network at the speaker end to help control the impedance.
Sometimes the transmission line behavior of the speaker cable, combined with the speaker "waving in the breeze" can act as an antenna for EMI as well.
Cheers,
Bob
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