voltage drop

[ThSpeakerDude88]

hehe! ok, so I came up with 333 ohms and 1.2 watts, so a 330 ohm 2w resistor should work, right?

and if I want to run it at the lower voltage, a 450 ohm 2 watt.

Boy this is fun! thanks for showing me how to do this!

 

[ThSpeakerDude88]

by the way, is the wattage dissipated in the resistor what my amp will lose as far as supply power?

 

[homer09]

your calculations all look good to me

your amp will lose the current that your fan draws. in this case it will lose 160mA. so its like your power supply is now 780mA. if your amp never needs to draw more than 780mA, you shouldnt notice a difference, if it needs to, then yes, you amp will be robbed of power.

 

[AudioFreak]

homer,

TSD88's last post regarding fans specs states 60mA so he's only down to 880mA on the supply which is still very low tho not much lower than the 940mA he's starting with.

 

[ThSpeakerDude88]

yeah I really need to look into the 48 volt psu's i see at partsexpress. Although they say the current rating is unknown... o well. Hey know where I can get a 48 volt tordial transformer? or better yet a 48v center tapped?

 

[homer09]

homer,

TSD88's last post regarding fans specs states 60mA so he's only down to 880mA on the supply which is still very low tho not much lower than the 940mA he's starting with.

oops, my bad, thought it was .16 instead of .06

 

[ThSpeakerDude88]

haha well thats always good to know. Woo-hoo.. that means I'm down to 26 watts my amp can put out with the given psu. Man I reallllyyyy need a bigger psu!

 

[asgorath]

If you're using a power supply from a printer then you're not using a linear powre supply like most everyone on this board, but instead you're using a switching power supply. And my guess on top of that is a not so great switching power supply. Printers don't need super clean power so I bet that power supply is gonna add dirty sound to your amp and your amp won't end up sounding all that great.

If you want to use a switcher you might be able to, but I know these gainclones are very sensitive to how the power supply is built, so you will need to watch out on what you choose.

Also, to supress the EMI and EMF produced by DC brushless fans I imagine you could use a voltage regulator which would soak it up.

Here's an idea for ya

An externally hosted image should be here but it was not working when we last tested it.

For C1, use at least a 50V capacitor
For C2, use at least a 20V capacitor

 

[ThSpeakerDude88]

hmm ok. What vr do you reccomend? oh and by the way, my amp is very quiet even at full volume. no hiss no nothing, I mean dead silent.

 

[asgorath]

hmm ok. What vr do you reccomend? oh and by the way, my amp is very quiet even at full volume. no hiss no nothing, I mean dead silent.

I recommend the voltage regulator that I put in the schematic. Sheesh. lol. Oh, and be sure to heatsink it. That's a pretty large voltage drop you're asking it to do.

 

[ThSpeakerDude88]

HAHA WOW! I totally missed the number! my bad! sorry!