Lemon HiFi-Tuning Fuse?

After researching the cause, I can find no reason why my HiFi-Tuning fuse simply blew in my Boulder L3AE line stage.

This was at first scary, because I had my line stage serviced and recapped last year by Boulder Amplifiers. When the fuse blew, I got that usual sinking feeling, but after replacing the HiFi-Tuning fuse (1A, 500v) with the original Boulder fuse (1A, 250v), no problems.

My power is also stable. And, I have my Boulder line stage plugged into a Brick Wall surge protector that is shared with my TT motor controller. The motor controller is just fine, so no issues there.

Has anyone experienced these fuses just giving out? I've only had my fuse for about a year, so could this just be a lemon?


The fuse itself might have had a short.....every company has a substandard product from time to time.

Thanks, I was just making sure that I wasn't missing something, since I do use the fuses in some of my other gear without encountering this problem.


I'm sure it's just a one-off. I've got about 6 of them in my components and they've been fine for a few years so far. Knock on wood.

All the best,
Do you know if the Hi-Fi Tuning was a fast-blo? It could be too much inrush current.
Even "non-audiophile" fuses give up sometimes after a period of use.  I've had Buss and Littelfuses pop for no apparent reason.  Replaced them, and things were fine forever after.  I certainly wouldn't worry about it so long as a replacement fuse doesn't blow quickly (which might then indicate an issue with the component).

"Even "non-audiophile" fuses give up sometimes after a period of use. I've had Buss and Littelfuses pop for no apparent reason."

I suspect it's safe to assume that happens a hundred times more often than for aftermarket audiophile fuses.

Thanks, everyone.

I'm now wondering if it may have been caused by static? We have low humidity here in Colorado, and frequently I get a spark when grabbing the volume control of the line stage. More so, than my other components. I'll try grounding the unit, because the power cord is a built-in two prong job. A humidifier may also help.


There are/is a thread on this issue with the recommendation of using a rating above the replaced original. 
I read a post saying that, I should be fine with the HiFi Tuning 500v rating over the original 250v rating because the current rating is the same. The fuse is a fast blow version, so the same as the original.
A fast blow fuse as a AC mains fuse feeding a presumably linear power supply (Transformer/ Diode Bridge/ Capacitor) is highly unlikely,  much more common is a slow blow for this application, your original fuse will have some letter stamped into the end cap identifying if its a slow blow or a fast blow.

Good Listening


Kenny, Noromance may be referring to the ongoing "Synergistic Red Fuse" thread, in which several people reported experiencing false blows (fuses blowing unnecessarily) with some SR fuses in some equipment. I and others therefore suggested using SR fuses having a current rating one or possibly two rating increments higher than the current rating of the stock fuse. I have no idea as to whether or not that may be applicable in the case of HiFi Tuning fuses.

The voltage rating difference you referred to is a different matter. And everything else being equal a rating of 500V is actually better than a rating of 250V, although as a practical matter it is unlikely to make any difference in a 120V application. The significance of the voltage rating is that when the fuse **should** blow if that rating is lower than the applied voltage the fuse might not open the circuit properly (i.e., it might continue to conduct current). Or it might rupture or explode.

Also, the only time a fuse will "see" those kinds of high voltages will be when a mains fuse (or a fuse that is in some other high voltage circuit) has blown or is in the process of blowing. Under normal operating conditions the voltage between the two terminals of a fuse will be a small fraction of a volt, regardless of the voltage that is applied to the circuit.

-- Al

Thanks, guys. Well, looks like the two fuses are not the same, but still weird. The HiFi Tuning fuse is a slow blow, because I found the T designation. This is the fuse that blew. The original fuse has an F stamped on it, so it's a fast blow.
Different manufactures have different codes for fast blow and slow blow, the letters F and T does not automatically mean Fast  or Slow.  

As stated earlier it is most likely a slow blow fuse thats employed as the mains fuse in you Boulder preamp but you should consult with them.  FWIW I'd forget all about any aftermarket "hifi" fuses and go with a industrial grade fuse readily available form reputable suppliers like Mouser for an example.

Good Listening


Solved - The "T" designation is correct for slow blow from HiFi Tuning, and confirmed when I found my sales receipt. The "T" actually means timed, or the technical meaning for slow blow. I contacted Boulder Amplifiers who told me the fuse should be slow blow, so the fast replacement fuse I'm using now is not correct, even though it's been working.
Considering, that the HiFi Tuning fuse was in there for at least a year before it blew, and a fast replacement tube has been working just fine for over a week, it makes sense for me to conclude what stringreen and others have suggested, that the fuse may simply be sub-standard.
Time to order a new fuse.