A surprising note about power supplies...

Post by **Eric D** » Fri Dec 18, 2009 11:53 am

I am testing a MS2250 (original) board mounted in a MS2125 heatsink (for testing reasons). I am listening to NIN at loud levels on a pair of 8 ohm speakers.

I have only a 15A fuse installed!

I have talked before how music draws a lot less current than sine waves do, and this would be a good example of that. So for those of you looking to get a power supply to run your amps on music, you don't need a huge one.

Now I realize I am not running a pair of 15" woofers off this amp, but still it is playing full range music at almost too loud to tolerate levels. Still pretty impressive if you ask me.

shaheen · Post by **shaheen** » Fri Dec 18, 2009 12:14 pm

It would , remember also that most fuses are rated at a value but need to exceed those values by 300% before they smoke them selves.

So you would nee a peak of at least 1 sec of a current draw of 45A to blow the fuse.

Also pretty sure that glass fuses are in most cases rated at 220V, this would also affect when a fuse blows.

Someone with higher intellegence can you confirm or deny this.

Post by **joerg** » Fri Dec 18, 2009 1:23 pm

I´m working on a dayli basis with fuses and all the electrical related stuff for automation systems installation. Wish i could write everything down here on my own but that would take forever. So here´s a quote from wiki.

The speed at which a fuse blows depends on how much current flows through it and the material of which the fuse is made. The operating time is not a fixed interval, but decreases as the current increases. Fuses have different characteristics of operating time compared to current, characterized as "fast-blow", "slow-blow" or "time-delay", according to time required to respond to an overcurrent condition. A standard fuse may require twice its rated current to open in one second, a fast-blow fuse may require twice its rated current to blow in 0.1 seconds, and a slow-blow fuse may require twice its rated current for tens of seconds to blow.

Fuse selection depends on the load's characteristics. Semiconductor devices may use a fast or ultrafast fuse since semiconductor devices heat rapidly when excess current flows. The fastest blowing fuses are designed for the most sensitive electrical equipment, where even a short exposure to an overload current could be very damaging. Normal fast-blow fuses are the most general purpose fuses. The time delay fuse (also known as anti-surge, or slow-blow) are designed to allow a current which is above the rated value of the fuse to flow for a short period of time without the fuse blowing. These types of fuse are used on equipment such as motors, which draw a large initial current for a few milliseconds after they have been switched on.

And here´s the link to wiki!
http://en.wikipedia.org/wiki/Fuse_(electrical)

marko · Post by **marko** » Sat Dec 19, 2009 12:26 am

i love that board layout eric, i wanna do the same in my garage instead of the spaghetti wiring mess i have

just need a decent psu to run everything!

lashlee · Post by **lashlee** » Sat Dec 19, 2009 4:33 pm

What size power supply are you using? I've got a 60 amp with two optimas as back up. I doubt I'll push anything hard, but I have been known to see how well an amp will hold up to some abuse!!

By the way, I like the wiring. I've been looking for a combo power and ground block like the streetwires pieces but I may end up using two separate blocks.

MW3 · Post by **MW3** » Sat Dec 19, 2009 7:26 pm

That's not a real test bench, way too clean!

Post by **Eric D** » Sat Dec 19, 2009 8:11 pm

I have dual 100A supplies wired in parallel for 200A of current. Each supply is on a separate 20A 115V line to my home breaker box, and they are on opposite phases, for load balancing.

Post by **ttocs** » Sat Dec 19, 2009 11:19 pm

slap an amp meter on that and see what it draws at 8 ohms, just curious..........

Post by **Eric D** » Sun Dec 20, 2009 8:48 am

I still have to buy an amp meter. I don't have $350 to spare at the moment, but it is high on my list of useful shop tools (right behind a belt sander).

Post by **mhyde71** » Sun Dec 20, 2009 9:16 am

SWEET! now if i could just get my shop that clean-
oh wait! i am doing powder coating!

Electronic(s) stuff still gets done in the house

MW3 · Post by **MW3** » Sun Dec 20, 2009 9:45 am

That is waaaayyy too anal. When do we see the after pics?

Looks killer.

lashlee · Post by **lashlee** » Sun Dec 20, 2009 2:16 pm

Fantastic. It looks great.

Pillow · Post by **Pillow** » Sun Dec 20, 2009 5:14 pm

That is a really nice workbench setup!

oldschoolfan · Post by **oldschoolfan** » Tue Dec 22, 2009 7:18 pm

My compliments on your set up, right down to the chains for shelf support. I am a big fan of detail.

KUB3 · Post by **KUB3** » Wed Dec 23, 2009 12:22 am

Very clean workspace!

I've almost finished converting our dusty garage into a clean white workshop room. I still need to put the flooring paint down though. It was a messy process to do, involving building my first brick wall, adding tons of insulation, hanging a ceiling, water proofing the floor and building up wood beams, plaster skimming etc. Worth it soon though, as I also hate working in a mess.

k2f-gold · Post by **k2f-gold** » Wed Dec 23, 2009 4:55 am

hi eric, can I know what power supply is that?

Post by **Eric D** » Wed Dec 23, 2009 5:40 am

Audio Authority 978-100. It requires a special 20A (115V) outlet (unless you cut the cord, but I highly suggest against that).

I am not done with my setup yet. The desk under it is temporary until I can start building a bench. I also plan to move the speakers down to ear level and off to the sides. They are too high and close together for critical listening of audio equipment.

I need to blend a LCD monitor into it as well, so I can run all my test equipment and see it closer too me.