hi ,,,An old book with title: "The recording and reproduction of sound" by Oliver Read ,Editor, Radio and Television News and radio electronic Engineering ,1952 Indiana USA, wrote about this phenomenon: Magnetization of tubes. " Glass tubes of a given type show more individual variation in hum level than metal tubes The British journal WIRELESS WORLD has reported that this phenomenon is associated with permanent magnetization of the tube elements, which seems to increase the hum level in a way not yet understood. The remedy is demagnetization with a gradually removed 50-60 cycle field, the same as jewelers do with watches.The winding of an old power transformer, removedfrom the core, can be used for a demagnetizing coil.Connect the secondary across the 115 volt line{ using series resistance if necessary, to keep it from gettingtoo hot} insert the tube, then slowly withdraw it.'' THANKS
PRIDE AND PREJUDICE...
Hi,
Did I say I've never tried it? Don't think so.
However, by just pulling the tubes in and out if their sockets you can already hear a difference unless the pins are treated with a contact enhancer...perhaps?
See, I don't have to pull out tubes and start looking for a magnet, being notoriously lazy, I just run that CD and, voila...The system is now demagnetized...including the tubes.
Psssstttt....Did you know that even CDs themselves benefit from the occasional demagnetization?
BTW, the cause of the problem is often paramagnetic remanance, not magnetism per se.
Happy now?
Hi,
Did I say I've never tried it? Don't think so.
However, by just pulling the tubes in and out if their sockets you can already hear a difference unless the pins are treated with a contact enhancer...perhaps?
See, I don't have to pull out tubes and start looking for a magnet, being notoriously lazy, I just run that CD and, voila...The system is now demagnetized...including the tubes.
Psssstttt....Did you know that even CDs themselves benefit from the occasional demagnetization?
BTW, the cause of the problem is often paramagnetic remanance, not magnetism per se.
Happy now?
Riiiiiiiiight.
Then in that case, please tell me the difference between whatever they have on the CD, and the random nature of music, or even the regular rythm of a sine wave? (Heck, even a DC offset is averaged to zero in a typical AC-coupled amplifer. 2Hz squarewaves make interesting viewing if you have an LF instability!)
Tim
Then in that case, please tell me the difference between whatever they have on the CD, and the random nature of music, or even the regular rythm of a sine wave? (Heck, even a DC offset is averaged to zero in a typical AC-coupled amplifer. 2Hz squarewaves make interesting viewing if you have an LF instability!)
Tim
Frank my pins and sockets are keep clean as a whistle, with cleaner/enhancer using small dental brushes, so it`s definatly not that what i`m hearing.
Try again.
You still have`nt said you`ve tried it, just stated that you have`nt stated you have`nt.
( wow! that was a voodoo sentence)
Cheers George
MR. OBNOXIOUS REACHING CURIE POINT?
Hi,
Do you always come to conclusions this way?
What doesn't work and what part is it you don't understand?
I already said you can find out how demagnetisation works both in threads here on the forum and elsewhere.
So what is it you want ME to prove that's already been proven by others?
Cheers,
Hi,
Do you always come to conclusions this way?
What doesn't work and what part is it you don't understand?
I already said you can find out how demagnetisation works both in threads here on the forum and elsewhere.
So what is it you want ME to prove that's already been proven by others?
Cheers,
SEARCH ENGINE PICKY ON USERS?
Hi,
I want a million green ones too....
Seems I have better karma...
LOCAL SEARCH
MC CARTRIDGE DEMAG
PHOTONS FOR YOU....
If, after carefully reading all this material you still don't see how putting a file on a CD and playing it back replaces half of the ancilliaries normally needed, I'll just throw in the magnet errr....towel.
Enjoy,
Hi,
I want a million green ones too....
Seems I have better karma...
LOCAL SEARCH
MC CARTRIDGE DEMAG
PHOTONS FOR YOU....
If, after carefully reading all this material you still don't see how putting a file on a CD and playing it back replaces half of the ancilliaries normally needed, I'll just throw in the magnet errr....towel.
Enjoy,
Sorry Frank, but I see no evidence in there. I fully read all of them. No explanation for why any particular form of noise is preferred over the rythmic noise known as music, nor the reasoning to get there, that is, whether or not such materials that signal paths contain can actually take a set, or burn in at different frequencies, etc. Not to mention why one would think a static magnetic field offset on a wire would affect AC or DC signals carried in it, nor why one wouldn't simply fix the whole deal by passing the amplifier/inter\\\\PATCH CABLE 
through a degaussing coil, etc....
Oh, and above all... why doesn't the very movement of the coil against its magnet "degauss" (which as we all know is "re-gauss", because it is in the static field of said magnet
) the coil continuously while playing?
Tim
through a degaussing coil, etc....Oh, and above all... why doesn't the very movement of the coil against its magnet "degauss" (which as we all know is "re-gauss", because it is in the static field of said magnet
) the coil continuously while playing?Tim
Time for me to have another little go, tv tubes are tubes after all, they have automatic de-gausers that de-magnetises the tube every time it`s switched on, if that stops working (and i have seen the results) of a tube that`s magnetised, it`s very scary, why then only once every two months de-magnetise our tubes.
Especially when it helps the sound improve.
Cheers George
Especially when it helps the sound improve.
Cheers George
CRT degaussers specifically demagnitize the shadow mask, a part not present in amplifier tubes. A magnetized shadow mask affects color purity because the electron beam hits the wrong colored phosphor dots, also not present in amplifier tubes. It doesn't follow that since CRTs are adversely affected by magnetization, then amplifier tubes necessarily would be as well.
Well let's think about TV/Monitor tubes:
A thin beam of electrons is fired from the back of the tube to the front. In the case of my computer monitor that seems to be about 40cm. A very long way compared to a regular amplifier tube.
The electrom beam has to hit a very small spot, the pixel, even worse it has to hit the right point within the pixel to hit the correct red, green or blue phosphor for that beam. So we need an accuracy of 0.3mm say. This about 0.05 percent of the traveled distance.
Now any magnetic field component perpendicular to the beam direction will deflect it. What we find is that very small fields will move the beam into the wrong colour phosphor and upset the image colour. I once had a large computer monitor that would drastically alter in image colour when rotated throug 90 degrees on my desk. This is only due to the change in alignmnet with the earths magnetic field !
Now lets look at regular amplifier tubes:
The distance the electrons travel is about 100 times smaller.
The electron's target, the anode, is huge. We are looking at an area thousands of time bigger than a pixel.
Not only that, generally the anode actually surrounds the cathode. It's not just a plate as drawn in the circuit symbol, it is a tube. So even if the electrons are deflected it would be very hard for them to miss their target.
So at this point I would guess that any stray static field within the tube or near by would have an effect that is vanishingly small compared to all the other manufacturing tolerances in tubes or aging effects.
However as I said before I have done an experiment in school where a coil is wound around a tube and the current through the coil causes a field in the tube. When that field is big enough the tube cuts off as the electrons assume circular orbits between cathode and plate and never reach the plate. But we are talking huge fields here.
So if anyone wants to check this, just wind a coil around a tube and pass a couple of amps through it. Use a compass near by to detect the resulting magnetic field. Turn the current on and off and try to hear a change in your amplifiers sound. I think I am going to try this myself tonight.
If you hear a difference you will want to degauss your tubes.
And perhaps align your amp correctly with the earth's field
Happy experimenting.
Here is some nice text and an experiment about electrons and magnetism:
http://www.drchaos.net/drchaos/Whit/Lab_Manual/node20.html
A thin beam of electrons is fired from the back of the tube to the front. In the case of my computer monitor that seems to be about 40cm. A very long way compared to a regular amplifier tube.
The electrom beam has to hit a very small spot, the pixel, even worse it has to hit the right point within the pixel to hit the correct red, green or blue phosphor for that beam. So we need an accuracy of 0.3mm say. This about 0.05 percent of the traveled distance.
Now any magnetic field component perpendicular to the beam direction will deflect it. What we find is that very small fields will move the beam into the wrong colour phosphor and upset the image colour. I once had a large computer monitor that would drastically alter in image colour when rotated throug 90 degrees on my desk. This is only due to the change in alignmnet with the earths magnetic field !
Now lets look at regular amplifier tubes:
The distance the electrons travel is about 100 times smaller.
The electron's target, the anode, is huge. We are looking at an area thousands of time bigger than a pixel.
Not only that, generally the anode actually surrounds the cathode. It's not just a plate as drawn in the circuit symbol, it is a tube. So even if the electrons are deflected it would be very hard for them to miss their target.
So at this point I would guess that any stray static field within the tube or near by would have an effect that is vanishingly small compared to all the other manufacturing tolerances in tubes or aging effects.
However as I said before I have done an experiment in school where a coil is wound around a tube and the current through the coil causes a field in the tube. When that field is big enough the tube cuts off as the electrons assume circular orbits between cathode and plate and never reach the plate. But we are talking huge fields here.
So if anyone wants to check this, just wind a coil around a tube and pass a couple of amps through it. Use a compass near by to detect the resulting magnetic field. Turn the current on and off and try to hear a change in your amplifiers sound. I think I am going to try this myself tonight.
If you hear a difference you will want to degauss your tubes.
And perhaps align your amp correctly with the earth's field
Happy experimenting.
Here is some nice text and an experiment about electrons and magnetism:
http://www.drchaos.net/drchaos/Whit/Lab_Manual/node20.html
I don't know what the big argument is. The results of demagnetization of tubes have been measured, with a decrease in hum voltage and noise figure. After some thought, I've realized that a even a small magnetic remnance in the cathode could couple the alternating magnetic field of the heater to the electron space charge, thus increasing hum levels. Obviously this only applies to AC-heated filaments, although some noise from a regulated DC supply could be transferred. In the case of overall noise figure, a magnetized cathode could cause a greater randomization of shot noise, thus increasing RMS values.
John
John
Shot noise (in a negative-grid triode) is dependent on the temperature of the cathode and the Gm of the tube in question and bandwidth, specifically, it is directly proportional. The filament may also contribute some thermal white noise because it is essentially a resistor, and with the hypothesis, once coupled to the space charge it becomes part of the overall circuit.
Secondly, what is the magnitude of the remanence in a pure nickel cathode (not so mention the emmissive coating) and how much is too little? I haven't seen any real figures from you, Tim, not even ballpark. I only advanced a hypothesis, and a knee-jerk naysay rooted in audiophilephobia hasn't swayed me away from it.
I'm open to any scientific proof otherwise or even a real theory backed by some hard numbers and mathematical equations. The fact remains that the results of demagnetization are MEASUREABLE and I have yet to read anything from you that actually disputes this fact, other than that you are simply in dispute.
John
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.