Upgrading AC cord and fuse??????

[JoeDJ]

I have been reading how some think that uprading an replacing a perfectly good AC cord for an amp can improve the sound. Considering what AC has to go through before it even gets to a wall outlet, how can a few feet of AC cord affect anything when one considers electicity does not care what a cord looks like or how much you (over) paid for it.

These same people claim that replacing a fuse can noticeably improve sound.


To me all this is just plain ol'' BS!

Is there any truth at all to this?

[DF96]

The mains cable can change (by a small amount) the source impedance seen by the PSU. This can (slightly) change the shape of the charging pulses in a capacitor input PSU. Poor amp design can couple these to the audio circuitry. General rule: if changing the mains cable changes the sound then there is probably a weakness in the design of your amp, however much you paid for it. Similarly for fuses.

[JoeDJ]

Yeah but, my thinking is if the mains is at least as good qualty as the house wiring leading up to the wall outlet, how can a "better" mains to the amp possibly help?

[DF96]

A 'better' one might make no difference, but a 'worse' one (e.g. highish resistance and/or high inductance) might give slightly smoother charging pulses. Don't assume that expensive cables are necessarily 'better'. If you read the sales blurb you can see that some of the makers simply don't understand electricity, or at least hope their customers don't.

Another issue is ground lead impedance. It could be that a thinner, higher impedance ground lead could force more of the signal return currents (at low frequencies) to travel via the interconnects' screens rather than the mains ground wires. A 'worse' mains cables might reduce ground loops, by raising the loop impedance.

[jitter]

Humans are very suscpetible to suggestion, especially when it concerns something they don't really know anything about but which might have a big impact. If enough people say something is true, then that something becomes truth. Just think about how many times history has proved us wrong and continues to do so.

Those that have knowledge about that something will not be fooled so easily, though.
Same thing here with HiFi, there are audiofiles and audiofools.

Personally I think that changing AC cords and fuses will not make any difference when it comes to equipment that has been designed to meet EMC criteria. You're not going to change the properties of a high level mains signal more than a negligible amount with just a short length of conductor.
When it does make a difference, there's probably something fundamentally wrong with that equipment, like DF96 mentioned, or you're fooled into believing it does. If there is a preceptible difference, it's time for some double blind testing. If the difference persists, it's time to track down the real culprit.

I run my audio equipment on their standard AC cords but behind a mains filter. I can't hear the difference with or without filter, but I keep it there anyway for peace of mind.

[JoeDJ]

I guess when all is said and done, a little peace of mind can be good.... as long as it does not cost too much.

I suppose a high quality fuse can help a depending on the circuit and the fuses involved.

However, I still have a problem with the mains.
Installing a better amp mains than the wiring in the walls can help?
That's like saying installing one strong link in a a chain where all the other links are weaker and expecting the whole chain to be stronger. The most common house wiring gauge in the US is 12-14 for most room 110 outlets. So why install a 7 gauge amp mains?

[AndrewT]

A cable has resistance and capacitance and inductance.

Changing the geometry of the cable changes the relative proportions and the absolute values of these impedances.

Once you change those impedances you have changed the filtering effects.

That is what DF & Jit are referring to.

A good amplifier (or other equipment) should remain unaffected by changes in the interference coming in through the mains. A poor bit of gear could easily be heard to respond to changes in mains borne interference.

A change of cable parameters can affect the interference that escapes from the mains to the gear.

That's where removing the fault in the gear comes into the equation. Sort the problem. Don't reduce or hide the problem by fiddling with cables.

[simon7000]

The source impedance from your wall is often between .1 to .3 ohms. Why don't you measure the resistance of your cord and fuse?

[DF96]

As I said, a 'better' mains cable might make sound worse. A 'worse' one might improve things by adding resistance. A 'worse' mains cable might be more expensive than a 'better' mains cable, if it is accompanied by a more imaginative story.

[SoNic_real_one]

The worse offenders on the AC power supply chain are:
1. Contact resistance of the plug/receptacle. If the receptacle in the wall has weak springs, oxidated lamels (running a space heater in it will do that), then the instantaneous voltage drop on that connection can be important. In Eu some countries have different outlets - the 16A one with grounding (Schuko or CEE 7/17 style) has a bigger diameter prongs (4.8 mm) than the 2.5A CEE 7/16 Europlug ones (4mm). Using the wrong cable in the wrong socket will lead to imperfect contact.
To make things worse, the Russian plugs have the same spacing as EU plugs, but theyr prongs are 4.5mm in diameter. Sockets conforming with that standard are found in a lot of former "east-european block" countries.
US plugs are better designed because they need to handle higher currents by default and they are polarized (hot/neutral). An universal 15/20A receptacle is designed "host" a 15A or a 20A plug. Obviously that receptacle is the best upgrade for a 15A household device, but only if the wiring in the wall is also upgraded to 20A (#10AWG), otherwise is not "legal" per NEC.
2. Diameter of the conductors inside the cord. In order to make the cord flexible, some manufacturers choose really thin wires (for example in EU adequate only for 2.5A, or in US #18AWG). Those will add to the voltage drop and they are definitelly smaller than wiring in the wall.
3. Fuse. The fuse itself has to have a certain voltage drop over it in order to develop the temperature faster than the protected circuit. So yes, eliminating the fuse can improve the voltage drop, on expense of increasing the risk of fire. It is strongly NOT my advice. There are faster fuses (filled with sand usually) that have a lower voltage drop compared with the regular ones, but I doubt that is a very big variance.
4. I almost forgot. The automatic circuit breaker in the electrical panel has a sizable resistance, some inductance and a contact. All generate voltage drops.

Because the power supply of most devices is regulated, all this does not have any sizable effect on audition. The power amplifiers don't have regulated power supplies, but they usually have good PSRR by design. In some, PSRR is not so good, and the cable might make a slight difference at maximum volume.

But in most cases, it is just "whishfull thinking" in effect. Self-suggestion.