Re: Sound!
Posted: Wed May 24, 2017 7:28 pm
Yep, check if the speaker is open circuit (after disconnecting it from the amp). It should read a few ohms, around 60% of it's rated impedance, say 5-6 ohms for a nominal 8 ohm speaker.
If it is open circuit the lash-up may have made the amp oscillate at an ultrasonic frequency frying the speaker. Why use a 60W amp on such a small speaker? I suggest using a simple analogue amp, not a class D amp, of just a watt or two. Without any filtering on the output of the PWM and that applied to the speaker could have fried it too. Use a filter and a simple analogue amp is all I can suggest, say a LM386 to get you going, a few hundred milliwatts. I've never had a problem with this method.
A few hundred milliwatts is more than yer average laptop shoves into its speakers.
Steve A.
The TPA3118 also has a BTL output arrangement (Bridged Transformer-Less) i.e. the speaker must be connected to the terminals marked 'Output', not connected to ground/0V anywhere. This is how the high output powers at low supply voltages are generated.
As an aside, class D amps generate a lot of HF noise much the same as switched-mode power supplies as they conceptually use the same method. Quite frankly I wouldn't go anywhere near them.
If it is open circuit the lash-up may have made the amp oscillate at an ultrasonic frequency frying the speaker. Why use a 60W amp on such a small speaker? I suggest using a simple analogue amp, not a class D amp, of just a watt or two. Without any filtering on the output of the PWM and that applied to the speaker could have fried it too. Use a filter and a simple analogue amp is all I can suggest, say a LM386 to get you going, a few hundred milliwatts. I've never had a problem with this method.
A few hundred milliwatts is more than yer average laptop shoves into its speakers.
Steve A.
The TPA3118 also has a BTL output arrangement (Bridged Transformer-Less) i.e. the speaker must be connected to the terminals marked 'Output', not connected to ground/0V anywhere. This is how the high output powers at low supply voltages are generated.
As an aside, class D amps generate a lot of HF noise much the same as switched-mode power supplies as they conceptually use the same method. Quite frankly I wouldn't go anywhere near them.