Audiophile Fuses

Sablon Audio

Industry Expert, VIP Donor
May 22, 2015
947
556
448
Whilst it’s massively irritating to have an expensive SR Blue blow prematurely, one can take some consolation that they do actually respond and can correspondingly also feel comfortable taking the next rating up. Highstream alluded to this earlier and I generally use an SR Blue with a +33 - 50% greater amp rating.

People also need to take care with the rating used in 230 v 120 volt applications - Ohm’s law means that the amp rating changes proportionately.
 

dan31

Well-Known Member
Jul 22, 2010
616
125
453
SF Bay
A little insight from Ayre Acoustics founder.

“This is another reason why I've not experimented with fancy fuses -- the penalty factor for any sort of problem is pretty high...

Real fuse companies rate their fuses by a quantity called "I^2t", pronounced "eye squared tee". This is an amount of energy that is the current (in amperes) squared times time (in seconds). This puts a quantitative value onto a subjective label such a "fast blow" or "slow blow". So for example, we can look at the Littelfuse website and see that their Series 218, 5x20 mm, 1 amp, slow blow has an I^2t value of 6.73 A^2sec. This is what we use in our products.

http://www.littelfuse.com/~/media/Electronics/Datasheets/Fuses/Littelfuse_Fuse_218_Datasheet.pdf

Now if we go to Digikey, who sells a large number of brands and put in the same specifications -- Glass Cartridge, 5x20 mm, 1 amp, slow-blow, 250 VAC, we can find I^2t values ranging from 2.4 A^2sec to 28 A^2sec, a variation of greater than ten to one! So a 1 A slow-blow fuse is not a 1 A slow-blow fuse.

The peak surge energy drawn by any specific piece of equipment will depend on many factors. First of all the largest surge occurs at turn-on. There are two main culprits. The first is the transformer itself. If you put a multimeter across the primary leads, the DC resistance will generally read in the range between a few tenths of an ohm (for a large transformer) and a few ohms (for a small transformer). If this is all there were to the situation, the transformer would be more like a light bulb, glowing red hot until it melted. But we are not sending it DC during actual operation but instead AC. Now the inductance of the transformer comes into play and limits the current. Every transformer has some "leakage inductance". This is inductance in the primary winding that is not coupled to the secondary winding, but instead creates a stray magnetic field around the transformer. This requires energy, and hence some current draw. At turn-on, it takes a fraction of a second to build up this magnetic field, and while it is doing so, it draws more current than normal.

The other culprit are the filter capacitors. These are charged up from zero volts to their full operating voltage. usually within about ten cycles of the 50 or 60 Hz incoming voltage. For the first half cycle, the capacitor is virtually a dead short and the only thing that limits the current are the stray resistances of the internal wiring, the primary and secondary windings of the transformer, the fuse resistance, and the impedance of the rectifiers, et cetera. We have a Tektronix current probe that connects to an oscilloscope and we were measuring the peak current at turn-on for the new VX-5 power amplifier, and even though it idles at about 2 or 2.5 amps, the peak turn-on surge was well above 50 amps!

In this case the only thing to do is use a higher value for the KX-R. You can ask Synergistics what the I^2t value is for their fuses and get one that is at least 7 A^2 sec. I'm sure it won't hurt to go to 10 A^2 sec. However I would be surprised if they have that data. If not, just go to the next larger size. The I^2t values climb very quickly. For example the same Littelfuse in a 1.25 A rating has roughly double the I^2t as the 1 A fuse, and the 1.6 A fuse has roughly double again the I^2t rating. But at $30 a pop, it is pretty expensive experimentation...”

Good luck,
Charlie Hansen
Ayre Acoustics, Inc.
 

ack

VIP/Donor & WBF Founding Member
May 6, 2010
6,342
798
610
Boston, MA
Great stuff, thanks; the pdf link is broken
 

internethandle

New Member
Oct 28, 2019
1
0
1
36
Anyone tried the new SR Orange fuse? I tried a Blue for approx. 12 days before deciding it wasn't for me, but am curious enough after an Audiogon user reported that the Blue to Orange was an even bigger difference than going from Black to Blue in his system. It's only about $10 to $15 more than what the Blues were going for, and VH Audio at least has seemed to have lowered the Blue's price to around $125, subsequently.
 

highstream

Well-Known Member
Nov 16, 2013
347
120
273
I didn't like the Blue either for it's tonal coolness and went to the AM Ultimate Beeswax, which I found having a natural warmth and liquidness. What's caught my attention in that Agon thread is the OP's mention of the Orange is SR having added warmth in the lower midrange. I have a couple of new pieces to change fuses in, but I'm going to wait to see others' comments, and maybe ask a few questions, before deciding whether or not to give it a listen. Saving $65+ a fuse would be nice.
 

sbo6

Well-Known Member
May 19, 2014
1,069
151
285
Round Rock, TX
Whilst it’s massively irritating to have an expensive SR Blue blow prematurely, one can take some consolation that they do actually respond and can correspondingly also feel comfortable taking the next rating up. Highstream alluded to this earlier and I generally use an SR Blue with a +33 - 50% greater amp rating.

People also need to take care with the rating used in 230 v 120 volt applications - Ohm’s law means that the amp rating changes proportionately.

Please help me understand how going outside of the recommended amp rating is acceptable and safe for equipment? I understand tolerances but up to 50%? Seems like a good way to fry your equipment.
 
  • Like
Reactions: christoph

highstream

Well-Known Member
Nov 16, 2013
347
120
273
@sbo6. Did you read Charlie Hansen’s exolanation?
 

sbo6

Well-Known Member
May 19, 2014
1,069
151
285
Round Rock, TX
Just read it, thanks.
 

Sablon Audio

Industry Expert, VIP Donor
May 22, 2015
947
556
448
Please help me understand how going outside of the recommended amp rating is acceptable and safe for equipment? I understand tolerances but up to 50%? Seems like a good way to fry your equipment.

If SR fuses are going pop with regular start up surges but generics don’t, then their actual rating is lower than what is printed on them. Ergo, you are not actually going out of tolerance.

If however you do go outside of tolerance, then the higher rated fuse will blow a few milliseconds later. This advise was actually given to me by a valve amp builder.

Neither of these would however be the cause of your equipment going up in smoke - that would be due to a faulty component or user error.
 

sbo6

Well-Known Member
May 19, 2014
1,069
151
285
Round Rock, TX
If SR fuses are going pop with regular start up surges but generics don’t, then their actual rating is lower than what is printed on them. Ergo, you are not actually going out of tolerance.

If however you do go outside of tolerance, then the higher rated fuse will blow a few milliseconds later. This advise was actually given to me by a valve amp builder.

Neither of these would however be the cause of your equipment going up in smoke - that would be due to a faulty component or user error.

Irrespective of the previous mention of vendor rating methods it only takes milliseconds for components to get damaged.
 

bazelio

Well-Known Member
Sep 27, 2016
1,480
759
215
California
If SR fuses are going pop with regular start up surges but generics don’t, then their actual rating is lower than what is printed on them. Ergo, you are not actually going out of tolerance.

If however you do go outside of tolerance, then the higher rated fuse will blow a few milliseconds later. This advise was actually given to me by a valve amp builder.

Neither of these would however be the cause of your equipment going up in smoke - that would be due to a faulty component or user error.

Or the tolerances are very poor on the SR fuses, in which case increasing to some higher (unknown) amperage rating isn't really advisable since a tolerance is +/-. Why doesn't the valve amp builder use a CL90 to avoid the startup surge rather than recommending fuses that can overcome it? In any event, the best suggestion IMO is to use fuses that actually work at their rated spec. If SR fuses do not, then consider using a better fuse. Even the IEC doesn't do well with repeated high current surges over time.
 

highstream

Well-Known Member
Nov 16, 2013
347
120
273
But then you have the case of Lampi's dacs, where the back panel says 1.6A slow blow (U.S.), the owner in Poland by email says 2A, while the importers (LampiNA), who have to deal with customers' popping fuses, say they use 3.15A.
 

David Pritchard

New Member
Nov 5, 2015
11
6
3
I have recently compared the SR Blue fuse, SR Orange fuse, and factory stock fuse in my Pass Labs INT-60 amplifier. I am impressed with the sonic improvement using the Orange fuse. After initial installation there was an immediate difference, and then a continued change at 1 day, 3 days, and at 10 days. The experiment was repeated at day 10 and the difference between the Orange fuse and factory stock fuse was even more pronounced. The fuse should be tried in both directions as there is a difference in sound . Next experiments I will be evaluating the Orange fuse in my Pass Labs HP-1 headphone amp and my Pass Labs First Watt- F7 amp. It is a fun and easy experiment to do, and the fuse can be returned if one does not think the sonic change is worthwhile. It is a lot easier than tube rolling my SET amps!
David Pritchard
 
  • Like
Reactions: johndoe21ro

SR-1

Well-Known Member
Sep 3, 2016
32
0
86
London, United Kingdom
I have recently compared the SR Blue fuse, SR Orange fuse, and factory stock fuse in my Pass Labs INT-60 amplifier. I am impressed with the sonic improvement using the Orange fuse. After initial installation there was an immediate difference, and then a continued change at 1 day, 3 days, and at 10 days. The experiment was repeated at day 10 and the difference between the Orange fuse and factory stock fuse was even more pronounced. The fuse should be tried in both directions as there is a difference in sound . Next experiments I will be evaluating the Orange fuse in my Pass Labs HP-1 headphone amp and my Pass Labs First Watt- F7 amp. It is a fun and easy experiment to do, and the fuse can be returned if one does not think the sonic change is worthwhile. It is a lot easier than tube rolling my SET amps!
David Pritchard
How would you characterise the “sonic improvement”?
 

David Pritchard

New Member
Nov 5, 2015
11
6
3
With the Orange fuse I heard the following changes:
The soundstage was more three dimensional. The location of each instrument was more clearly defined. The harmonics were richer and more complex. The reverberant sound of the recording location was more detailed. Lead vocals were more detailed yet not thin. Overall the sound had better flow and more information. The music listening experience is more satisfying.
David Pritchard
 
  • Like
Reactions: SR-1

IanG-UK

Well-Known Member
Apr 11, 2011
245
40
123
This debate makes one think whether, with the orange fuse being "way ahead" of the blue fuse, someone with an enthusiasm for these things should try connecting two orange-fused plugs in series and see if the sound is better still.
 

David Pritchard

New Member
Nov 5, 2015
11
6
3
bazelio:
I did directly compare the Synergistic Research Orange fuse to a brand new Bussman fuse. Same values. With the Orange fuse the Pass Labs amplifier sounde better. If you would like to send me the fuse you have listed, I am glad to also compare it to the Orange fuse.
David Pritchard
2882 North Roadrunner Pky
H-214
Las Cruces, New Mexico 88011
 

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. A place where audiophiles and audio companies discuss existing and new audio products, music servers, music streamers and computer audio, digital to audio convertors (DACS), turntables, phono stages, cartridges, reel to reel, speakers, headphones, tube amplifiers and solid state amplification. Founded in 2010 What's Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals we enjoy learning about new things and meeting new people and participating in spirited debates.

Quick Navigation

User Menu

Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing