Don't get me started on cucumber sandwiches. I have not seen one of those since I left school and only then in the teachers common room. I have however been to many cricket matches and I can tell you that beer and BBQ are what are consumed there.
I remember that joke from a radio comedy show in the late 1940's. It was about a robe or maybe a cloths line.
Another:
What do you do if you need a robe with only one end?
You take a normal rope and just cut one end off.
Gents,
When the protection scheme invokes, how long does it take for it to recover?
The tigersaurus example I posted a while ago uses simple transistors to clamp the drive to the outputs, but they have nothing in place to stop them from saturating during the effort. So if for example, I drive a large bass line into a Watt, and some midrange content invokes the foldback, how long will it take for the clamp transistors to come out of saturation? How does modern protection prevent that?
John
When the protection scheme invokes, how long does it take for it to recover?
The tigersaurus example I posted a while ago uses simple transistors to clamp the drive to the outputs, but they have nothing in place to stop them from saturating during the effort. So if for example, I drive a large bass line into a Watt, and some midrange content invokes the foldback, how long will it take for the clamp transistors to come out of saturation? How does modern protection prevent that?
John
Sorry, we don't use that kind of amp protection anymore. It is usually too invasive and limits the sound quality. Almost any sort of E-I protection limits the amp severely. We worked years on this problem. The best way around it is more sophisticated sensors and perhaps total temporary shutdown of the amp or disconnection from the loudspeaker with a relay.
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No reason to be sorry..😀
When I played mobile, the best thing was instantaneous clamping, shutdowns of any kind are not good for the crowd despite the fact that they were "inebriated".. I had to worry about the tweeters on my own dime..
However, I suspect that each designer considers it in their own way. You mentioned using enough silicon that SOA could never be violated..I like that the best...but practically, I would think most designers will still use clamping with some hard/soft scheme.
Hey, what'd ya think about that silver on silver graph I tossed your way? When I saw that data I recalled your statements from years ago and knew you'd like it...
John
Like we already know from experience, silver on silver contacts are one of the best sounding. The CTC Blowtorch only used these sort of contacts when possible.
Bob Cordell also discusses SOA wrt the OPS and concludes similarly that it is problematic. I think the right way is to use additional output pairs if you after top quality. If the load gets really nasty, disconnect it - modern trench mosfets offer single digit Rds(on) and disconnect times of 100-200 us with less than optimal drive.
More and better output devices are much better than E-I limiting. It spreads the heat to the heatsink better as well.
Amen to that! In fact, I find that making more efficient use of the heat sinks is what I need much more than V-I limiting, at least at home and with associated power levels. (for very loud, window pane rattling I peak at about 70W).
You can almost make an amp indestructible by adding power transistors, but what about protecting speakers? What if the speakers cost more than the amp?
Shouldn't that be the job of the speaker designer? He knows best what his product can take and what it cannot, so let him build in fuses or whatever to protect it and take his share of responsability.
The loudspeaker designer should only protect his tweeters. Fuses are really bad for quality reproduction. Real amp designers protect speakers as best they can by looking for DC offset, too much clipping, oscillation, and any unnatural problem. We get sued when speakers fail.
The speaker designer can put crowbar protection inside the speaker. But before engaging the protection, the speaker must detect if the amp is more expensive than the speaker or not...
Use fuse wire for speakercable 😉
Joke aside, amps should have protection circuits for DC, massive Clipping and HF- Ringing at the outputs.
I prefer more power on the amp than the speaker can do, so no clipping and no killed Tweeters. Overload on woofers is normally audible , thus turn volume down an its ok.
With active speakers thermals sensors on TW make sense.
Joke aside, amps should have protection circuits for DC, massive Clipping and HF- Ringing at the outputs.
I prefer more power on the amp than the speaker can do, so no clipping and no killed Tweeters. Overload on woofers is normally audible , thus turn volume down an its ok.
With active speakers thermals sensors on TW make sense.
You don't need to get anywhere near the clipping point to have your tweeter die on you. If there's an leak in the supersonic region (as from CD players or MC phomo RIAA satges) which reaches the power amp output terminals, you'll soon find you tweeters dead as a doornail with say 1/3 if the nominal power output. Just as you may find your woofer trying to get out of the cabinet and hit you with tray subsonic FM signals, as I did and cured the problem by engaging the subsonic filter.
Thta's my point, John. If you have taken reasonable steps to protect the amp frpm the dpeaker and vice versa, why shoud the speaker desigber be absoved from all of his sins?
I protect the amp from foreseeable problems, like excess DC, overheating, etc, and I even have a LED status panel showing that the channels are live (green LED), their nominal 0 dB levels (orange LED) and their +2 dB over nominal points (high L red LED). If someone chooses not to pay attention to warning lights, how is that my fault? I gave him the ability to keep a reasonable check on ouput power. But America may well be a world case of litigation culture. Read about an old lady who decided to dry her doggie in the microwave, the doggie disintegrated and she sued because nowhere in tha manual was any mention of NOT putting dogs in microwaves. She was awarded just under $1 million. Everywhere else on the planet, the law is satisfied once you write down that no live matter should ever be put in a microwave and that disregarding this warning could end in a serious health hazard, including possible death.
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