A21 Problem

[songsmith7]

I bought this amp a week ago from a private owner and it performed great for 6 days. This morning when I powered it up I got no blue lights, a brighter P, and no sound at all. I checked the connections, all was in order. I replaced the XLR connections with RCAs and still nothing. I then hooked my speakers up to my EAD Powermaster 1000 and everything played fine. In the time I have had it, the unit has never been played louder than about 70 decibels, never clipped, nor been anything past lukewarm to the touch. So, in short, the thing powers up, but does not provide power to the speakers. Any ideas what the problem might be? Power supply? Fuse? Any help would be much appreciated!

[r100gs]

Check that the auto turn settings are correct if you are using that feature and also check that the gain control knobs did not get turned down.

[songsmith7]

Thanks, but I run manual on/off, and the gain controls remained at THX level. My speakers are the Monitor Audio Gold Ref 60's, not a particularly difficult speaker to drive. This is very frustrating, I thought Halos were built better than this. The unit had never been used prior to my buying it, too, so it's not like the previous owner was cranking it up.

[r100gs]

Is your on/off power button red instead of blue? Nice speakers by the way. :T

[songsmith7]

Thanks for the compliment!

I humbly retract everything I just said. I called Tony at Technical Support, and told him of my symptoms. A split -econd later, he told me it was a blown fuse. I just ran down to the electrical supply store and, voila, she's up and running again. Much relief here. On a side note, Tony said that I might try using a 15a fuse instead of a 12a like the unit recommends. What is rationale for this? He said the warranty would not be voided if one does this. Weird.

[Chris D]

Hey, songsmith, welcome to the Guide and Club Parasound! :banana: Good to hear everything got fixed with a simple fuse. Tony knows his stuff, so if he told you a 15A fuse would be okay, you're good to go. He must know that the unit can handle more power input than the original 12A they put in there.

[songsmith7]

Sweet, thanks Chris. I'm gonna buy a 15a Hi-Fi tuning fuse to replace the replacement. It's $40, but, hey, the Halo is worth it.

[Peter Nielsen]

Tony said that I might try using a 15a fuse instead of a 12a like the unit recommends. What is rationale for this? He said the warranty would not be voided if one does this. Weird.

The difference between 12A and 15A is so small, that it has no practical effect in this case.

However, the IMPORTANT part is to make sure that the fuse is the SLOW BLOW type. The Parasound amps use toroidal transformers. When powering up a toroidal, there is a huge in-rush current that may well exceed 15A for a few milliseconds. A fast-blow type fuse may easily blow in this time, which is why you want a slow-blow type.

If you spend $$$ on an audio-grade fuse, make sure that you get the SLOW BLOW type. (Otherwise your investment may go up in smoke in no time :# ).

IMHO, a mains-side fuse does not need to be high-end HiFi quality. (These are better used for internal fuses and speaker fuses).

For a toroidal transformer, I would get one of those regular ceramic slow blow fuses and be done with it.

Radioshack # 270-1040 will work perfectly ($2.99 for a set of 4 fuses)

You need a fuse that can handle the toroidal rush currents. The aforementioned fuse is perfect for that purpose, and the ceramic filling is what helps it perform well. (HiFi-type fuses are usually not filled, and are usually fast-blow - not suitable for this purpose!)

Peter

[songsmith7]

Good info, Peter. I've already got about 8 Hi-Fi Tuning fuses in various components, and they're all slow-blow. The improvements in the components range from minimal (my transport) to huge (My EAD PM 1000 and my Benchmark DAC). Snake oil? To some, perhaps, but for me, a rabid tweak freak, it's worth it. Hi-Fi tuning sells fast-blow fuses as well, but what kind of audio-video application would one use that type for?

[Peter Nielsen]

Good info, Peter. I've already got about 8 Hi-Fi Tuning fuses in various components, and they're all slow-blow. The improvements in the components range from minimal (my transport) to huge (My EAD PM 1000 and my Benchmark DAC). Snake oil? To some, perhaps, but for me, a rabid tweak freak, it's worth it. Hi-Fi tuning sells fast-blow fuses as well, but what kind of audio-video application would one use that type for?

Fast-blow fuses are used where it is important that the fuse blows immediately if the current exceeds the maximum allowed current. For instance Magnepan protects its midrange and tweeter with fast-blow fuses.

Snake oil? I would not call it that. The expensive fuses we talk about are usually gold plated and manufactured with high precision. Whether you can hear a difference or not is subjective. The gold plating ensures that the fuse contacts don't oxidate, but if the fuse holder is a cheap tin plated type it may do no good. (It may actually make things worse, as tin+gold is not a good metal combination. Consider the analogy tin/gold plated SIMM modules/sockets in a PC. You would never put tin plated SIMMs in a gold socket or vice versa).

However, if the fuse holder is also gold plated (like in the Magnepan MG20.1s), it only makes sense to use a gold plated fuse to ensure ideal contact surfaces. I really think Magnepan should include gold plated fuses by default...

Peter

[songsmith7]

Thanks for the info. I treat the fuses with Caig Pro Gold and Silclear before installing them. It's amazing how many otherwise excellent components have cheap fuse holders.