Fuse bypass switch, WTF!!!
Guess he likes the idea of coming home to a real fire
How about fitting several fuse holders so you can choose different 'audiophile' fuses with the flick of a switch. You could even have a mix of large and small fuse sizes and maybe a circuit breaker
I hope fuse paranoia is not contagious
Guess he likes the idea of coming home to a real fire
How about fitting several fuse holders so you can choose different 'audiophile' fuses with the flick of a switch. You could even have a mix of large and small fuse sizes and maybe a circuit breaker
I hope fuse paranoia is not contagious
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Because it is not about objective performance - it is about creating a convincing illusion.
You can be ignorant on amp design but a genius in creating a convincing illusion.
Jan
More, courtesy of silly me.
Spent a bit of time over the last week “researching” fuseholders. To be clear, as I’m working on a CERTAIN amplifier and am talking mainly about its fuseholders that “house” the 3AG size (1/4” x 1-1/4”) fuses common in most of the audio US equipment made in the last 50? years. Also referring to what seems to be universally called “panel mount”- ie they mount in a single “D” hole, around 1/2” diameter with a flat on one side so it can’t turn when mounted in the hole.
I started by looking in my fuse holder “junk box” and compared the maybe 4 different styles I had there. These holders, made predominately by Littlefuse / Bussman / et al (in the US) seemed to be the style that has a cap which “holds” one end of the fuse, and affixes to the body by a “bayonet-style” (quarter turn) “lock”. Turns out that the cap of the fuseholder on the amp I’m experimenting with does not have quarter-turn lock but instead screws into holder – don’t know the manufacturer or type (it’s 25 years old).
The back of the “typical” holder has a spring which pushes a rear contact up against the back of the fuse, which then pushes the fuse up against another contact inside the cap. So in effect when the cap is in place, the fuse is “spring loaded” against a front and rear contact. The rear contact seems to “universally” exit the rear of the holder and become the attachment point for a wire connection via either solder or crimp-on connector. The front contact, being in the removable cap, makes “friction contact” with a ring around the holder base which has integral tab or attachment point for the other wire connection to the outside world.
Now all fuses, have a metal “cup” on each end which, implies quite a bit of surface area that a holder COULD contact. However, some of the holders only seem to make minimal contact against (a portion of) the top/bottom of the fuse cup; and remember that this contact is held/made via a spring. Some of what I will call the “better” holders actually have a separate metal “sleeve” that encircle the fuse cups, which in my book add “contact area” – certainly a good thing in my estimation. The other thing that I noticed is that the front “outside world” connection tab on some fuseholders is thinner ( read “puny” and flexible) in contrast to others.
So should I give a **** about any of this? Well I do. This holder is on an amp that supposedly can put out up to 600 wpc into 4 ohms. “Stock” power cable on the unit 14AWG. The power switch has good “wiping action” contacts (I checked). Under normal operation, current consumption can vary all over the place. In this situation, if there is a “weak link” in the “power supply chain” I’d certainly posit that it’s the fuseholder. And this type has been used in audio equipment for 50 years. And I guess I’ve answered my initial question!
To end the story, I went to a hamfest this weekend and looked in a couple of the vendor’s fuse/holder bins. Notices what I will call the NEXT larger fuse/holder size which look similar but maybe 1-1/2 times LARGER than the 3AG type – mount in around a 1” hole and secured to a panel by tabs on each front of the holder that mount to the panel via two screws. Holders are appropriately more “meaty”. Could have picked up a bunch of holders for $1 each but didn’t. Will keep them in mind and certainly use this style on any amp I build in the future. Unfortunately there is no room for them in the poor amp that started this whole thing.
ps DO HAVE TO ADD that because of my advancing age I forgot that most equipment built in the last 5 -10 years input mains power via an IEC power connector; some of which have integral fuseholders. The ones that I have examined hold the fuses with two "clips" that appear to make "decent" surface contact with the cups on each side of the fuse. Have no idea what's going on inside the rest of the assembly.
Spent a bit of time over the last week “researching” fuseholders. To be clear, as I’m working on a CERTAIN amplifier and am talking mainly about its fuseholders that “house” the 3AG size (1/4” x 1-1/4”) fuses common in most of the audio US equipment made in the last 50? years. Also referring to what seems to be universally called “panel mount”- ie they mount in a single “D” hole, around 1/2” diameter with a flat on one side so it can’t turn when mounted in the hole.
I started by looking in my fuse holder “junk box” and compared the maybe 4 different styles I had there. These holders, made predominately by Littlefuse / Bussman / et al (in the US) seemed to be the style that has a cap which “holds” one end of the fuse, and affixes to the body by a “bayonet-style” (quarter turn) “lock”. Turns out that the cap of the fuseholder on the amp I’m experimenting with does not have quarter-turn lock but instead screws into holder – don’t know the manufacturer or type (it’s 25 years old).
The back of the “typical” holder has a spring which pushes a rear contact up against the back of the fuse, which then pushes the fuse up against another contact inside the cap. So in effect when the cap is in place, the fuse is “spring loaded” against a front and rear contact. The rear contact seems to “universally” exit the rear of the holder and become the attachment point for a wire connection via either solder or crimp-on connector. The front contact, being in the removable cap, makes “friction contact” with a ring around the holder base which has integral tab or attachment point for the other wire connection to the outside world.
Now all fuses, have a metal “cup” on each end which, implies quite a bit of surface area that a holder COULD contact. However, some of the holders only seem to make minimal contact against (a portion of) the top/bottom of the fuse cup; and remember that this contact is held/made via a spring. Some of what I will call the “better” holders actually have a separate metal “sleeve” that encircle the fuse cups, which in my book add “contact area” – certainly a good thing in my estimation. The other thing that I noticed is that the front “outside world” connection tab on some fuseholders is thinner ( read “puny” and flexible) in contrast to others.
So should I give a **** about any of this? Well I do. This holder is on an amp that supposedly can put out up to 600 wpc into 4 ohms. “Stock” power cable on the unit 14AWG. The power switch has good “wiping action” contacts (I checked). Under normal operation, current consumption can vary all over the place. In this situation, if there is a “weak link” in the “power supply chain” I’d certainly posit that it’s the fuseholder. And this type has been used in audio equipment for 50 years. And I guess I’ve answered my initial question!
To end the story, I went to a hamfest this weekend and looked in a couple of the vendor’s fuse/holder bins. Notices what I will call the NEXT larger fuse/holder size which look similar but maybe 1-1/2 times LARGER than the 3AG type – mount in around a 1” hole and secured to a panel by tabs on each front of the holder that mount to the panel via two screws. Holders are appropriately more “meaty”. Could have picked up a bunch of holders for $1 each but didn’t. Will keep them in mind and certainly use this style on any amp I build in the future. Unfortunately there is no room for them in the poor amp that started this whole thing.
ps DO HAVE TO ADD that because of my advancing age I forgot that most equipment built in the last 5 -10 years input mains power via an IEC power connector; some of which have integral fuseholders. The ones that I have examined hold the fuses with two "clips" that appear to make "decent" surface contact with the cups on each side of the fuse. Have no idea what's going on inside the rest of the assembly.
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If you have fooled yourself, knock your self out on the myriad of snake oil audiophool tweeks. You won't believe the science any way.
The maximum AC power line source resistance (Not the same as just the loss resistance) to a typical single unit house main panel is .06 ohms all the way from the power plant as per the National Electrical Code. (US)
The wiring resistance from the panel to the outlet may vary to as high as .06 ohms but is typically .025 ohms.
The resistance of the AC outlet is .01 ohms or less for even an inexpensive spring clamp wire retaining type.
A bad power cord has .04 ohms of resistance. There are many better and a few worse.
A 5 amp 3AG fuse will have a typical cold resistance of .023 ohms. However of all the resistances in the power line circuit it is the only one that has any significant variation with current and indeed may actually double in value during use.
A 2.5 Amp 3AG time delay fuse which would be reasonable for a 600 watt audio amplifier has around .081 ohms of resistance
A .25 amp 3AG fuse may actually have more than 2 ohms of resistance cold and also double to 4 ohms in use.
It seems some fuses do contribute most of the AC line resistance and worse it varies with the current draw unlike the line resistance.
Now in a well designed circuit this should not be an issue, but we are discussing AUDIO equipment!
Simon, you forgot the resistance (and inductance) in the wiring from the powerplant to your wall-socket
.... minor detail, I know
No that is the first number. .06 Ohms power plant to fuse box! Do you know why it is so low?
Simon, you forgot the resistance (and inductance) in the wiring from the powerplant to your wall-socket
.... minor detail, I know
And the transformer.
Those fuse resistance values are vey low when compared to TX primary resistance.
How much difference does fuse resistance modulation actually make, and how does it affect in your exp/opinion ?.
Dan.
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