Amp on - no input or speaker?

[si_blakely]

I have 2x150W Mosfet amps (Maplin kitsets). They have seperate power supplies, but a single Stereo Speaker Protection/Dethump circuit. The main use for this will be driving one or two 12" bins as personal stage monitors.

The question is, when this is running mono, can the unused amp channel be powered up with no input/output, or should I switch power to each channel seperately. I would rather not do this, as my bass playing 14yo daughter will be the prime user and I do not want to stress her too much by having too many don'ts.

Of course, the other option is to have two mono amps, but that means building a second Speaker Protection circuit (and another case etc).

Any thoughts

Si

 

[Tekko]

Paralell the channels, double power and no risc that a unhooped channel can break.

 

[djQUAN]

I think connecting the unused input to ground via a 1k resistor would keep the amp stable.

if you would like to make it useable, use two separate gain controls for each channel, turn the unused channel to min and don't worry about it. works for the amps I have built.

 

[si_blakely]

and fry my bins which will not handle 300W

Si

 

[Brion55]

Most pro sound amp mfgs use switched input jacks that short the input to ground when it's not in use.

Like this:

 

[si_blakely]

How would that be implemented - just a pot across the amp inputs?

Si

 

[Frank Berry]

"Paralell the channels, double power and no risc that a unhooped channel can break."

I suggest that you DO NOT ever do this. Paralleling the outputs can damage the amplifier.

I've never had a problem with using only one channel of a two channel amplifier. If you're really worried about damage to the idle amplifier, insert a plug into the input with the tip shorted to ground.

 

[si_blakely]

Thanks guys - I'll change the inputs from RCA to switched jacks.

Si

 

[anatech]

Hi si_blakely,
To be honest, don't worry about it. An unloaded channel will not cause any trouble unless it's a tube amp (transformer output). So don't change anything. Frank Berry has made a good point & I agree totally.

-Chris