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Fuses

G

GruntPuppy

pfm Member
It was all working so beautifully... Subs and mains integrated nicely, musical, good soundstage, I was happy as a pig in poop.

Then something went pop, and there was no sound. Nothing. Since I'm running two power amps off a pre, this pointed to the pre or the source. The source was a satellite box at the time, which worked fine direct to the tv. Which led to believe my pre-amp had gone "pop." No sign on the remote, screen or settings of any malfunction, but no sound output to the power amps.

I was that upset, I turned it all off for a day and sulked. Even the dog left me alone.

Coming back to it today, I noted that a single fuse in my bass power amp had gone pop... a 3a fuse. My pre must have some sort of cut-out to prevent further possible damage in the event of an amp failure. I've got my cable chap booked for the end of the month, covid allowing, and I'll be making sure all the custom power leads have the appropriate fuses on board - 5a in the case of the 545-ii, apparently. When I set the amp up, I just grabbed a cable, I didn't think to check the fuse rating at the time. I thought I'd lost the heart of my system, and having struggled to get the kit I've put together that would have been a death blow to the efforts.
 
Unlikely for a power amp blow to affect the pre, but you maybe have an odd system there. I learnt to my cost the difference between T (anti-surge) and F (quick-blow), Just stick a rated fuse of the correct type in it, if what Simon says is the cause.

5A seems quite high, but maybe you have powerful mono's.
 
GruntPuppy said:
It was all working so beautifully... Subs and mains integrated nicely, musical, good soundstage, I was happy as a pig in poop.

Then something went pop, and there was no sound. Nothing. Since I'm running two power amps off a pre, this pointed to the pre or the source. The source was a satellite box at the time, which worked fine direct to the tv. Which led to believe my pre-amp had gone "pop." No sign on the remote, screen or settings of any malfunction, but no sound output to the power amps.

I was that upset, I turned it all off for a day and sulked. Even the dog left me alone.

Coming back to it today, I noted that a single fuse in my bass power amp had gone pop... a 3a fuse. My pre must have some sort of cut-out to prevent further possible damage in the event of an amp failure. I've got my cable chap booked for the end of the month, covid allowing, and I'll be making sure all the custom power leads have the appropriate fuses on board - 5a in the case of the 545-ii, apparently. When I set the amp up, I just grabbed a cable, I didn't think to check the fuse rating at the time. I thought I'd lost the heart of my system, and having struggled to get the kit I've put together that would have been a death blow to the efforts.
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If these be Adcom GFA-545 II then for 220-240VAC usage the mains inlet fuses need be fast blow 4A/250V (i.e. the fuses within the fuse sockets round back of the amps). These shouldn't be confused with UK mains plug fuses which are primarily intended to protect the mains cord between the mains plug and appliance during fault conditions (as well as afford some protection with none fused appliances such as lamps, etc.).
 
Craig B said:
If these be Adcom GFA-545 II then for 220-240VAC usage the mains inlet fuses need be fast blow 4A/250V (i.e. the fuses within the fuse sockets round back of the amps). These shouldn't be confused with UK mains plug fuses which are primarily intended to protect the mains cord between the mains plug and appliance during fault conditions (as well as afford some protection with none fused appliances such as lamps, etc.).
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Yep, them's the buggers - the inlet fuses. According to the man himself, Nelson Pass, 5a ceramics are a significant increase in sound quality there. Still to do, mind you. Might have a look for a 4a ceramic.

The thought of changing a quick blow for a slow blow does give me some concerns, mind you.
 
Mike Reed said:
Unlikely for a power amp blow to affect the pre, but you maybe have an odd system there. I learnt to my cost the difference between T (anti-surge) and F (quick-blow), Just stick a rated fuse of the correct type in it, if what Simon says is the cause.

5A seems quite high, but maybe you have powerful mono's.
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I have an extremely odd system! Pre amp driving 2 power amps, 1 for the bass subs, 1 for main speakers. I thought it was because I'd committed one of the cardinal sins - unplugging (rca) a turned-on power amp. Either way, I'm so glad that things are back where I can continue experimenting with the cables (speaker and RCA) for final configuration.

The amp in question is only 130wpc @ 8 ohms, if it had been the other amp I would have been unconsolable.
 
GruntPuppy said:
The thought of changing a quick blow for a slow blow does give me some concerns, mind you.
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Guess you stick to the type recommended/in there already. My s/s amplification has always had fast-blow, so I was unused to valved amps requiring anti-surge (slow-blow), as inital power requirements are high upon fire-up but not normally.
 
Mike Reed said:
Guess you stick to the type recommended/in there already. My s/s amplification has always had fast-blow, so I was unused to valved amps requiring anti-surge (slow-blow), as inital power requirements are high upon fire-up but not normally.
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Are anti-surge fuses slow-blow? I assumed a surge was a transient event that would not last long enough to stress a slow-blow fuse.
 
ToTo Man said:
Are anti-surge fuses slow-blow? I assumed a surge was a transient event that would not last long enough to stress a slow-blow fuse.
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I thought, from what I read when sourcing fuses, that they were one and the same. As the transient surge is upon start-up, slow-blow contains this, whereas fast-blow fuses don't.
 
GruntPuppy said:
Yep, them's the buggers - the inlet fuses. According to the man himself, Nelson Pass, 5a ceramics are a significant increase in sound quality there. Still to do, mind you. Might have a look for a 4a ceramic.

The thought of changing a quick blow for a slow blow does give me some concerns, mind you.
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Mr. Pass would have been referring to 120VAC mains usage here. Adcom specified 6A/125V (Bel) or 6A/250V (Bussmann, Littelfuse) fast blow for usage over here in North America.
 
I think I found a middle ground - an "audiophile" fuse that matches the original - a 4.0a quick blow. For £18, as an amp mod it's a no-brainer to try. OK, it's not the ceramic that Nelson Pass suggested, but I figure it's worth a shot at that price.
 
There is no such thing as an 'audiophile' fuse. That isn't to say that there does not exist deluded audiophiles.

You can get a 10pk of ceramic cartridge 4A/250V, speed F, 5 x 20mm fuses from RS for £1.62.
 
Craig B said:
There is no such thing as an 'audiophile' fuse. That isn't to say that there does not exist deluded audiophiles.

You can get a 10pk of ceramic cartridge 4A/250V, speed F, 5 x 20mm fuses from RS for £1.62.
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I was planning on staying quick blow, and I can point you to someone who can audibly demonstrate the difference between fuses on their system.
 
Craig B said:
There is no such thing as an 'audiophile' fuse.
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Conversely, there seems to quite a choice, Craig, but whether there's any sonic benefit is another matter. I suppose it's logical that a better made fuse is likely to be a physical improvement, and by association, more likely to represent a better 'flow' of electricity plus longevity in fluctuating mains supply conditions.

Jez Arkless of this parish is of the opinion that one fuse is as good as another ('more or less'; sic), but that's par for the course !

I've no experience in experimenting with quality/audiophile/ unicorn hair fuses, but I can attest to the difference in performance (with Naim amplification and a Meridian CDP) by upping the fuse rating and indeed by not having a fuse at all, but (a) that's very dodgy indeed, and (b) was a limited experiment in zealous audiophile days. That a 5 or 6 amp fuse is recommended is more than adequate, compared to the 1.5 to 3 amp fuses generally seen.

If Nelson Pass recommended ceramic fuses over common or garden glass ones, I guess he thinks there ARE differences in fuses, but possibly because of the quality of manufacture rather than controversial sonic improvements (which may equate to the same thing?); this would make sense to me.
 
Mike Reed said:
Conversely, there seems to quite a choice, Craig, but whether there's any sonic benefit is another matter. I suppose it's logical that a better made fuse is likely to be a physical improvement, and by association, more likely to represent a better 'flow' of electricity plus longevity in fluctuating mains supply conditions.

Jez Arkless of this parish is of the opinion that one fuse is as good as another ('more or less'; sic), but that's par for the course !

I've no experience in experimenting with quality/audiophile/ unicorn hair fuses, but I can attest to the difference in performance (with Naim amplification and a Meridian CDP) by upping the fuse rating and indeed by not having a fuse at all, but (a) that's very dodgy indeed, and (b) was a limited experiment in zealous audiophile days. That a 5 or 6 amp fuse is recommended is more than adequate, compared to the 1.5 to 3 amp fuses generally seen.

If Nelson Pass recommended ceramic fuses over common or garden glass ones, I guess he thinks there ARE differences in fuses, but possibly because of the quality of manufacture rather than controversial sonic improvements (which may equate to the same thing?); this would make sense to me.
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Hello Mike,

When dealing with safety features such as fuses, it is very important to distinguish between mains input fuses and those that may be in series with such as the internal supply rails and/or output/speaker protection.

From Nelson Pass himself, in reply to a bodger's inquiry regarding potential fuse substitutes within an Adcom amplifier...

""I don't know offhand, but there is resistance and signal modulation in the fuses, and the bigger the value of the fuse, the less of that you'll see. Another possibility is that one or more of the fuse connectors was oxidized or dirty, which really degrades the connection, in which case new fuses might have cured that.

"Probably 1 of the fuses is the AC line fuse, which I would not fool with further, but the remaining are in series with the supply rails of each channel. You might consider bypassing those with wire."
​
If one's fuse has blown, and one wants better quality, then buy Bussmann, Littelfuse or Bel brand; just make sure not to change the value of a mains inlet fuse.

Craig
 
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Craig B said:
If one's fuse has blown, and one wants better quality, then buy Bussmann, Littelfuse or Bel brand; just make sure not to change the value of a mains inlet fuse
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Ta for the tip re. better quality fuses, Craig, as I need to get in a spare or two (of T fuses).
 
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