This is across a .1 ohm resistor. It is from my power supply bits I showed here a few years ago. It shows the sudden switch on of current to charge the filter capacitor and then the slow tail off as the capacitor charges the voltage out of the transformer also rises due to the decrease in load.
Bits and pieces, surge charging currents may be interesting, but not so much, as we care about output power or supply rails voltage. Both is easily measurable even for sudden step signal level changes. So, to me, this is another example of FUD, unsupported by real reasonable data. I think I have used the term FUD for the 1st time, but now it deserves it. No normal amplifier will have troubles with fuse resistance. Fuse is chosen just to fit to the amp power level. What is real is the reduced value of supply rails voltage due to constant high output power, capacitors cannot be charged to keep maximum value then. This is a fact and fuse voltage drop is a FUD compared to this fact.
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To confirm you are saying the peak current is 1.6A and I believe this is steady state.
A quick check of my samples on hand- 1A fast blow .250 Ohm, 1A time delay .650 Ohm. The .650 Ohm is a little surprising. Still less than a volt at 1A. Also higher than the Littlefuse datasheet 3AB/3AG (6.3x32mm) Cartridge Fuses - Littelfuse . (So much for Radioshack) read through the datasheets to better understand the time vs. blow relationship. Basically a 1A fuse will support 1A for at least 4 hours. A fast blow 1A would pop at 2A in 15 seconds max. A slow blow would be at least 5 seconds and as much as 30 seconds. Hopefully your power supply is fully charged in less than 5 seconds.
A quick check of my samples on hand- 1A fast blow .250 Ohm, 1A time delay .650 Ohm. The .650 Ohm is a little surprising. Still less than a volt at 1A. Also higher than the Littlefuse datasheet 3AB/3AG (6.3x32mm) Cartridge Fuses - Littelfuse . (So much for Radioshack) read through the datasheets to better understand the time vs. blow relationship. Basically a 1A fuse will support 1A for at least 4 hours. A fast blow 1A would pop at 2A in 15 seconds max. A slow blow would be at least 5 seconds and as much as 30 seconds. Hopefully your power supply is fully charged in less than 5 seconds.
Demian,
Run 1 amp through the slow blow fuse and measure the voltage drop if you can.
Over the weekend I will dig up my data on a fuse in a clean AC line loaded by a full wave bridge, capacitor and load.
We could discuss what I^2 T means both for fuse actual ratings and the effect of just I vs R. Fuses are definitively not low tempco resistors.
Pavel,
In a properly designed audio amplifier fuses should not make a difference particularly at 230 VAC mains. But when a fuse current rating goes down the nonlinear influence goes up exponentially. This does affect many mid-fi consumer products.
The issue was can changing a fuse change the perceived sound quality. The answer is it can but it should not. I would never suggest changing an AC mains fuse from the rated value.
However I do recommend buying name brand fuses.
Run 1 amp through the slow blow fuse and measure the voltage drop if you can.
Over the weekend I will dig up my data on a fuse in a clean AC line loaded by a full wave bridge, capacitor and load.
We could discuss what I^2 T means both for fuse actual ratings and the effect of just I vs R. Fuses are definitively not low tempco resistors.
Pavel,
In a properly designed audio amplifier fuses should not make a difference particularly at 230 VAC mains. But when a fuse current rating goes down the nonlinear influence goes up exponentially. This does affect many mid-fi consumer products.
The issue was can changing a fuse change the perceived sound quality. The answer is it can but it should not. I would never suggest changing an AC mains fuse from the rated value.
However I do recommend buying name brand fuses.
Yes the 20mm are definitively better and Schurter among the best. Ever try a Bel fuse? Or an unnamed cheaply? Interesting the 10/1 difference between yours and Demians.
If you want to get a modestly scary result following I^2T try 3 amps at a 10% duty cycle, 120 hertz repetition rate and measure the voltage drop with a 1 amp time delay fuse. A more realistic simulation of maximum safe load.
BTY they make adapters to put 20mm fuses in 3AG size holders. A safe way to reduce any fuse nonlinear contributions.
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Actually, he is going by the numbers. Unfortunately, he is thinking haversine peak currents. All a higher resistance fuse will do is broaden the current waveform, dulling the peaks but having very little effect.
jn
Did you miss a theory lesson ?.
Adding extra flyback diodes or series resistance in series will alter the relay coil current decay time/armature attraction and alter contacts timing.
Telephone Switches
These relays were called toe end slug or heel end slug relays and were required to implement timing functions in earlier relay based telephone systems.
Dan.
Seems there is a bit of confusion about fuses. It takes work to blow a fuse. In high school most probably learned work is Force time Distance. It also is Power multiplied by Time.
Meaning the work to blow a fuse can be expressed is I x E x T. Where I is current measured in Amperes, E is electromotive force measured in Volts and T is time usually measured in seconds.
As most here know I^2xR also equals power, so fuses are often rated by I^2 x T assuming the resistance stays about constant. Thus a 1 amp fuse should carry 1,000 amps for a microsecond! This does not result in damage to the protected components that are ohmic or follow Ohm's law. It is why things like semiconductors are difficult to fuse.
Now fuses don't quite follow Ohm's law as they heat up most increase a bit in value thus increasing the voltage across them resulting in absorbing more power and lessening the time required to open.
I had three different types of 1 amp time delay fuses in the 3AG size in my stock. Testing them at test currents for .025 seconds caused none of them to fail. (Not surprising.) The worst one went from .106 ohms cold to .247 ohms at 1 amp and to 1.034 ohms at 2 amps. I did not have a power supply handy that could deliver 5 amps. It should not surprise anyone that even without any additional rise in resistance at 5 amps for .025 seconds capacitor charging time that would account for an 8.5% loss of power at a line voltage of 120 VAC into a load that responds to the line's peak voltage. Now an RMS volt meter would not show anything like that AC mains loss as this is clipping only a tiny amount of the peak.
As most AC power lines are already distorted the peak level charging time would increase and the effective loss would be less. Or if you want to test for theoretical losses due to fuse losses you must have a clean AC power line or at the very least measure the power line distortion. An easy way to do this is to measure the line voltage with a peak responding RMS reading meter and a true RMS meter. The peak responding meter will show a lower voltage. Failing that the simple test is to use a diode to charge a capacitor to peak voltage. Without any distortion due to electronic loads at 120 Volt AC power line should read 170 volts DC. (Of course if you measure the line voltage without using a true RMS meter you shouldn't see a difference!)
The actual peak audio amplifier power when it has a linear power supply will be reduced by AC mains line distortion. That is why when high power amplifiers are tested the line voltage is stabilized and measured with a peak responding meter.
This is pretty much no longer a problem for my large systems as virtually all the power amplifiers have a power factor corrected switching power supply.
So it is not unreasonable as originally expressed for an audio amplifier to perform differently with the fuse bypassed. It might sound different and would certainly be unsafe. A good compromise would be to change the fuse to one of the lower resistance name brand ones in the 5 x 20 mm package with the same current ratings.
When I did my power supply tests I used a clean sine wave from a high power amplifier to drive all the devices under test. It also allowed me to test at both 50 and 60 hertz.
Meaning the work to blow a fuse can be expressed is I x E x T. Where I is current measured in Amperes, E is electromotive force measured in Volts and T is time usually measured in seconds.
As most here know I^2xR also equals power, so fuses are often rated by I^2 x T assuming the resistance stays about constant. Thus a 1 amp fuse should carry 1,000 amps for a microsecond! This does not result in damage to the protected components that are ohmic or follow Ohm's law. It is why things like semiconductors are difficult to fuse.
Now fuses don't quite follow Ohm's law as they heat up most increase a bit in value thus increasing the voltage across them resulting in absorbing more power and lessening the time required to open.
I had three different types of 1 amp time delay fuses in the 3AG size in my stock. Testing them at test currents for .025 seconds caused none of them to fail. (Not surprising.) The worst one went from .106 ohms cold to .247 ohms at 1 amp and to 1.034 ohms at 2 amps. I did not have a power supply handy that could deliver 5 amps. It should not surprise anyone that even without any additional rise in resistance at 5 amps for .025 seconds capacitor charging time that would account for an 8.5% loss of power at a line voltage of 120 VAC into a load that responds to the line's peak voltage. Now an RMS volt meter would not show anything like that AC mains loss as this is clipping only a tiny amount of the peak.
As most AC power lines are already distorted the peak level charging time would increase and the effective loss would be less. Or if you want to test for theoretical losses due to fuse losses you must have a clean AC power line or at the very least measure the power line distortion. An easy way to do this is to measure the line voltage with a peak responding RMS reading meter and a true RMS meter. The peak responding meter will show a lower voltage. Failing that the simple test is to use a diode to charge a capacitor to peak voltage. Without any distortion due to electronic loads at 120 Volt AC power line should read 170 volts DC. (Of course if you measure the line voltage without using a true RMS meter you shouldn't see a difference!)
The actual peak audio amplifier power when it has a linear power supply will be reduced by AC mains line distortion. That is why when high power amplifiers are tested the line voltage is stabilized and measured with a peak responding meter.
This is pretty much no longer a problem for my large systems as virtually all the power amplifiers have a power factor corrected switching power supply.
So it is not unreasonable as originally expressed for an audio amplifier to perform differently with the fuse bypassed. It might sound different and would certainly be unsafe. A good compromise would be to change the fuse to one of the lower resistance name brand ones in the 5 x 20 mm package with the same current ratings.
When I did my power supply tests I used a clean sine wave from a high power amplifier to drive all the devices under test. It also allowed me to test at both 50 and 60 hertz.
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Still unreasonable, nothing in your prose supports this conclusion, although you conveniently lost on the way that outrageous (audio amplifier 12% power loss due to the fuse) claim you originally made.
It would take quite some effort to design an audio power amplifier with audible changes due to the mains fuse.
I don't recall that the fuse was bypassed, a better sounding one was used but it was only better sounding when it was used together with a different wire which I presume sounded better as well.......I'm losing the will to live again......
We have guys who declare they hear difference if they mechanically rotate the mains fuse of 180° (they say the fuse is directional) in the fuse holder. There is no limit
And there are folks who claim turning around interconnects changes the sound. It actually can be true because in doing so they are wiping the contacts and cleaning them.
One of the old tests on televisions under warranty was before going on a service call to ask the customer to try pulling out the AC plug, turning it over and plugging it back in to see if that solved the problem. Frequently they would respond that it did.
Saved a lot of service calls for dead televisions that were just unplugged.
So changing a fuse can have an effect, particularly if it was failing and increasing in resistance.
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