"Actually, as I think you must know perfectly well, the rms voltage of a sinusoidal waveform (its heating power) is 7/10 that of its peak voltage, which is presumably what you are assuming for DC from a faulty amp."
7/10th's is the same as a 30% reduction. That means at least a 30% increase in steady state heat. I say "at least" because we are basing this on a linear sine wave measurement. Using anything other than that can skew the results even further i.e. even greater heat dissipation.
"Furthermore, if the amp goes into oscillation, which is the most likely failure mode, the output will be a square wave, (instead of a sine wave) which has exactly the same power as DC."
This is not "completely" true. A square wave is still AC and will work the driver as it normally would. The only difference is that the average power levels are higher than what one would see with a sign wave. The difference is that due to the driver still working properly i.e. moving fore and aft, you will dissipate energy as both acoustic output and as heat. If the driver has a vented spider or a vented pole piece, the motion of the driver will aid the natural convection of heat away from the voice coil and coil former. This has to do with the pressure changes within the driver itself caused from the fore and aft motion.
When you apply DC to the driver, it locks the driver in one position and holds it there. Depending on the polarity of the DC signal and how it is connected to the driver, it can be thrown out or sucked in. There is no acoustic output to dissipate energy and since the driver is stuck in one position, the natural convection cooling of the driver itself is reduced.
While both will end up causing driver failure, DC will do it faster than clipped AC.
"DC transmits over long distances very efficiently. Better than AC. A lot of research work was done on that technology here in Pittsfield Mass by the General Electric Transformer business."
I wonder if they ever published any information on this based on their test results. I'm sure it would be interesting.
"With either AC or DC long distance transmission calls for voltage of several hundred thousand volts."
Current day AC systems travel for many, many miles using voltage levels that never come close to 100+ KV. While i could be wrong, i think that our local lines operate at appr 24 KV or so.
"You can't have that going into your house!
You can't really have that going through the air either. In times of heavy humidity and the level of current available, the potential for arcing would be too great. Sean
>
7/10th's is the same as a 30% reduction. That means at least a 30% increase in steady state heat. I say "at least" because we are basing this on a linear sine wave measurement. Using anything other than that can skew the results even further i.e. even greater heat dissipation.
"Furthermore, if the amp goes into oscillation, which is the most likely failure mode, the output will be a square wave, (instead of a sine wave) which has exactly the same power as DC."
This is not "completely" true. A square wave is still AC and will work the driver as it normally would. The only difference is that the average power levels are higher than what one would see with a sign wave. The difference is that due to the driver still working properly i.e. moving fore and aft, you will dissipate energy as both acoustic output and as heat. If the driver has a vented spider or a vented pole piece, the motion of the driver will aid the natural convection of heat away from the voice coil and coil former. This has to do with the pressure changes within the driver itself caused from the fore and aft motion.
When you apply DC to the driver, it locks the driver in one position and holds it there. Depending on the polarity of the DC signal and how it is connected to the driver, it can be thrown out or sucked in. There is no acoustic output to dissipate energy and since the driver is stuck in one position, the natural convection cooling of the driver itself is reduced.
While both will end up causing driver failure, DC will do it faster than clipped AC.
"DC transmits over long distances very efficiently. Better than AC. A lot of research work was done on that technology here in Pittsfield Mass by the General Electric Transformer business."
I wonder if they ever published any information on this based on their test results. I'm sure it would be interesting.
"With either AC or DC long distance transmission calls for voltage of several hundred thousand volts."
Current day AC systems travel for many, many miles using voltage levels that never come close to 100+ KV. While i could be wrong, i think that our local lines operate at appr 24 KV or so.
"You can't have that going into your house!
You can't really have that going through the air either. In times of heavy humidity and the level of current available, the potential for arcing would be too great. Sean
>