Fuses do affect sound, the question is how much

[Wombat]

I don't know why people are fighting in the world.

This thread is about fuses, mate.

 

[blackmetalboon]

Discussions about these fuses are currently (pun intended) doing the rounds on UK forums, I’d not really taken much interest until I saw images of them, specifically fuses designed to go in our plugs.


Due to our wiring regulations in the UK we have a fuse in our plugs (many other countries also use either our wiring regulations or our plugs and sockets), this is used to protect the cable supplying the equipment. There are specific requirements to this fuse set out by British Standards (BS), BS 1362 is the relevant standard for plug top fuses. The majority of these audiophile aftermarket fuses do not have any information or markings in them to indicate wether or not they conform the BS 1362. Some have the CE mark on their packaging but national standards, such as BS, trump CE markings. In fact it could be an offence under the Trade Descriptions Act to use such a marking in them.


Without any information on these we have no idea how they react under inrush current, how much current is required before they blow or their maximum power dissipation. Digging around other forums it appears people have contacted the relevant manufacturers and retailers but no definitive information has been forthcoming.


Unfortunately BS 1362 costs around £170, so I don’t have access to it, but I’d be interested to see how far these fuses deviate from it.

 

[Wombat]

Discussions about these fuses are currently (pun intended) doing the rounds on UK forums, I’d not really taken much interest until I saw images of them, specifically fuses designed to go in our plugs.


Due to our wiring regulations in the UK we have a fuse in our plugs (many other countries also use either our wiring regulations or our plugs and sockets), this is used to protect the cable supplying the equipment. There are specific requirements to this fuse set out by British Standards (BS), BS 1362 is the relevant standard for plug top fuses. The majority of these audiophile aftermarket fuses do not have any information or markings in them to indicate wether or not they conform the BS 1362. Some have the CE mark on their packaging but national standards, such as BS, trump CE markings. In fact it could be an offence under the Trade Descriptions Act to use such a marking in them.


Without any information on these we have no idea how they react under inrush current, how much current is required before they blow or their maximum power dissipation. Digging around other forums it appears people have contacted the relevant manufacturers and retailers but no definitive information has been forthcoming.


Unfortunately BS 1362 costs around £170, so I don’t have access to it, but I’d be interested to see how far these fuses deviate from it.

Some info:

http://www.bs1363.org.uk/DTI_warning_on_Counterfeit_Fuses_web.pdf

https://www.pat-testing-training.net/articles/fake-fuses.php

 

[blackmetalboon]

Some info:

http://www.bs1363.org.uk/DTI_warning_on_Counterfeit_Fuses_web.pdf

https://www.pat-testing-training.net/articles/fake-fuses.php

This highlights some of the potential problems with these audiophile fuses. How do we know that they’re not sourced from the same factories that make counterfeit fuses?

We have audiophiles turning a blind eye to this issue. Their only defence is that, subjectively, it makes their system sound better while choosing to ignore (however minute) the possible safety implications.
It’s potentially like removing the seatbelts from you car and using a piece of string instead as it will make your car go faster because it’s lighter.

 

[blackmetalboon]

Here is a link to some measurements taken of audiophile fuses.

http://www.hifi-tuning.com/pdf/wlfr.eng.pdf

 

[Sal1950]

Here is a link to some measurements taken of audiophile fuses.

http://www.hifi-tuning.com/pdf/wlfr.eng.pdf

Amazing results, the manufacturer that did the testing, his fuses measured the best.

 

[Superdad]

Amazing results, the manufacturer that did the testing, his fuses measured the best.

And yet you complain when manufacturers don’t publish any measurements. Bit of a double-standard, eh?

 

[Speedskater]

This highlights some of the potential problems with these audiophile fuses. How do we know that they’re not sourced from the same factories that make counterfeit fuses?

And/or how do we know that they will follow the correct time & current response curve that well chosen fuses do?

 

[Dimitri]

Amazing results, the manufacturer that did the testing, his fuses measured the best.

When you put in the effort make damn sure it's worth it !

 

[Wombat]

Here is a link to some measurements taken of audiophile fuses.

http://www.hifi-tuning.com/pdf/wlfr.eng.pdf

Throw up a whole lot of measurements, fail to validly explain or demonstrate any audible effects, and then claim they are audible but less so with your product(no valid audibility test method put forward).


Pseudoscience: http://whatis.techtarget.com/definition/pseudoscience

 

[Sal1950]

And yet you complain when manufacturers don’t publish any measurements. Bit of a double-standard, eh?

My my, look who's crawled out of the woodwork. You selling fuses now too?

No double standard, not criticizing the work being published,. Just my usual skeptical, suspicious self.
But yes, the good news is the measurements are there and could be verified if anyone thought it worth the effort.

 

[RayDunzl]

Here's a couple of common fuse data sheets...

http://www1.cooperbussmann.com/pdf/b040436b-cbc7-495d-95a6-99fe85202786.pdf

http://www.littelfuse.com/~/media/e...fuses/littelfuse_fuse_219xa_datasheet.pdf.pdf

 

[trl]

Amazing results, the manufacturer that did the testing, his fuses measured the best.

"The high end fuses all give better results in conductivity"

One thing's for sure and it's also clear from manufacturer's data-sheet: a fuse has an internal resistance higher than zero Ohms, same applies to fuse holder. However, I have doubts that few mV out of 230V can make a difference inside a 15VA power consuming DAC or headphone-amplifier, especially with internal regulated PSUs that are able to operate perfectly from down to 100-150V (depending of type and manufacturer). Also, if a simple 2-stage EMI/RFI filter is used inside the box, then this should get rid of most possible AC noise already, then the internal PSU's regulators should lower the AC ripple with 60-90 dB, depending on the type of regulator used.

If speaking about high contact resistance between the fuse and the holder (especially for few kW/channel power amplifiers for outside use) now this can be an issues when handling high power speakers, because bass could decrease in quality and power if 10-20V get lost out of 230V (if non-regulated linear PSU is used; if SMPS is used, then this might not apply at all...depends). Same applies to cheap thin power cables, but only for high power delivery amps, not for low power SOHO devices like DACs and headamps.

P.S.: If someone can actually prove that at the output plug of an amplifier the SNR, THD or dynamic is indeed getting modified when swapping different fuses of the same value (mA & VAC), then it would be interesting to have a look at the measurements.

P.P.S.: I would honestly care more about better quality XLR/RCA/jack plugs to prevent oxidation then fuses that are already covered inside an almost sealed box.

 

[audio_tony]

Fuses get very nonlinear as they approach their current limits. Even before that electromigration raises their impedance, more a problem in a DC line (e.g. power supply) than the AC input fuse. In a power line this is usually a don't-care; in a speaker line the effects of a fuse are generally to raise the output impedance (meaning less control of the speaker and all that implies) and potentially to raise the distortion. As has been noted, until it blows, the added distortion and frequency modulation is usually slight but measurable. Audible? I'll pass on that one...

If an amplifier is being driven that hard, that the DC fuses are showing signs of strain, then I'd suggest that fuse distortion is the least of your worries as there will be a myriad of other distortions to consider.

Rather upgrade to a more powerful amplifier, that doesn't need to be pushed to it's limits to be loud enough.

 

[DonH56]

Don't think anything in my post would disagree with that... The argument was used to get rid of speaker fuses, same (questionable) reasoning applies.

 

[trl]

Given the graph from https://m.littelfuse.com/~/media/fi...ference-documents/elec_fuse_temp_derating.pdf for the slow blow fuses, seems that power rating varies with at most 20% in temp. increases from 25C to >100C. I assume that if internal power rating varies with about 20%, then same applies for the internal resistance.

I really think that the few mOhms added to internal resistance of a slow-blow fuse with increase of power consumption and heat should be enough to change the title of this thread.

 

[DonH56]

Fuses unquestionably affect the sound. When a fuse blows, the sound goes away.

 

[trl]

Good one Don!

I guess worst case scenario would be the addition of 0.1 Ohms to the output impedance to the amplifier, so not quite a game changer.

Maybe I'll have some time this weekend to setup my DIY "lab" supply to 20V and test how voltage that drops on the fuse varies, based on increasing current from 0.1A to let's say 1A. I'll put the fuse to short-circuit PSU'soutput...or maybe I'll add a resistor, I'll see.

 

[DonH56]

Fuses can contribute significantly to the output impedance of an amplifier and thus could change the frequency response. Depends on the amp and speaker. I still suspect cost is one of the biggest drivers in getting rid of speaker fuses.

I measured a bunch of fuses ages ago as I ramped them to failure. That data is long gone, along with most of the measurements made back then (late 1970's through mid-1980's -- I have looked for the boxes of papers unsuccessfully several times now). I can usually remember results but in this case I do not. IIRC there was a pretty significant variation, albeit mostly linear until near destruction. Metals tend to have very high tempco's but it is usually neglected as the resistance is low w.r.t. other resistances in the circuit. Not the case in an ADC or DAC reference ladder; dealing with the tempco of the gold traces on a 16-bit DAC I designed back in the dark ages was a PITA.

100 W into 4 ohms is about 5 Arms so some modulation of resistance through a fuse will happen. Audible? Not something I feel like stepping into... I did get to replace a number of damaged drivers in speakers when owners decided to replace fuses with pieces of wire. The effects of the fuses might of been audible at the levels they were driving the speakers, but I suspect power compression was a bigger player. Paid more to me to have them blow a driver than a fuse but I would routinely tell them they were stupid (OK, not "stupid", I advised them against bypassing fuses -- can't tell the customer he's wrong ).

 

[amirm]

Given the graph from https://m.littelfuse.com/~/media/fi...ference-documents/elec_fuse_temp_derating.pdf for the slow blow fuses, seems that power rating varies with at most 20% in temp. increases from 25C to >100C.

Slo-blo fuses are very uncommon in today's electronics. They would get a more use in tube products, things with motors and such.