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why do hi-end fuses keep blowing, while std don't?

I've had my McIntosh MC275 for several years running flawlesly. Up until last Nov I was using stock KT88 and rolled small tubes and had a Hi-Fi Tunning fuse without issues.

In Nov-13 I upgraded the KT-88 to Psvane black bottles measuring 60mA plate current. A few power-ons after I rolled the tubes, I turned on the amp to let it warm up, but returned to a blown fuse. I thought a tube might be bad so used a std fuse, but never had a problem again.

Two months ago I bought a new high-end fuse, replaced it, and soon thereafter the same happened: blown fuse. I replaced it with a std fuse again, which is still running.

So I want to upgrade the fuse, but chances are if I use the 2A fuse it will happen again. Yet I don't want to use a higher value fuse. I'm thinking the Psvanes might be drawing significantly more current than the stock KT88 and the Hi-Fi Tunning fuse might have a tighter spec, driving said fuses to fail while the std ones survive. Would you agree?

Suggestions as to how to resolve this?

thanks much!
lewinskih01
lacee
811 posts
 
Good news and good luck with the cake.
It's always great when things go the way you think they should.
We should now be able to forget about HiFi fuses being inferior to stock fuse at least for protection.
The next hurdle to jump is to somehow proving they sound better than stock fuses, but just for those who refuse to try them and let their ears decide.
hevac1
812 posts
 
The inrush rating may be higher with the standard fuse. I work in the HVAC/Controls and work with lots of fuses that have the same amperage rating but the inrush ratings vary a lot. If sold in the USA this data sheet must be available.
summercrema
5 posts
 
Hi Lewinskih01, have you found the reason causing the upgraded fuses to blow , I am in the same situation, I purchased Furutech  Pure Transmission and HiFi Tuning fuses ( same spec on both Slow blow 5x20mm 3.15A) unfortunately both did not last more than 4 days, good music improvement  while they were working though (soundstage, extension of tones , high and low  ) clean and clearer imaging. Tested with following singers CDs, Madaonna The immaculate collection, Dire Strait , Karen Souza Essentials, Kandace Springs Soul Eyes . Iam prepare to buy the fuses again as long as I can find the solution to the problem. 

I agree with what Hevac1 saying,  I have asked a friend to measure the loading on stock fuse and the upgrade fuses as a start ... 

If you guys already find a solution I like to hear about it , many thanks .

  

georgehifi's avatar
georgehifi
10,312 posts
 
why do hi-end fuses keep blowing, while std don’t?

Built in obsolescence, with less "blowing headroom" to get even more money out of the gullible.

Mains fuses have a limited amount of turn "on cycle surges" that harden/weaken/crystalise the fuse wire inside them, eventually they blow, always at "the turn on surge" just like incandescent light globes do, because turn on is the heaviest current a fuse sees.

A new fuse left getting older and older right.
https://ibb.co/zSRwTd1

Cheers George

lewinskih01 OP
909 posts
 
I didn’t bother further. What is reflected in the thread is what I did and learnt, so kept the std fuses and upgraded tubes which have been running for 5 years flawlessly.
The amp runs hotter with these tubes than with the original ones which has to translate into higher current draw. Per the Cable Co answer, std fuses have additional 10% tolerance which seems to be enough. I didn’t want to to go up 25% rating in the fuse from 2 to 2.5A as it seemed unsafe for the amp. So I let go of that part of my audio nervosa and lived happily ever after :-)

In the past years I turned into an active system where now the McIntosh is driving mids/treble and sees a lower demand so runs cooler again. Could try hi-fi fuses again but I’m not prepared to risk throwing away money, so I stayed out. Sound is great and I found areas for more significant upgrades to sound than fuses made, so went that route.

Cheers
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