I have not been on the forum for quite a while and I expected to find the definitive amplifier protection circuit had been developed and accepted as the ultimate circuit but my search did not discover such. Is there a circuit that is, more or less, considered the best for high power DC output amplifiers?
Not everyone agrees on the solution. There are several ways to do each part of it, and some people will even argue that protection circuits "degrade the sound".
Short circuit / over current protection is where the biggest disagreements seem to be. Some people like traditional VI limiters, but others say they can introduce distortion. Others like to implement an over-current trip, where the speaker relay opens if too much current passes through the emitter resistors (easy to do with a couple transistors). Speaker fuses are still pretty common for MOSFET amplifiers.
And we can't even decide on the relays themselves. People can argue all day about which mechanical relay they like best, and some people like to use SSRs / MOSFETs in this and apparently have good results in doing so.
If you have +/- 15V available in your amplifier, op-amps make the DC protection really easy. With one or two transistors and an op-amp, it's easy enough to do over-current trip protection too.
The one thing I don't understand is why some people believe that protection circuits are optional. Even the best amps can fail, and the last thing you want is for it to take $6,000 worth of speakers with it. Furthermore, the power rails in many solid-state amps are high enough to give a pretty nasty shock, so DC protection is, IMO, mandatory.
Short circuit / over current protection is where the biggest disagreements seem to be. Some people like traditional VI limiters, but others say they can introduce distortion. Others like to implement an over-current trip, where the speaker relay opens if too much current passes through the emitter resistors (easy to do with a couple transistors). Speaker fuses are still pretty common for MOSFET amplifiers.
And we can't even decide on the relays themselves. People can argue all day about which mechanical relay they like best, and some people like to use SSRs / MOSFETs in this and apparently have good results in doing so.
If you have +/- 15V available in your amplifier, op-amps make the DC protection really easy. With one or two transistors and an op-amp, it's easy enough to do over-current trip protection too.
The one thing I don't understand is why some people believe that protection circuits are optional. Even the best amps can fail, and the last thing you want is for it to take $6,000 worth of speakers with it. Furthermore, the power rails in many solid-state amps are high enough to give a pretty nasty shock, so DC protection is, IMO, mandatory.
Agree, never you can know when a power transistor will fail. 😱
I will never connect main speaker without protection to any amplifier!
Use cheap speaker for test when a protection isn't available. 😉
Another option is a large electrolytic in series with the hot line.
I will never connect main speaker without protection to any amplifier!
Use cheap speaker for test when a protection isn't available. 😉
Another option is a large electrolytic in series with the hot line.
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Yes, I was hoping that someone had come up with a better solution than a few years ago and is not more complicated than the amplifier itself. Looks like I am stuck with a more traditional approach for my amps.
Thanks for responding.
Thanks for responding.
I have designed a few protection circuits.
I am from a PIC microcontroller background so tend to use those.
I have used 4 second anti thump delay, DC protect, mains failure detect and over current detect.
I am from a PIC microcontroller background so tend to use those.
I have used 4 second anti thump delay, DC protect, mains failure detect and over current detect.