protection in amps is a very good thing but many dont like them ...... but neways i recently designed a 500W @ 8E amp which is going for the PA use so i would like to use a shortcircuit protection for my amp ...... All u learned people can u help me with this...... Cause a PA amp does nt need to have very good sonics just average sonics with heavy protection is needed.... The protection scheme can be very simple ....
regards
phoenix
regards
phoenix
shuting down in PA bussiness Andrew, is unaxeptable or impossible to happen some time you will have to understand this
everything you do has to happen before amplifier fails or shut down the cost of shuting down will be by far more than a few transistors and some fuse
I have been the audience.
I know it's unacceptable to shut down.
But there is a point where the protection will prevent the bad signal passing or a good signal passing to a bad load. That time period must be short. During that time of shutdown, the redundancy in the sound system must cover up the shortfall.
If you cannot hide the shutdown then the audience complains.
I know it's unacceptable to shut down.
But there is a point where the protection will prevent the bad signal passing or a good signal passing to a bad load. That time period must be short. During that time of shutdown, the redundancy in the sound system must cover up the shortfall.
If you cannot hide the shutdown then the audience complains.
protection ciruit in performance
Sakis, hopefully, for an amp with protection circuits in a performance venue, the speaker shorts and wiring faults are found by the protection circuit in the sound check, and the amplifier shuts down then, leaving the road crew to find the faults with a meter and get everything back running before the actual performance.
I find the cavalier discussion of safe area limiters on custom microprocessors a bit humorous, toys of rich boys. The only way I could afford a VI limiter I know is to buy a blown up Crown or similar professional amp and repair the blown up parts, assuming the microprocessor is not the blown up part. The last catelogs I have, microprocessor development systems are $4000, the emulator umbilacle accessory was $1500, the software development package was $2000. This was for Intel equipment. HP logic analyzers are about $4500. Factory ProgrammableLogicController's are much cheaper in the $300 range but with their 1 bit interface they don't take measurements very well. If you know something better, please spill it.
Until microprocessor development becomes knowable and affordable, the rest of us will have to make do with DC blocking caps in the speaker lines, timer controlled and thermistor controlled speaker relays, speaker fuses, diac-triac speaker shorting assemblies that usually detect blown output transistors, similar second rate solutions. If you look at what someone7272 found, Rapid Electronics - Electrical & Power a packaged protection circuit, I wonder if this is snake oil or if there is some way to communicate amp power on state and VI data to this device. I tried the specifications link on that website and came up with a screen with a tiny logo on it, so I am leaning towards it might be snake oil.
Sakis, hopefully, for an amp with protection circuits in a performance venue, the speaker shorts and wiring faults are found by the protection circuit in the sound check, and the amplifier shuts down then, leaving the road crew to find the faults with a meter and get everything back running before the actual performance.
I find the cavalier discussion of safe area limiters on custom microprocessors a bit humorous, toys of rich boys. The only way I could afford a VI limiter I know is to buy a blown up Crown or similar professional amp and repair the blown up parts, assuming the microprocessor is not the blown up part. The last catelogs I have, microprocessor development systems are $4000, the emulator umbilacle accessory was $1500, the software development package was $2000. This was for Intel equipment. HP logic analyzers are about $4500. Factory ProgrammableLogicController's are much cheaper in the $300 range but with their 1 bit interface they don't take measurements very well. If you know something better, please spill it.
Until microprocessor development becomes knowable and affordable, the rest of us will have to make do with DC blocking caps in the speaker lines, timer controlled and thermistor controlled speaker relays, speaker fuses, diac-triac speaker shorting assemblies that usually detect blown output transistors, similar second rate solutions. If you look at what someone7272 found, Rapid Electronics - Electrical & Power a packaged protection circuit, I wonder if this is snake oil or if there is some way to communicate amp power on state and VI data to this device. I tried the specifications link on that website and came up with a screen with a tiny logo on it, so I am leaning towards it might be snake oil.
yet again the same issues the same problems and the same story on trying to make people from a diferent school to understand .....
Indianajo :
I agree to 1000% to what you say the real problem remains very simple .... you need a good machine? then overdesign everything .... big coolers many transitors big supply and so on ....this is not cost effective ....
you need lower cost effective equipment ??? use VI limmiters LDR and all the rest .... OK but they kill your sonics ....
ok then what is the available ways ???
VI limmiters or multislope vi limmiters Ldr protection or combination of both
since for normal class AB ams it seems there is no other way then the trick is to optimize this as much is possible and wait till something more inovative comes arround
only a few days ago i come across a mosfet amplifier that has no VI limmiter only gate stoppers with zeners and so on but has some kind of monitoring on the VAS curent ... i dont know how well it works but someway that is something new at least to me ...
it will be so wonderfull as you say to use Mp monitor voltage and current in all stages of the amplifier and tune all voltage on line and in real time but sounds like space technology to me
the point remains the same good sonics and vi limmiters don go together ....then again pro amps and no VI limmiters also dont go together
so what is the solution ???
Indianajo :
I agree to 1000% to what you say the real problem remains very simple .... you need a good machine? then overdesign everything .... big coolers many transitors big supply and so on ....this is not cost effective ....
you need lower cost effective equipment ??? use VI limmiters LDR and all the rest .... OK but they kill your sonics ....
ok then what is the available ways ???
VI limmiters or multislope vi limmiters Ldr protection or combination of both
since for normal class AB ams it seems there is no other way then the trick is to optimize this as much is possible and wait till something more inovative comes arround
only a few days ago i come across a mosfet amplifier that has no VI limmiter only gate stoppers with zeners and so on but has some kind of monitoring on the VAS curent ... i dont know how well it works but someway that is something new at least to me ...
it will be so wonderfull as you say to use Mp monitor voltage and current in all stages of the amplifier and tune all voltage on line and in real time but sounds like space technology to me
the point remains the same good sonics and vi limmiters don go together ....then again pro amps and no VI limmiters also dont go together
so what is the solution ???
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Current sense
A current sense circuit, Included in the amplifier section. that Triggers the Protection circuit, to disconnect the loudspeaker for two seconds.
Warning the user of the low load.
In my case I can adjust it to disconnect the speaker for 2 seconds or 3 seconds. at
4 ohms
OR
2 ohms
Thanks
A current sense circuit, Included in the amplifier section. that Triggers the Protection circuit, to disconnect the loudspeaker for two seconds.
Warning the user of the low load.
In my case I can adjust it to disconnect the speaker for 2 seconds or 3 seconds. at
4 ohms
OR
2 ohms
Thanks
in small PA setup with two or three amps ...this is never supposed to happen then again the stress you are going to produce in relays psu and clamp diodes with a quick click at full power is way too much trouble and it can create more drouble than it can solve
What i meant also in my previous post everybody things that the amplifier is untouchable and everything you do happens after the amplifier ....the idea and solutions needed BEFORE OR MUCH BEFORE the relay clicks or the vi limmiter has been eating all your sonics
What i meant also in my previous post everybody things that the amplifier is untouchable and everything you do happens after the amplifier ....the idea and solutions needed BEFORE OR MUCH BEFORE the relay clicks or the vi limmiter has been eating all your sonics
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i have a idea in mind ...... How bout putting a sensing resistance in series with the load may be (0.1E) then take two connections from the end of the resistor and feed it to a differential amp and then feed the o/p of the diif amp to a comparator which in turn drives a relay .......
As soon as a high current pass through the sensing resistor a voltage drop will be there which will amplified using the diff amp then the diff amp will drive the comparator and and the comparator will activate a relay which will disconnect the load and the amp will be protected....... Suggestions if this concept will work ......
regards
aniket
As soon as a high current pass through the sensing resistor a voltage drop will be there which will amplified using the diff amp then the diff amp will drive the comparator and and the comparator will activate a relay which will disconnect the load and the amp will be protected....... Suggestions if this concept will work ......
regards
aniket
I can see what you are thinking but I'm afraid it won't work.You are showing the speaker across the 12 volt supply.
You can sense current using a low value resistor (but you need to be able to sense both polarities... an amp can fail either way.
Sensing like this relies on a large current in the sense resistor (up to the max output of the amp) before the circuit trips... and there is no integrating of the audio either... the slightest peak over the set level would activate it.
For DC offset it's no good as the current to trip it is as stated way to high... the speaker would be toast
Good thinking though
ok my bad here is the corrected schematic ... I already have a dc detect protection circuit from rangy slones book & a turn on delay ............ I also have a temperature based fan speed regulator from rod elliot ..... Neways the sensing resistor is in series with load so why should nt detect the negative part of the signal...... Correct me if I am wrong
circuit
regards
aniket
circuit
regards
aniket
Attachments
Hi Phoenix,
Your idea could work with a bit of refinement. Firstly you do not want to reference your circuit to the amplifier ground, it should be "floating" like your Multi meter. Secondly you may want to add a full wave bridge so that you can monitor negative and positive faults, and thirdly you may want to add an integrator as Mooly suggests so that you don't cut the speakers for any peak, but only those that say lasts for more than 1 second.
Finally I do not think it should reset automatically but should latch so that you need user intervention to check what went wrong and maybe have to turn the amp on and off for it to reset.
On the whole this is not a bad idea for protecting your speakers for fault currents which is the most damaging to speakers.
I guess some of the purists would argue that you are messing with the damping factor by incorporating a series resistance, but for a protection circuit this is a fine idea. Try refining your idea and post it as a complete add on board, I am sure there are many here that could make use of it.
Kind regards
Nico
Your idea could work with a bit of refinement. Firstly you do not want to reference your circuit to the amplifier ground, it should be "floating" like your Multi meter. Secondly you may want to add a full wave bridge so that you can monitor negative and positive faults, and thirdly you may want to add an integrator as Mooly suggests so that you don't cut the speakers for any peak, but only those that say lasts for more than 1 second.
Finally I do not think it should reset automatically but should latch so that you need user intervention to check what went wrong and maybe have to turn the amp on and off for it to reset.
On the whole this is not a bad idea for protecting your speakers for fault currents which is the most damaging to speakers.
I guess some of the purists would argue that you are messing with the damping factor by incorporating a series resistance, but for a protection circuit this is a fine idea. Try refining your idea and post it as a complete add on board, I am sure there are many here that could make use of it.
Kind regards
Nico
Here's the schematic of an "AF Drive Indicator" that was published in Elektor in the early '90s. The article includes a PC board layout. LEDs indicate clipping and 3 dB below clipping.
AF Drive Indicator Schematic
If anyone is interested, let me know and I'll scan the original article.
AF Drive Indicator Schematic
If anyone is interested, let me know and I'll scan the original article.
Wow thats a lot of components.
I can do a clip led with 5 small cheap components including the LED !
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