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Fuses do affect sound, the question is how much

tomelex

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#1
OK, so about forty years ago I watched a fuse pulsate to the bass beats in an amplifier. It was a fuse in line with the speaker, and for speaker protection.

Fuses react to current flow and they heat up when it happens. Now, I don't think I heard the affects of this fuse whose impedance was increasing on each surge of bass current to the speaker, but it is a varying resistance and so it will also affect lower energy but higher frequency pulses going through it (that is a higher impedance (impedance resists current flow or restricts it)would therefore encounter more impedance than if the fuse impedance was not changing. What I mean is lower energy signals will be impeded more by this higher impedance state of the fuse on those bass notes that "pulsate" the fuse.

So, yes, anything in line with the signal can affect the signal or sound. This pulsation is also not linear, so that also can affect the sound.

That's pretty much a short summings up on fuses in the audio path.

I do not say that any so called audiophile fuses are any better, I will say that if the fuse is not used directly in the audio circuit path, (ie it is used in the incoming mains ac power) it is highly unlikely to have any audible improvement for even the most golden of golden ears and I would place some money on those bets any day of the week.
 

iridium

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#2
Excellent information!
Thank you.
iridium.
 

amirm

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#3
I don't know that I have seen any fuses in today's electronics that is in audio path. Back in 1970s some were in the amplifier circuits but these days it is all electronic control and relays. Fuses if they exist are in power supplies and such.

Yes, I remember seeing fuses pulsate too. I don't think that is a sign of good design :). A fuse would have to be pretty close to blowing up to heat up that much. If they do vibrate I agree about their dynamic behavior having an effect.
 

Thomas savage

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#4
i have had mixed results with audiophile fuse in my gear (slow blow) in the power domain not signal, they seem to change the sound but not always in a good way. using furutech at the moment, they are the best i have found. dont do anything weird just seem to make things better ( or at least not worse) of course many would say such changing sound is impossible from a fuse change and that's fine by me. you can laugh at me while i laugh at you, everyone is happy and laughing:D

you can even ridicule me, this way you're increasing the value of my investment into the fuse by getting some indirect joy out of my purchase too... just make sure your laughing while doing it. ;)
 

amirm

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#5
I like to collect a list of such topics to put to test one day. Would be interesting to measure what the fuse does when current pulsates through it. Thomas, will you send me some of your expensive fuses to test with? :)
 

Thomas savage

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#6
I like to collect a list of such topics to put to test one day. Would be interesting to measure what the fuse does when current pulsates through it. Thomas, will you send me some of your expensive fuses to test with? :)
they are not expensive (£60), some are though. i got negative results with most i tried and went back to stock type (£5 each) that russ andrews sell(they are cryo treated though:p) but revisited the subject and was happy with the (mild) benefits of the furutech.

my advice is dont bother unless you are a nutjob like me, i tried loads and spent easy £1000 with many disappointments and some blow outs. i opened some up too, got to look inside these things:eek:

oh and apart from living in a house that's a assassins dream target environment you're doing better than me so buy your own..:p:D
 

tomelex

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#7
i have had mixed results with audiophile fuse in my gear (slow blow) in the power domain not signal, they seem to change the sound but not always in a good way. using furutech at the moment, they are the best i have found. dont do anything weird just seem to make things better. of course many would say such changing sound is impossible from a fuse change and that's fine by me. you can laugh at me while i laugh at you, everyone is happy and laughing:D

you can even ridicule me, this way you're increasing the value of my investment into the fuse by getting some indirect joy out of my purchase too... just make sure your laughing while doing it. ;)

I am going to keep an eye on you :)
 

Speedskater

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#8
Fuses are typically used in three different circuits in an audio component:
1] AC power supply.
2] DC power supply.
3] Audio output of a power amplifier.
The audiophiles that hear these differences never mention which circuit the fuse is in.

Moving on, Bob Cordell is his great book "Designing Audio Power Amplifies" did measure fuse THD in an audio output stage.
It's section '13.11 Fuse, Relay and Connector Distortion' page 268.
Conclusion:
"At 20 Hz, amplifier distortion due to the fuse is calculated to be 0.0033 %."
 

Thomas savage

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#9
Fuses are typically used in three different circuits in an audio component:
1] AC power supply.
2] DC power supply.
3] Audio output of a power amplifier.
The audiophiles that hear these differences never mention which circuit the fuse is in.

Moving on, Bob Cordell is his great book "Designing Audio Power Amplifies" did measure fuse THD in an audio output stage.
It's section '13.11 Fuse, Relay and Connector Distortion' page 268.
Conclusion:
"At 20 Hz, amplifier distortion due to the fuse is calculated to be 0.0033 %."
i did
 

DonH56

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#10
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...
 

Bruce B

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#11
There are quite a few speakers with fuses in the signal path going to the x-over. Think Magnepan......
 

RayDunzl

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#12
Taking a 120v 100W light bulb as a rough example for argument:

When cold, it's a short.

When white hot, and assumedly near its fusing point, 144 Ohms.

(you guys argue)

(I'll read up on fuses, since this would not be a proper fuse)
 
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DonH56

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#13
A common but misleading argument since the metals in filaments are different, designed to radiate, and operated such that they do radiate (we hope). Fuses are generally low impedance until near their melting (breaking) point and I have never seen one radiate except a brief flash as it blows.

My opinion is that speaker fuses fell out of favor more in concession to audiophile marketing and manufacturer cost (why add something people fear will hurt the sound?) than due to any audible issues. Amplifier output protection has also improved over the years, and other components are less likely to emit damaging "thumps" since low-level muting circuits have also improved.

YMMV - Don
 

amirm

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#14
Taking a 120v 100W light bulb as a rough example for argument:

When cold, it's a short.

When white hot, and assumedly near its fusing point, 144 Ohms.

(you guys argue)

(I'll read up on fuses, since this would not be a proper fuse)
A light-bulb actually makes a great reusable fuse! When repairing high-power amplifiers that may have shorted out, you put a bulb in series with them. If the bulb goes full power when you turn on the amp, you know you have a nasty short which would have done more damage if you had not used the bulb. Every repair shop has one of these. It is a life saver and great diagnostic tool. You can even set the bias in an amplifier by watching how much the bulb lights up as it acts like a visual watt meter.
 

RayDunzl

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#15
A common but misleading argument since the metals in filaments are different, designed to radiate, and operated such that they do radiate (we hope). Fuses are generally low impedance until near their melting (breaking) point and I have never seen one radiate except a brief flash as it blows.
I understand.



"Variations in temperature are quite colorful, and they’re also
quite useful in rooting out problems such as the equipment fuse
problems shown here"
 

DonH56

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#16
Yes, we have IR sensor-based ("heat reading") imagers and meters at work, but they can read temperatures (radiation) that are at wavelengths well below what we can perceive visually. Or at least what I can. YMMV. An ammeter, or better yet good current-sensor and DSO, does a good job at assessing the current flow through a fused line.

I have discovered trying to change another's religion is an impractical and frustrating task. Since I am in no way a fuse expert I shall bow out of this one. The measurements I took are just a memory, no written proof (at least that I could find), and I feel no strong need to evangelize about the pros or cons of audiophile fuses.
 

RayDunzl

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#18
I can make measurements :). Let's talk about the scenario and I will then do the work.
I have an Acurus A250, a somewhat utilitarian stereo amp. Rating 250/350 8/4ohm.

My speakers (Martin Logan reQuest) are rated 4 Ohm and measure 4 Ohm (DC), with the usual electrostatic dip up top. 48x15 panel, 12" sealed woofer, 180Hz cross.

upload_2018-3-29_14-52-29.png


Big transformer, big caps, fused input (which remains) and 6A fast blow on each driver board, I assume near the input.

Since it had a fused input, at some point about 1999 I tried bypassing the board fuses, and the result 'sounded' good. The subjective impression was a little more forceful presentation. A little more stable. I liked it, so they stayed.

No measurements other than VOM volts and simple 'scope waveforms across the fuse holders were possible. I don't remember the numbers but they were substantial enough to encourage me to bypass them.

It was retired from front-line duty 4 years ago for a pair of Krell FPB 350mcx, which, subjectively, are much more better. My ear says the harmonics (which give tones texture) are much closer to where they should be. the Acurus is in a side room and plays Tibetan chants to my dead relatives from time to time.

The other mod I applied to it was to bypass the big caps with some small non-electrolytics liberated from Telecom Duty at work. And ferrite clamps, reducing RF hash on cable ends, whether actually beneficial or not. Lots of them, still have a big bag.

The Krells... Horribly complicated ( regulated power, stepped bias, sort of Class A) and not green at all (100W idle each) but real nice sounding. They have breakers as power switches and unknown protections beyond that. Power rating 350/700/1400 8/4/2 Ohms. No mods anticipated here.




 
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amirm

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#19
There sure is stark comparison between the two amps. There sure are a lot of fuses in your smaller amp. I suspect a couple are for power supply. But others may be output protection. Hard to tell from the picture.
 

RayDunzl

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#20
There sure is stark comparison between the two amps. There sure are a lot of fuses in your smaller amp. I suspect a couple are for power supply. But others may be output protection. Hard to tell from the picture.
I think they were board supply fuses, +/- at the board input, total 4, and a fuse at the AC inlet.

Look at the right hand side, you'll see the +/- from the caps hit the board very close to each fuse.

The speaker out is short red/black right at the end of the board.

---

Document:

A250 Internal—rail fuses 6A fast blow 2/channel. Can be 5mm X 20mm or ¼ X 1 1/4
 
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