voltage drop - Page 3

ThSpeakerDude88 · 19th July 2005, 05:00 PM

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 · 19th July 2005, 05:15 PM

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

homer09 · 19th July 2005, 05:58 PM

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 · 19th July 2005, 06:09 PM

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 · 19th July 2005, 06:23 PM

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 · 19th July 2005, 06:59 PM

Quote:

Originally posted by 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.

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

ThSpeakerDude88 · 19th July 2005, 07:31 PM

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 · 19th July 2005, 07:49 PM

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

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

ThSpeakerDude88 · 19th July 2005, 08:31 PM

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 · 19th July 2005, 08:35 PM

Quote:

Originally posted by 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.

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.

19th July 2005, 05:58 PM	#23
homer09 diyAudio Member Join Date: Jan 2004 Location: Montreal	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. __________________ Most people wouldn't know good music if it came up and bit them in the ***. - Frank Zappa

19th July 2005, 06:09 PM	#24
AudioFreak Warp Engineer On Holiday Join Date: Oct 2001 Location: Queensland, Australia	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. __________________ - Dan

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19th July 2005, 05:00 PM	#21
ThSpeakerDude88 diyAudio Member Join Date: Jun 2005 Location: USA	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!

19th July 2005, 05:15 PM	#22
ThSpeakerDude88 diyAudio Member Join Date: Jun 2005 Location: USA	by the way, is the wattage dissipated in the resistor what my amp will lose as far as supply power?

19th July 2005, 06:23 PM	#25
ThSpeakerDude88 diyAudio Member Join Date: Jun 2005 Location: USA	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?

19th July 2005, 07:31 PM	#27
ThSpeakerDude88 diyAudio Member Join Date: Jun 2005 Location: USA	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!

19th July 2005, 07:49 PM	#28
asgorath diyAudio Member Join Date: Jun 2005 Location: Seal Beach, CA	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 For C1, use at least a 50V capacitor For C2, use at least a 20V capacitor

19th July 2005, 08:31 PM	#29
ThSpeakerDude88 diyAudio Member Join Date: Jun 2005 Location: USA	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.