I have the 1237 in my amp, tested and works as intended. I replace the cheapo relays it came with though, with Potter & Brumfield ones for the sake of overkill.
Very versatile regarding optional functions as well.
http://ampslab.com/PDF/upc1237.pdf
It seems like there are two types of speaker protection kits at ebay. One is using the UPC1237, which is a dedicated speaker protection IC, and the other circuits is just using transistors and some other basic componentes.
Here are the links:
UPC1237 Speaker Protection IC Datasheet
Speaker Protection Without UPC1237
Speaker Protection With UPC1237
Offtopic:
I've been using this forum for a while, basically just for reading. Still there are one thing at this forum that I truly don't understand; How in the world can a single forum post have 200+ pages (!!)? Many of these posts are many years old! It really makes is hard to read the whole post (If you have the same probles as the post describes) because several members "hijacks" the thread, and taking it in a new direction.
Can someone please tell me why this is done on this forum, but never on other forums?
IMO that's far better than having hundreds of threads about the same thing, at least all the answers are grouped together.
BTL is bridging...two amplifiers are operated 180 degrees (out of phase) and the load connected to the two outputs...this increases the voltage swing to the load.
Paralleling is when two (or more) amplifiers are operated with the same output signal on all outputs and then those are connected together...This increases current capability.
If parallel bridging is a combination of the two then you will need an even number of chips...as previously noted.
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Back on the speaker protection topic...
If I were to use speaker protection I would first institute a soldered in fuse or a pcb fuse holder...not an inline fuse holder.
The next level I would use would be DC detection and the opening of a very good relay.
As suggested by Arty, capacitors can be used for DC protection.
If I were to use speaker protection I would first institute a soldered in fuse or a pcb fuse holder...not an inline fuse holder.
The next level I would use would be DC detection and the opening of a very good relay.
As suggested by Arty, capacitors can be used for DC protection.
Dug,
I have actually heard a tweeter being fried by an amplifier dying with a high frequency yawl. Only once, and it was a while ago, but I seem to remember that both were taken out. The capacitor won't do much for that.
Nor will the suggestion that I'm about to make, either. But it might save an amp going through its death throes. I'm very pro regulation and having some control over power supplies. Normally I'd go with some sort of current limiter, and hope that would do. It could certainly protect the power transistors (but that may not be the point we are after). Nor is a bit of DC for a short time going to do harm - and could even be a consequence of just an asymmetry in the waveforms.
One really needs a way of assessing power. This isn't ideal as a first suggestion, but it could be refined. You basically charge up a discharging capacitor and, if it hits a threshold of voltage (comparable to the power limits of the speaker or even your output stage), you throw a relay open. And it only gets reset by a restart. This allows peaks of current, that if they are not of sufficient duration have no energy content, then it gets ignored; but you don't have the sag in voltage that a current limiter has, which would have squashed that peak. (And current limited distortion is possibly as bad as it gets.) I don't know that it's beyond the DIY community to implement that (I'm ashamed to say I have hardly thought about how to do it) but it can't be that difficult. At the worst one would end up using a comparator, but that's hardly difficult.
You just have an NC relay, that ought to weld itself together with corrosion because it never gets used, which one day gets forced open, but saves the amp and the speakers from the children!
I have actually heard a tweeter being fried by an amplifier dying with a high frequency yawl. Only once, and it was a while ago, but I seem to remember that both were taken out. The capacitor won't do much for that.
Nor will the suggestion that I'm about to make, either. But it might save an amp going through its death throes. I'm very pro regulation and having some control over power supplies. Normally I'd go with some sort of current limiter, and hope that would do. It could certainly protect the power transistors (but that may not be the point we are after). Nor is a bit of DC for a short time going to do harm - and could even be a consequence of just an asymmetry in the waveforms.
One really needs a way of assessing power. This isn't ideal as a first suggestion, but it could be refined. You basically charge up a discharging capacitor and, if it hits a threshold of voltage (comparable to the power limits of the speaker or even your output stage), you throw a relay open. And it only gets reset by a restart. This allows peaks of current, that if they are not of sufficient duration have no energy content, then it gets ignored; but you don't have the sag in voltage that a current limiter has, which would have squashed that peak. (And current limited distortion is possibly as bad as it gets.) I don't know that it's beyond the DIY community to implement that (I'm ashamed to say I have hardly thought about how to do it) but it can't be that difficult. At the worst one would end up using a comparator, but that's hardly difficult.
You just have an NC relay, that ought to weld itself together with corrosion because it never gets used, which one day gets forced open, but saves the amp and the speakers from the children!
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Why not just build a robust amp in the first place rather than a cheapie gainclone.
If you don't want relay contacts in series with your valuable signal why not go for the crowbar approach. Use whatever detection you like but use that to short out the power supply instead of having it in series with the signal. You can short the PSU with an SCR and use that that to blow the PSU fuse in the event of failure.
If you don't want relay contacts in series with your valuable signal why not go for the crowbar approach. Use whatever detection you like but use that to short out the power supply instead of having it in series with the signal. You can short the PSU with an SCR and use that that to blow the PSU fuse in the event of failure.
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What do you mean by that?
Every amp benefits from protections the same way.
Aham.. Sure.
At least some chip amps have built in protections.
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Are all Chip Amps cheapie? In principle they are no worse than most. (And some might resent the implication.
)The crowbar approach doesn't work unless you have heavy engineering behind it. It certainly won't run if you have a regulated supply and your choice is blowing one set of transistors or the other. Or maybe both.
It's also terribly inelegant. Not just for its reliance that a fuse will blow before a transistor (which is usually unlikely) but for the principle of relying on huge masses of copper windings as your backup. It's almost 19th Century in its principle.
I have to say I have never liked it - not even in 1975 when I was first told about it. Sure, then it would save your house burning down, so was useful in that respect. But do you not agree that it's a cludge, clunky, solution.
LM3886 does not need short circuit protection, it is adequately protected internally, to some there is too much protection. It uses a mechanism to limit dissipation in the output stage. It is sensitive to overvoltage, reverse voltage and output to rail short, but seems to be very tolerant of output shorts (output to ground) and immune to BTL shorts (two outputs from two chips shorted together).
About speakers, I have used many of these chips over the years (I have more than 20 of them in my house in different avatars) and none of them has destroyed a speaker - I only have lost about 5 chips so far in 10 years, which were caused by carelessness and rail-to-output short or reversed power supplies. In no case has the speaker suffered damage. The power supply and current involved do not seem to be enough to do any lasting damage, but to be safe if you have sensitive and delicate speakers you may want a protection circuit.
It would seem from your application that it is not required.
About speakers, I have used many of these chips over the years (I have more than 20 of them in my house in different avatars) and none of them has destroyed a speaker - I only have lost about 5 chips so far in 10 years, which were caused by carelessness and rail-to-output short or reversed power supplies. In no case has the speaker suffered damage. The power supply and current involved do not seem to be enough to do any lasting damage, but to be safe if you have sensitive and delicate speakers you may want a protection circuit.
It would seem from your application that it is not required.
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