# +12 and -12

#### Overclocked2300

Joined Apr 24, 2005
124
Well do we all now the 24V Trick on computer powersupplies? If not you just use the 12V lead as your positive and the -12V lead as ground, and some how you get 24V ( I assume its kerchoffs law)

So My question is, if the 2 sides provide a different amount of current, which side will supply it?

Example

+12=10Amps
-12=1Amps

And my load consumes 4 Amps total. Does it take current from the -12V side first, and then take the rest of the current from the +12V side?

#### Brandon

Joined Dec 14, 2004
306
Originally posted by Overclocked2300@Sep 12 2005, 02:40 PM
Well do we all now the 24V Trick on computer powersupplies? If not you just use the 12V lead as your positive and the -12V lead as ground, and some how you get 24V ( I assume its kerchoffs law)

So My question is, if the 2 sides provide a different amount of current, which side will supply it?

Example

+12=10Amps
-12=1Amps

And my load consumes 4 Amps total. Does it take current from the -12V side first, and then take the rest of the current from the +12V side?
[post=10288]Quoted post[/post]​
Thats fine to get 24v that way.

I'm going to take a crack at it and figure it would depend on the lesser of the 2 currents. Since one can supply all it wants, but if the other can't sink it, it doesn't matter, or vice versa. If this is incorrent, please correct me.

Current doesn't get taken from one side then the other, it always flows in 1 direction with DC currents, which you have in a PC powersupply. In basic circuits class you will learn that electrons comes from the + first. Then in advanced physics you will find it actaully comes from the negative terminal, then in EM Fields/Wave you learn electrons move so slow in wire it would take 10 mins for a light to turn on if the electrons supplied the power, so its not the electrons at all, but now the charge the electrons can transmit.... sorry you asked yet?

#### Overclocked2300

Joined Apr 24, 2005
124
Yea electrons flow from Neg to Pos, or was it current flows from neg to pos..?

EDIT: While were on the subject, Im be getting this kit soon:http://store.qkits.com/moreinfo.cfm/fk671

It requires 25 to 35V at 2 amps per side. I Am wondering if a 25 VCT 8 amps Transformer will be enough (since its class AB Ive read something about requiring alot of current when the audio signal peaks)

And let me get this otehr thing correct, its 2,500uf Per amp required Correct? So I would need 10,000uf per side Correct? (I used 4 amps instead of 8).

or would a 20VCT 4A transformer be enough?

#### mozikluv

Joined Jan 22, 2004
1,435
Originally posted by Overclocked2300@Sep 12 2005, 10:07 PM
Yea electrons flow from Neg to Pos, or was it current flows from neg to pos..?

EDIT: While were on the subject, Im be getting this kit soon:http://store.qkits.com/moreinfo.cfm/fk671

It requires 25 to 35V at 2 amps per side. I Am wondering if a 25 VCT 8 amps Transformer will be enough (since its class AB Ive read something about requiring alot of current when the audio signal peaks)

And let me get this otehr thing correct, its 2,500uf Per amp required Correct? So I would need 10,000uf per side Correct? (I used 4 amps instead of 8).

or would a 20VCT 4A transformer be enough?
[post=10303]Quoted post[/post]​

hi

use the 25v CT 8 amps. as to your caps a 2000uf/amp will suffice but use the 8 amps rating not the four. a 20v CT 4A will sag down to about 18v once the low & very low bass goes blasting.

moz

#### Overclocked2300

Joined Apr 24, 2005
124
The 4 amps I was talking about was 4 amps perside. Since the amp requires 2 amps and the peak the transformer can supply is 8, I designated 4 amps per side.

#### Yeti

Joined Jul 26, 2005
35
Hello,
Interesting kit. I have a 12" ~4ohm subwoofer sitting around. I would love to be able to build an amp for it and a box and use it for my computer.
How, from the data given from the link, can i determine if the amp can handle a 4ohm load or an 8ohm load?

Also for this subwoofer, i dont know the power rating. They usually go by the impedance of the woofer(typically 1,2,4 ,or 8 ohms) #of voice coils, power handling(ie. 100Wrms)....
How can i determine this subwoofers power handling?

I am almost certain the sub could handle 48Wrms, but its best not to assume. Would this kit be the best for the application i want to do?

Thanks
Yeti

#### Overclocked2300

Joined Apr 24, 2005
124
Considering its a 12Inch..It has to handle atleast 100W+ Or so. Is there a model number on it? If so google it.

With an input sensitivity of 1 Vrms with an impedance of 100 Kohms, and an output power of 48W RMS class AB in 4 or 8 Ohm load.
It says 48W into 8 ohms or 4 ohms, but usualy more power is delivered into a smaller resistance.

1ohm speakers are meant to handle 1KW+ of power. 2 Ohms= about the same, 4 and 8 ohms anywhere from 50W to 500W.

#### mozikluv

Joined Jan 22, 2004
1,435
Originally posted by Overclocked2300@Sep 15 2005, 01:57 PM
The 4 amps I was talking about was 4 amps perside. Since the amp requires 2 amps and the peak the transformer can supply is 8, I designated 4 amps per side.
[post=10359]Quoted post[/post]​
hello,

if that's the case, then it will suffice for the amp need.