Speaker switching on 4 ch class D Amp

[Captn Dave]

This post poses a question about speaker switching on a multi channel class D amp.

Background. I have a little solar powered travel trailer with a POS amp within the otherwise okay factory head. It has indoor and outdoor speakers. I can get a nice small class d 4 channel power amp and use the stereo rca pre outs as input. All is well with all four speakers going. But I’ll want to switch the speakers so I don’t freak out the bears and the chuckwallas.

Now, I can either switch the pre amp input signal (A, B, or both) OR switch the ground on the speakers, thus running a pair of channels of the amp with no load. Since I’m being real stingy with power consumption, I want to do it in a manner that is most power efficient.

What is the best way to do this?

 

[DUG]

What class D chip is used?

Some designs do not like no load conditions...signal or not...Some tend to get broken and the smoke gets out.

The best way might be to disconnect power to the channels that you don't want on.

 

[Think]

Why not use 2 stereo boards?

 

[Captn Dave]

I originally intended to use two stereo boards but I came into a great deal on a commercial 4 channel car amp that will fit into the tiny space available. I’m going to try and use it. When a channel isn’t in use I may need to switch from speakers to load resistors if the no load condition is an issue for this amp.

 

[nigelwright7557]

With no speaker load a class d amp's output filter will start to ring at high volts and possibly fry something.
In fact with a irs2092 design it sometimes stops oscillating with no load and the output sits at +17VDC.

 

[Think]

I don't really seem to get what your idea is; but switching the speakers is probably not the best solution.
You have a stereo headunit with double (A/B) line out? Just connect each channel to a channel on the amp and use the A/B switch. Powering the amp with no input signal on 2 of the 4 channels, but with load (speakers) is no problem.

 

[Captn Dave]

I didn’t mention that I have but one set of RCA outputs. I ended up splitting and switching the input signal so as to avoid running the output without load as several of you had cautioned against. It works well.

Thanks for the help.