Hiya, I'm worried about the 'boom' when i turn on my Naim NAP150 amp (maybe upstream in the pre-amp etc, ) and whether it will damage my speakers. I decided to build a speaker protection board for my speakers but all of the ones i can find on ebay etc join together the two -ve sides of the speakers together and switch the +ve.
My question; looking at the NAP 150 PCB it looks like the -ve of the speakers is routed separately and i'm worried that linking them externally might be a bad idea.
Has anyone added external protection before?
Given how old the Amp is i might have opened it up and added a delayed 2PDT relay but it's still sounding amazing and is still worth money so i don't want to destroy it completely - conversely i don't want it wrecking my speakers either.
My question; looking at the NAP 150 PCB it looks like the -ve of the speakers is routed separately and i'm worried that linking them externally might be a bad idea.
Has anyone added external protection before?
Given how old the Amp is i might have opened it up and added a delayed 2PDT relay but it's still sounding amazing and is still worth money so i don't want to destroy it completely - conversely i don't want it wrecking my speakers either.
The PCB seems to take a round-about way to link them together - guessing to maintain the star earth.. I wonder if i'm about to create a nice earth loop through my speaker protection circuit?
I don't think an external relay won't work, you can use two single channel speaker protection board separate the negative post on both channels.
https://www.amazon.co.uk/Speaker-Protection-AC10-18V-DC12-24V-System/dp/B0B7FM6M7J
Or you can find some NE555 0-10 second delays on relay module, replace the relay with a better one like an Omron G2R, and you're good to go.
That is an interesting observation. If I’m reading this correctly, the aftermarket protection boards have joined the speaker negative and protection board power neg (or ground) together?
I don’t believe I would do that. The sense circuit only needs a high impedance connection to the positive to detect an offset outside the SOA. The proper way to design these today is to keep the protect board’s power supply and neg/ground isolated from the pos and neg speaker terminals, especially in this age of balanced outputs and class D. Sometimes the speaker neg isn’t really a ground.
So i've reached a working prototype solution that i'm not happy with:
As you can see i've followed the pattern of linking the -ve side of the speakers together. Lesson from response above is to plan ahead and install 2 x protection boards and more importantly 2 x power supplies as they would link the -ve too if there were only one. Now onto building my production model with nice wiring. Decided against just a timed relay as these modules offered DC offset protection as well as soft-start.
As you can see i've followed the pattern of linking the -ve side of the speakers together. Lesson from response above is to plan ahead and install 2 x protection boards and more importantly 2 x power supplies as they would link the -ve too if there were only one. Now onto building my production model with nice wiring. Decided against just a timed relay as these modules offered DC offset protection as well as soft-start.