Amp help

[MrD]

I picked up a car amp to use in my jukebox.   It has a trimode where:

"Simultaneous stereo/mono opeation. Tri-Mode requires the use of passive crossovers to send low frequencies to the mono subwoofer speaker and higher frequencies to the stereo speakers.  Tri-mode is used when you have a single amplifier and you want to run a complete speaker system - front satellite speakers and rear subwoofer."

Then it lists a table and a wiring diagram to use inductors and capacitors.  The wiring I understand.  But the chart shows 3 columns, the HZ, the inductor and the capacitor.

100hz, Inductor 6.35mH, Capacitor 400 uF
120hz, Inductor 5.3mH,  Capacitor 330uF
etc.

Does this mean that if I want to cut off everything below 120hz to the stereo speakers, I use 5.3mH, and 330uF?  Anything below 120hz would go to the subwoofer?   

I think that's what it means anyway.   The amp is 55 watts per channel RMS or 140 watts bridged for the subwoofer.   I'm thinking I'll use some coaxial speakers for the satellites and then use a single bridged subwoofer.

I jsut want to know if I'm on the right track.  Thanks

[richms]

Thats not really a feature of the amp, its something you can do on any bridgable amplifier, you are basically building 3 passive crossovers.

That would be the correct way to choose the components, but at the end of it you may not be able to get the levels matched properly since the chances of you having similar efficiancies on the small speakers and the sub are pretty remote.

[MrD]

All that I posted is straight from the amp manual.  It is a brdigeable amp.  It says it can do this "tri-mode" thing.  It's the table that confused me.  The Hz and inductors/capacitors.  I think I'm right that it is the cut off frequency (over and under)  Probably worth a shot for me to try it out.  Worst case I'll do a second amp for the subwoofer.

[digitaldj]

As i have mentioned in another post i don't like running the amp from a computer power supply. The reason is the computer power supply is a switching supply and not a constant current supply that is supposed to be used for audio amps.

Just as a suggestion, it is always better to biamp when your are including a sub woofer into the system. You will always want to control the sub volume unless you use a Lpad which is a volume control circuit that keeps the correct impedance.

The best system always is a seperate amp for Highs, Mids, lows and sub but it is way to expensive. The alternative to that is Lpads and one amp. Always use crossovers if you want the best sound possible and the crossovers have to be matched to the speakers frequency range.

Kevin

[richms]

A car amp is fine off noisy power - after all it works in a car, it has an internal DC-DC converter that will remove most of the noise in the supply.

You may end up with it creating a ground loop back via the soundcards shield which is in close proximity to the other IO chips if its onboard. I would guess thats a more likly souce for the noise then the power to the amp, and since they are both unbalanced theres not a lot you can do other then to try one of the line level isolators from a car audio shop, but in all the cases I have tried those they have added other problems due to lousy shilelding of them,.