I take it you didn't read all of my posts. The fuse is the only variable resistance in the power source. All the nonsense about how can this be with the power grid is just uniformed.
Now if you have a 600 watt amplifier the maximum draw should actually be around 24 amps peak! (From measurements as the capacitor bank only charges for part of the power cycle.).
So the issue becomes does the .25 ohm typical peak modulation change affect the 5 ohms equivalent of the amplifier draw.
My conclusion is that it should not in a properly designed circuit. That is partly from the transformer normally runs a bit into saturation to improve the regulation. In addition even a very good transformer will sag by at least 5% under full load. However as we are talking about audio amplifiers many of them not only have poorly designed power supplies but there are also issues in how the stages are designed to reject not just power supply droop but also the noise currents and voltages during those peaks.
So while a fuse in a loudspeaker line has long ago disappeared the power supply ones are mandatory. Thus recognizing the issues involved is the first step in avoiding problems. That was the original issue essentially is there a low loss fuse holder?
The question has been addressed by serious folks. It is the uniformed commentators who dismiss a legitimate question.
As to power cords making a difference, they certainly can. Besides using one that really can't handle the current the real issue is do they add line noise filtering.
A 600 watt amplifier drawing full power puts a lot of noise back onto the AC mains. This often affects other equipment. So there are actually line cords designed to filter noise without the use of inductors that add line resistance.
Now for those who don't get it Scott really does use fuses.
So please don't get confused by the trolls who want to spout off without ever having made any measurements or even read the technical texts. That is why I ask some trivial questions that they really don't have a clue about.
Okay, now I've made myself feel a bit guilty, so a less flippant reply:
-- Jim
A lot of this seems to keep coming back to whether the equipment is competently designed or not, as you have mentioned at least once above. The obvious solution appears to be, why not just buy or build gear that isn't so petulant to begin with? God knows for the prices they charge for some of these AC cords for example, you could easily find a CD player/ server/ whatever that simply isn't bothered by the all this noise your 600W power amp is inflicting on your power lines (assuming, of course), with plenty of money left over to buy more music.
I got that, thanks.
-- Jim
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Look at Panos tests with signals through Mud etc. Lets get some reality and science back in Audio
He doesn't like it when people see the trick. I figured this one was too obvious for you to bother.
Hint: add Ed's numbers together and use Ohm's Law. Oops, looks like something's missing...
How can a cable filter, a filter filters not a cable... this was the issue Russ Andrews got a wrist slap for claiming a cable filtered EMC...
24A at 120V?
I was being ironic. Fuses just ain't an issue for me. I don't see what all the fuss is about
No. It was only after I posted that I thought that maybe it was a DIY amp; no commercial amp could include such a foolish feature.50AE said:
Given that fuses are resistors with short thermal time constants it is possible that a badly placed fuse could affect sound. Therefore part of good design is to put the fuse in the right place so it doesn't affect sound. If a mains fuse affects sound then there is something wrong with the PSU design.Max Headroom said:
I was being ironic. Fuses just ain't an issue for me. I don't see what all the fuss is about
i realised after I'd posted....
The transformer is only "connected" to the smoothing caps while the diodes are conducting. i.e. for about 10% to 20% of the time.
If a fuse on the other side of the transformer affects the sound while it is effectively connected for about 15% of the time, it must be an enormous impedance to so severely affect the source impedance seen by the transformer primary.
I suspect one would be able to measure the effect of the added fuse impedance, but I won't believe it would affect the sound.
If a fuse on the other side of the transformer affects the sound while it is effectively connected for about 15% of the time, it must be an enormous impedance to so severely affect the source impedance seen by the transformer primary.
I suspect one would be able to measure the effect of the added fuse impedance, but I won't believe it would affect the sound.
I expect that a time delay fuse is used. A 600 watt amplifier even in commercial service will draw an average of 120 watts.
When I do a stadium with 5000 watt amplifiers they will sometimes trip a 20 amp circuit breaker but never a 30 amp one.
Fast blow fuses can be used if the design has consistent turn on characteristics. For example a soft start circuit.
Marce,
If you peruse the patents you will find folks who build power cords with the mains leads twisted as a pair and the safety ground lead not included. Some even add a braided shield. But my favorite has a less conductive coating on the wires so that skin effect of high frequencies is supposed to cause more losses of high frequency noise. Then there are the ones that use ferrite material surrounding the conductors either plated or in the first layer of insulation. I suspect there may even be designs that wrap the copper vonductorvaround magnetic one. You actually can build a low pass filter without discrete inductors.
But a designer understanding the issues will not only try to keep noise out of their gear but also try to be a good neighbor and not pollute the power lines.
And a bit more about capacitor charging. The power supply capacitors begin charging as soon as the input voltage goes above the stored voltage. This is the high current draw time. As the charging voltage peaks the charging current decreases so the transformer unloads a bit and floats up a bit. This extends the charging time. The diodes thus allow noise in for a bit more time.
SY if there is a bit of arithmetic that confuses you just ask. You're hinting there is an issue is not just snide, it demeans the level of technical conversation.
Show me some patents, I'll bet there all audio based.... I do wonder why in the normal world of electronics I have never come across these sort of cables, shielded obviously but none that claim filter, always use filters for filtering...
Some links would be appreciated though, you never know
Some links would be appreciated though, you never know
Show me some patents, I'll bet there all audio based.... I do wonder why in the normal world of electronics I have never come across these sort of cables, shielded obviously but none that claim filter, always use filters for filtering...
Some links would be appreciated though, you never know
Well if you worked on gear as badly designed as some of the stuff you might need almost magical cables. In your world there are these nice premade filters that work better than just the power cord filter. There also are EMI standards you have to follow. Most consumer gear is exempt and audiophile level never paid attention anyway.
If I get the chance I'll cite a few of them. But yes they are all audiophile. Who da thunk it. Oh you did.
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Bill Whitlock has one such paper (the patent app. is ugly). But it has little to do with filtering.Show me some patents, I'll bet there all audio based.... I do wonder why in the normal world of electronics I have never come across these sort of cables, shielded obviously but none that claim filter, always use filters for filtering...
Some links would be appreciated though, you never know
"Ground Loops: The Rest of the Story"
Bill Whitlock and Jamie Fox
This paper was presented at the AES 129th Convention, 4-7 November 2010, San Francisco, CA, USA
ABSTRACT
The mechanisms that enable so-called ground loops to cause well-known hum, buzz, and other audio system
noise problems are well known. But what causes power-line related currents to flow in signal cables in the first
place? This paper explains how magnetic induction in ordinary premises AC wiring creates the small voltage
differences normally found among system ground connections, even if “isolated” or “technical” grounding is
used. The theoretical basis is explored, experimental data shown, and an actual case history related. Little
has been written about this “elephant in the room” topic in engineering literature and apparently none in the
context of audio or video systems. It is shown that simply twisting L-N pairs in the premises wiring can
profoundly reduce system noise problems.
http://xa.yimg.com/kq/groups/20963848/268252969/name/Whitlock-Fox+-+Ground+Loops+.pdf
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