Audio system on a boat (12 v)

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DID

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Hi all,

I have just installed a new audio system on my boat with an outboard engine (with 4 speakers, amplifier and bluetooth reciever, as a package). Now the system works perfectly when the ignition is on (and the engine is not started; only running on the battery). But today I went out, and to my surprise, it works with a lot of outage when the engine is below 2500 rpm. When I go higher than 3000 rpm, it works flawless, so I think there might be an electrical issue. I have just coupled the Amplifier to the battery with ah 15 amp fuse (as suggested by the manufacturer).

How do I make the system work even at idle speed/rpm?

Thanks
 
Welcome to ETO!
Can you monitor the audio supply voltage when the engine is below 2500rpm, and again when above 3000rpm?
 
Thanks, Yes, i have a multimeter, but where exactly should I measure, on the battery poles? The voltage gauge is always between 13.5-14 volt when the engine is running, but it seems like that its not getting enough when the RPMs are low...
 
alec_t said:
As close as possible to the actual + and - inputs of the audio device (amplifier, whatever).
Click to expand...
OK, thanks I will do that.

If the voltage coming to the unit is to low, what are my options to increase that? Should i re-wire the ground?

And I am also wondering, why is the system working perfectly with the ingnition on (i.e. from the battery alone), and not when the engine is on... I cannot understand that logic...
 
Are you sure that the problem is not interference from the engine affecting the Bluetooth link. Can you dry it with the audio source connected directly to the amplifier as a way to prove it is related to the Bluetooth link ? You could also try powering it from a separate battery to see if the problem still occurs.


Les.
 
Could the engine really do that? I dont know much about BT technology, but I thought it was some sort of protected from interference. I have however noticed, that when I "jiggle" with the BT antenna on the amplifier (its sort of a lose 15 cm wire) then there might be an improvement, but I neglected it thinking it was a coincidence..

Thanks
 
DID said:
Could the engine really do that? I dont know much about BT technology, but I thought it was some sort of protected from interference.
Click to expand...

Nothing is 'protected' from interference, it 'might' have a little built-in resistance to it - but only against low levels of interference. Digital TV for instance includes extra bits for 'error correction', and the quality reading on your TV is an indication of how much error correction is taking place - the higher the value, the less correction is been used. But it can only go so far, once it gets too bad the entire system collapses - which is why you get the 'digital cliff' on Digital TV reception.
 
DID said:
Could the engine really do that?
Click to expand...

Ignition systems are notoriously noisy.

Many cars have earth straps to the bonnet to protect the car's radio systems from the ignition noise.

Just about all outboard motors are petrol engines with spark plugs, so I am assuming that is what you have. The engine covers are plastic or fibre glass so do next to nothing to shield any electrical noise.
 

And while cars have considerable suppression (as they commonly have radios in them) a boat engine may be less so.
 
If the battery is charging from an alternator on the engine, that may also be causing a voltage ripple and upsetting things.

Higher engine revs means higher ripple frequency, so more easily reduced or eliminated by normal PSU smoothing & filtering circuits.
 
DID said:
Should i re-wire the ground?
Click to expand...
Depends how it's already wired. The radio/amplifier ground should be wired direct to the battery; not to a wire which is carrying ignition coil or other engine-related heavy current.
 
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