Power Amplifier Output Protection

kosalev · 16th November 2007, 09:48 AM

Hi all!

Could enybody please discribe me the pros and cons of two types of output protection in a high-power amplifier? we can protect the loudspeakers with output relays and we can electronically close/mute the output transistors without relays. Wich one is better and why?

Regards:
Levente

AndrewT · 16th November 2007, 10:43 AM

Hi,
the relay is a slow acting device and usually used to prevent long term overheating damage. eg to prevent a heatsink getting too hot or to prevent a voice coil from burning out.

The electronic limiting can be made to be very fast and this is more suitable for protecting the semiconductor devices from damage.

Neither is better or worse, they do different jobs.

I advise that you add fusing to that protection list. A mains fuse feeding the amplifier and supply rail fuses between the main PSU smoothing capacitors and the amplifier PCB.

All these protection systems must be designed to allow all normal audio signals to pass without alteration to all normal loads. That is the difficult bit.

kosalev · 16th November 2007, 11:39 AM

Thanks Andrew!

16th November 2007, 09:48 AM	#1
kosalev diyAudio Member Join Date: May 2007	Power Amplifier Output Protection Hi all! Could enybody please discribe me the pros and cons of two types of output protection in a high-power amplifier? we can protect the loudspeakers with output relays and we can electronically close/mute the output transistors without relays. Wich one is better and why? Regards: Levente

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16th November 2007, 10:43 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, the relay is a slow acting device and usually used to prevent long term overheating damage. eg to prevent a heatsink getting too hot or to prevent a voice coil from burning out. The electronic limiting can be made to be very fast and this is more suitable for protecting the semiconductor devices from damage. Neither is better or worse, they do different jobs. I advise that you add fusing to that protection list. A mains fuse feeding the amplifier and supply rail fuses between the main PSU smoothing capacitors and the amplifier PCB. All these protection systems must be designed to allow all normal audio signals to pass without alteration to all normal loads. That is the difficult bit.

16th November 2007, 11:39 AM	#3
kosalev diyAudio Member Join Date: May 2007	Thanks Andrew!