Computer SMPS and Gainclone

soundNERD · 20th January 2004, 01:12 AM

Can I take a standard computer SMPS, tie the + 5 and +12 wires together, the -5 and -12 wires together, and use them to power a gainclone at +-17VDC?

I have an old AT style supply that can produce 250W, so that could easily power a 3886 or 2 or something similar up to its full power.

Will this work?

Thanks, Mike

neutron7 · 20th January 2004, 01:22 AM

no you can not do that because both voltages are referenced to the same ground. if you connected them together then you would probably blow the 12 or 5 volt lines (or both) or at least short circuit protection would trigger.

also you need complimentary positive and negative power rails for LM 38xx type amps.

If you want to use a computer PSU for an amplifier you could use the TDA7374 which is designed for car radios. so it will work on 12 volts. Dont expect any astounding sound quality out of it either (esp with comp PSU)

soundNERD · 20th January 2004, 01:44 AM

Will a 3886 run off of a 24V supply?

If so, I could connect the +-12 and gnd to the chip, right?

or am i missing something?

-Mike

li_gangyi · 20th January 2004, 05:05 AM

the negative 12V is rated at an amp due to it being provided by a 7912 regulator...I dun think u'll be able to power ur amp that way...

microJean · 20th January 2004, 07:10 AM

The -12V can supply only 500mA so you can use it only with a headphone

neutron7 · 20th January 2004, 07:45 AM

It is a really low voltage to run it from. it will probably work though because the lm3886 will only put out 10 watts at that supply voltage (at 4 ohms) and only about 5 watts at 8 ohms.

(see page 14)
http://www.national.com/ds/LM/LM3886.pdf

so if my guesstimations are correct that is less than one amp being drawn from negative rail.

soundNERD · 20th January 2004, 11:53 AM

OK, well thanks anyway, I just found the old supply sitting around and thought i could put it to good use. Since it was a 250W, I thought I could get more power out of it.

Thanks anyway, Mike

tifosi_f1 · 21st January 2004, 05:42 PM

If you dont decide to use the power supply itself, you could do as I plan to do and use the metal box from the psu to house your gainclone (minus psu bits inside, of course). It should have a nice dual pole switch and some vent holes - and as its metal you can mount your chip(s) to it as long as you insulate them

Then just spraypaint it your desired colour....

I'll post some pics of my one once I've finished.

soundNERD · 21st January 2004, 08:45 PM

Yes, I am going to do that. Not with that supply though. I have a broken dell atx supply, and tore out all except the fan. The only switch on it, though, is the voltage selector switch, so it won't work for that. But it does have a nice fan and power cord connector.

-Mike

Tensop · 22nd January 2004, 10:55 AM

You can disconnect the Ground reference point (chassis connections) on a computer power supply and supply it with +12v from another computer power supply. As you can have these amplifiers in single ended mode you could chain 3 or 4 computer power supplies in series.

for 3 computer powersupplies its potential from ground on PSU#1 to +12 on PSU#3 would be 36 volts, and depending on the PSUs's used you would have roughly 36 volts @ 10 amps.. 360 watts. You can also adjust the output voltage on the power supplies, up to around 14 volts. giving you 42 volts. ofcourse 42 volts into a single ended amplifier @ 8 ohms is only going to give you around ~20 watts audio power

20th January 2004, 05:05 AM	#4
li_gangyi diyAudio Member Join Date: Jun 2003 Location: Woodlands Circle	the negative 12V is rated at an amp due to it being provided by a 7912 regulator...I dun think u'll be able to power ur amp that way... __________________ Kids in the back seat cause accidents...Accidents in the back seat cause kids...

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
My New 12V SMPS w/Computer PSU Transformer	EWorkshop1708	Power Supplies	31	9th March 2010 10:56 AM
Car computer SMPS	xplod1236	Power Supplies	2	1st April 2009 02:45 AM
Computer SMPS X'mer material	arif__anwar	Power Supplies	5	8th April 2008 12:46 PM
converting a computer smps to a class d amp	Tekko	Class D	9	8th August 2005 01:36 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

20th January 2004, 01:12 AM	#1
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	Computer SMPS and Gainclone Can I take a standard computer SMPS, tie the + 5 and +12 wires together, the -5 and -12 wires together, and use them to power a gainclone at +-17VDC? I have an old AT style supply that can produce 250W, so that could easily power a 3886 or 2 or something similar up to its full power. Will this work? Thanks, Mike

20th January 2004, 01:22 AM	#2
neutron7 diyAudio Member Join Date: Dec 2003 Location: Toronto Canada	no you can not do that because both voltages are referenced to the same ground. if you connected them together then you would probably blow the 12 or 5 volt lines (or both) or at least short circuit protection would trigger. also you need complimentary positive and negative power rails for LM 38xx type amps. If you want to use a computer PSU for an amplifier you could use the TDA7374 which is designed for car radios. so it will work on 12 volts. Dont expect any astounding sound quality out of it either (esp with comp PSU)

20th January 2004, 01:44 AM	#3
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	Will a 3886 run off of a 24V supply? If so, I could connect the +-12 and gnd to the chip, right? or am i missing something? -Mike

20th January 2004, 07:10 AM	#5
microJean diyAudio Member Join Date: Dec 2003 Location: Romania	The -12V can supply only 500mA so you can use it only with a headphone

20th January 2004, 07:45 AM	#6
neutron7 diyAudio Member Join Date: Dec 2003 Location: Toronto Canada	It is a really low voltage to run it from. it will probably work though because the lm3886 will only put out 10 watts at that supply voltage (at 4 ohms) and only about 5 watts at 8 ohms. (see page 14) http://www.national.com/ds/LM/LM3886.pdf so if my guesstimations are correct that is less than one amp being drawn from negative rail.

20th January 2004, 11:53 AM	#7
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	OK, well thanks anyway, I just found the old supply sitting around and thought i could put it to good use. Since it was a 250W, I thought I could get more power out of it. Thanks anyway, Mike

21st January 2004, 05:42 PM	#8
tifosi_f1 diyAudio Member Join Date: Jan 2004 Location: British Isles	If you dont decide to use the power supply itself, you could do as I plan to do and use the metal box from the psu to house your gainclone (minus psu bits inside, of course). It should have a nice dual pole switch and some vent holes - and as its metal you can mount your chip(s) to it as long as you insulate them Then just spraypaint it your desired colour.... I'll post some pics of my one once I've finished.

21st January 2004, 08:45 PM	#9
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	Yes, I am going to do that. Not with that supply though. I have a broken dell atx supply, and tore out all except the fan. The only switch on it, though, is the voltage selector switch, so it won't work for that. But it does have a nice fan and power cord connector. -Mike

22nd January 2004, 10:55 AM	#10
Tensop diyAudio Member Join Date: Jul 2003 Location: Chapel St.	You can disconnect the Ground reference point (chassis connections) on a computer power supply and supply it with +12v from another computer power supply. As you can have these amplifiers in single ended mode you could chain 3 or 4 computer power supplies in series. for 3 computer powersupplies its potential from ground on PSU#1 to +12 on PSU#3 would be 36 volts, and depending on the PSUs's used you would have roughly 36 volts @ 10 amps.. 360 watts. You can also adjust the output voltage on the power supplies, up to around 14 volts. giving you 42 volts. ofcourse 42 volts into a single ended amplifier @ 8 ohms is only going to give you around ~20 watts audio power

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)