I was wondering whether it would be possible to use a computer power supply unit for a gainclone or t-amp PSU. I have a number of old dead PCs and I have just removed the power supply from one of them and it gives the following specifications:
Input 200-240V~3A 50hz
Output: +12V / 13A, -5V/0.3A, +5V /25A, -12V/0.8A, +3.3V/20A, +5VSB/2A
250W max (+5V & +3.3V 150W max)
I am having trouble understanding the Volts/Amps combinations - why for example is the -12V only rated at 0.8A whereas the +12V is 13A. Also the output VA doesn't seem to match the input VA - is there something special/different about computer power supplies and if so does that make them unsuitable for audio purposes?
Any help understanding this would be appreciated...
Sean
Input 200-240V~3A 50hz
Output: +12V / 13A, -5V/0.3A, +5V /25A, -12V/0.8A, +3.3V/20A, +5VSB/2A
250W max (+5V & +3.3V 150W max)
I am having trouble understanding the Volts/Amps combinations - why for example is the -12V only rated at 0.8A whereas the +12V is 13A. Also the output VA doesn't seem to match the input VA - is there something special/different about computer power supplies and if so does that make them unsuitable for audio purposes?
Any help understanding this would be appreciated...
Sean
Check out Nuuk's Site......
I believe he has some info about switching supplies there
http://myweb.tiscali.co.uk/nuukspot/decdun/😀
I believe he has some info about switching supplies there
http://myweb.tiscali.co.uk/nuukspot/decdun/😀
The -12v isn't really used to power anything with a heavy consumption. The + voltages are what run most everything in the computer, so the -12 doesn't really need much current available.
It would take some fairly significant modification to get a solid -12v line out of it.
Also, it seems to be a fairly popular opinion that switching power supplies aren't good for audio. (probably accurate in most cases)
Actually, it takes some significant modification to get a solid +12v line out of them 😉
They normally regulate the + voltages from a matrix which is based on a fairly average load distribution.
for example, if you heavily load the 12V line with no load on the 5v line the 12v will usually be pulled down, and the pwm will see the voltage fall and will increase its pulse width, which will cause the 5v line to climb higher, until the matrix is at the right value.
You'll usually end up with 10v and 6.5v or something. Often there's overvoltage protection, so when one of the lines climbs too high, it'll just shut off.
I've modded supplies before for use as dc bench supplies, and they work quite well, but only once you've removed the unnecessary bits, and then changed the resistor divider so it regulates ONLY on the 12v line. you can even put in a pot and have a variable supply. it will usually shut off due to overvoltage at around 14v though, unless you find and modify (or disable) the overvoltage circuit. (It probably wouldn't be a bad idea to upgrade the output caps to a higher voltage at the same time if you're running much over 12v)
The bad news as audio is concerned is that there is no good - rail to work from. they're usually just regulated with cheap 7905 7912 etc. linear regulators (hence the <1A of current)
It would probably work for a fairly low power single ended amp. (you probably couldn't get enough voltage for most designs)
It would probably work well for a class D or something meant to drive low impedance loads with very high current.
Find a cheap and popular power supply, learn to mod it, and you've got a cheap supply of high current variable bench supplies whenever you need one. 😉
It would take some fairly significant modification to get a solid -12v line out of it.
Also, it seems to be a fairly popular opinion that switching power supplies aren't good for audio. (probably accurate in most cases)
Actually, it takes some significant modification to get a solid +12v line out of them 😉
They normally regulate the + voltages from a matrix which is based on a fairly average load distribution.
for example, if you heavily load the 12V line with no load on the 5v line the 12v will usually be pulled down, and the pwm will see the voltage fall and will increase its pulse width, which will cause the 5v line to climb higher, until the matrix is at the right value.
You'll usually end up with 10v and 6.5v or something. Often there's overvoltage protection, so when one of the lines climbs too high, it'll just shut off.
I've modded supplies before for use as dc bench supplies, and they work quite well, but only once you've removed the unnecessary bits, and then changed the resistor divider so it regulates ONLY on the 12v line. you can even put in a pot and have a variable supply. it will usually shut off due to overvoltage at around 14v though, unless you find and modify (or disable) the overvoltage circuit. (It probably wouldn't be a bad idea to upgrade the output caps to a higher voltage at the same time if you're running much over 12v)
The bad news as audio is concerned is that there is no good - rail to work from. they're usually just regulated with cheap 7905 7912 etc. linear regulators (hence the <1A of current)
It would probably work for a fairly low power single ended amp. (you probably couldn't get enough voltage for most designs)
It would probably work well for a class D or something meant to drive low impedance loads with very high current.
Find a cheap and popular power supply, learn to mod it, and you've got a cheap supply of high current variable bench supplies whenever you need one. 😉
- Status
- Not open for further replies.