stealing power supply from sub-amp

[skogs]

Hi, Im just about to build a rumble filter for my subwoofer. And it would really ease things up if i could use the excisting preamp power supply inside my present sub-amp, a zachry dsw-250.
Im a little nervous about starting to fiddle inside my amp without knowing exactly what im looking for.
so, could anyone give me any pointers for how i can find the -V, +V and GND i need?

thanks

[richie00boy]

A volt meter would be a good start

[skogs]

yeah thanks, actually i didnt think about that:P

any other clues i might follow? do you think that the things i need can be found in wires, or is it maybe somewhere on a pcb?

[richie00boy]

You just need to find the main ground, then find the +15 and -15 wires or points/tracks to tap into.

[skogs]

Yes, but how do i know which wires, points or tracks are the right ones? do you think it will easily be spotted?

[richie00boy]

Ground should be reasonably logical if you trace things like where the PSU caps are commoned and the speaker returns to. Maybe you can guess where the 15 volt wires are too by tracing to another board if there is one. Then check with the volt meter using the black probe on the ground point.

[skogs]

thanks for the guidelines ill try to find it. but can i use any of the grounds from anywhere on the amp? even the black wire leading to the speaker?

[richie00boy]

No that speaker ground would be the worst one to use because it will be full of heavy dirty currents.

You should choose your ground carefully, likewise try and choose somewhere clean and sensible to pick off your 15 volt points.

[DoomPixie]

if there are any op amps in that amp then you can find the +/- voltages there.. and ground is usually fairly easy to find..
Owen