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!
Have you tried contacting the maker of the fuse and asking why their product is acting differently than the "std" fuse?

The maker/vendor usually knows best.

It sounds like the Psvane tubes are the culprit as you suspect.

Like Andrew ( Mapman ) suggested, you need to find out if the Hi-Fi Tuning fuses are simply made to a tighter spec.

I'd also talk to Mac and someone knowledgeable about the different tubes. Are the Psvane tubes able to be used in your amp safely? If they're drawing more current, could that be detrimental in some way?

Try biasing them to lowest parameter reccomended.
Are you sure you are not confusing a slow-blo fuse with a standard one?
This is not true in my system!!
Are you sure that the fuse rating are exactly the same? Some 2 amp are 250 volts and some are 125 volts! Do you really hear a difference with the fuses? If not just go back to the standard ones and avoid the problem!
My Zana Deux OTL headphone amp had the same problem. I discussed this with Craig Uthus the amp designer who had me go to the next size up in fuse value. I went from a 2.5 to 3 amp rating. My blow fuses ocurred at start up or shortly there after. This ocurred after some tube rolling.
Thank you all for the input.

Yogiboy: both are rated 250V. Moreover, the first hi-end fuse that blew had been running for over a year prior to rolling tubes.

Hifiharv: I'm sure I'm not confusing those. Both are slow blow.

Schubert: good idea. Unfortunately my amp is auto-biasing, though.

Mapman and Krell_man: that's probably the most sensible route, and in line with Davidpritchard's experience. With McIntosh I hesitate a bit to request advice because it's such a large company. But will do and will post their answer for others to benefit too.

Like Andrew ( Mapman ) suggested, you need to find out if the Hi-Fi Tuning fuses are simply made to a tighter spec.


Or maybe made to a looser spec?
Who made the stock tubes? I think the tube they use now is the Gold Lion (Russian) KT-88. That is a very good tube especially if you like a warm tone. I thought they were fabulous in my Jadis, but it may not be your cup o tea. McIntosh certainly approves them so they shouldn't blow any fuses.
I had my first audiophile fuse blow in my tube integrated within a few days (hi fi tuning silver star). I started doing some research on some of the other brands and found one that said in small print at the bottom of the ad that it was not designed (and I can't remember the exact words)to be installed directly in the AC path or something like that? My fuse is in the little drawer under the IEC. Never had a problem with stock fuses. I have tried to find that disclaimer again to no avail. I know some of them specifically mention use for mains power and not sure which one the OP used that blew but thought I'd mention that. I'd contact the manufacturer and tell them exactly how one intends to use it before spending $50.
I asked McIntosh...

"We do not recommend the ‘high –end’ super fuses… it is impossible for them to improve sound and it may be causing your problem.
But any amp that blows fuses should have all the tubes tested."

So I learnt I'm delusional since I hear an improvement in sound with hi-end fuses, and my tubes must be bad even though they are not blowing up standard fuses.

Unfortunately this manufacturer is not helpful.

Any other ideas?
You need to get rid of the McIntosh and get an amp from a manufacturer who understands and supports aftermarket fuses.
Good idea.
Change $5000 amplifier for a $25 fuse.
Those two sentences from McIntosh seem perfectly reasonable coming from the manufacturer of any amp.
Those two sentences seem to indicate total ignorance, from the manufacturer of any amp. Not surprising, from those with the hubris of McIntrash. Of course; that's just my own personal opinion, based on personal experience with both.
I'm interested to hear what the fuse maker says.
McIntosh's advice to check tubes if fuses are blowing in general is hard to argue with.

No vendor will support a product that the user has altered. Right or wrong, if the vendor has doubt about use of any part introduced by a third party, including a fuse, for whatever reason, including lack of information, they are NOT going to recommend it and then be obligated to support that recommendation.

Also, the comment about whether the fuse can sound better or not might be a bit strong, but I'd have to take the position that the purpose of a fuse device is NOT to make something sound better, even if in fact it does. THere are many other ways for a product to accomplish that. If there is any question about the product being able to serve its primary function, which in this case is to PROTECT the gear, not make it sound better, then a no confidence confidence vote for that part in a case like this which seems to support that concern is not surprising.

That response increases my confidence in McIntosh support, it does not decrease it.

SO there is a choice to be made. Making sure the tubes are in good working order would seem to be a logical next step. One or more sub par tubes may well result in lesser performance and/or other issues, regardless of fuse used. Having tubes all in good working order is paramount to a tube device working as it should. Flavor of correct fuse used matters so much less, to the extent it even matters at all, that it is a no brainer which to address first.
Excellent response Mapman.
If both the standard and upgrade fuses were blowing, the
tubes would be the first thing I would suspect and test.
Since only the upgrades are going, and especially given that
the tubes are new(not that new tubes don't/can't cause
problems), I wouldn't waste my time there. Personally; I'm
using eight(what were NOS) GE 6550A output tubes, in my
Cary's. I've had two Hi-Fi Tuning Supreme fuses go out in
the(fixed)bias protection holder(one each amp over the
course of 30 days). I'm still using Supremes in the mains,
but- though I really like the more natural presentation of
the upgraded fuses; I can't afford slightly over $90 a
pop(literally), for the bias circuit. I tried a pair of
Synergistic Research Quantums in the amps and they held
fine(didn't care for the sound). Reinstalled a Littelfuse
pair of the same value, a couple months ago and no problems.
Has anyone mentioned that Hi-Fi Tuning Supremes are rated
250V, Synergistic's are rated 500V, and many output tubes
use 400 to 450V, plate voltage? That would only
matter in one's bias protection circuit, of course.
I have Acoustat tube servo amps with lethal voltages,made in the 1970's but modiffied.
There are 4 tubes in each amp,sourced from television technology because of the demands made on such a circuit.The amps also are the source of power to charge the electrostatic panels and keep them charged, they are not just "power amps",but made specifically for the Acoustat X series.They are not a conventional amplifier design.

The amps are always "on",but in a sleep mode until I flip the toggle switches for listening, and then off when I'm done.So there's a lot of juice flowing thru those fuses.

I've been using upgraded fuses(HiFi Supremes-4) in them for two years and never had one blow on me , except when it was an error on my part.

That the upgraded fuses are blowing and the stock fuses are not would indicate to me that the stock fuses are more forgiving and the upgraded fuses are only doing what they are supposed to do-self destruct before something awful happens.
I would stick with the stock fuses and the new tubes and cross my fingers, or go back to the stock tubes and the upgraded fuses.

I am curious.
What made the most enjoyable improvement, the upgraded fuses or the upgraded tubes?
The answer to that should settle it.
"That the upgraded fuses are blowing and the stock fuses are not would indicate to me that the stock fuses are more forgiving and the upgraded fuses are only doing what they are supposed to do-self destruct before something awful happens."

You could just as easily assume that the stock fuses are doing exactly what they should be doing and the upgrades are much too sensitive or not up to spec.
I couldn't find a way to contact HiFi Tuning Fuses so I asked The Cable Company, from whom I bought the fuses:

"I think that you have hit the nail on the head. The HiFi Tuning fuses are EXACT-rated fuses while off-the-shelf fuses are +10% tolerance which means that they would actually be 2.2A out of the box. The PsVane tubes additional current draw appears to work with that window while the HiFi Tuning fuses blow. This WILL happen again with these tubes, so your hesitancy in installing the new fuses was a good thing."

They don't sell any 5x20 slo-blo hi-end fuses in 2.2A, or any other rating between 2A (what I tried) and 2.5A. While the technician thought 2.5A wouldn't be risky, I'm rather reluctant to do that.

BTW, Lacee asked whether upgraded tubes or fuses made the largest impact. Tubes, for sure. But when I had stock KT88 and introduced an upgraded fuse I did hear an improvement. So now I want the cake and eat it :-)
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.
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.