Tripping on speaker wires is pretty common in bar band setups, and not unheard of in home environments. I've done it and pulled the speaker wire out, fortunately on a tube amp where it didn't hurt anything. And there are always dogs and children. I avoided buying any amp without speaker transformer or capacitor until recently when Enzo convinced me that the Peavey CS800s, along with some similarly priced commercial amps, are self-destruction protected somewhat adequately.
In the e-bay circuit, .6 v across a .33 ohm emitter resistor is 2 amp, which is probably too much for most output transistors. Most amps use that resistance or lower. Also relays have trouble stopping huge DC currents, and those that can tend to cause problems passing low level music signals.
Peavey in the CS800x uses current transformers on the output speaker trace to detect over current at levels low enough to maybe actually protect the transistor. Their relays are not cheap and last typically 8-10 years. See the schematic diagram on eserviceinfo.com.
Michael Bean has come up with an AC current breaker that is better than relays. He has drain to drain enhancement mode NFET's in the speaker hot line, driven by photovoltaic opto isolators made by IR or Panasonic. These $8 optoisolators will develop 8 v into tiny capacitances like a NFET gate, with no power supply on the output side. Search his name for long discussions. Toshiba also makes a photovoltaic optoisolator, but it is only surface mount package. I think some of the vendors call these IC's fet drivers. I bought Panasonic APV1122 in an 8 pin dip package from Mouser. I found some 0.1 ohm 200v FETs for $1 each at newark.com.
That way the disconnect element is arc free and contact resistance constant over time. What detection you use is up to you. DC on speaker detection I am recycling from Peavey's circuit board melting triac crowbar circuit, for the PV-1.3k. Over temperature detection and over current protection are technologies I am still investigating. Any way, a flip flop (74HC74) remembers you had a problem, and I stacked a red LED on top of the APV1122 driver led for fault indication. I'm considering putting the NFETs in the supply line instead of the speaker line, to save some $5 output transistors. Takes 2 fet drivers per channel, instead of one, but same number of NFET disconnectors, I think.
In the e-bay circuit, .6 v across a .33 ohm emitter resistor is 2 amp, which is probably too much for most output transistors. Most amps use that resistance or lower. Also relays have trouble stopping huge DC currents, and those that can tend to cause problems passing low level music signals.
Peavey in the CS800x uses current transformers on the output speaker trace to detect over current at levels low enough to maybe actually protect the transistor. Their relays are not cheap and last typically 8-10 years. See the schematic diagram on eserviceinfo.com.
Michael Bean has come up with an AC current breaker that is better than relays. He has drain to drain enhancement mode NFET's in the speaker hot line, driven by photovoltaic opto isolators made by IR or Panasonic. These $8 optoisolators will develop 8 v into tiny capacitances like a NFET gate, with no power supply on the output side. Search his name for long discussions. Toshiba also makes a photovoltaic optoisolator, but it is only surface mount package. I think some of the vendors call these IC's fet drivers. I bought Panasonic APV1122 in an 8 pin dip package from Mouser. I found some 0.1 ohm 200v FETs for $1 each at newark.com.
That way the disconnect element is arc free and contact resistance constant over time. What detection you use is up to you. DC on speaker detection I am recycling from Peavey's circuit board melting triac crowbar circuit, for the PV-1.3k. Over temperature detection and over current protection are technologies I am still investigating. Any way, a flip flop (74HC74) remembers you had a problem, and I stacked a red LED on top of the APV1122 driver led for fault indication. I'm considering putting the NFETs in the supply line instead of the speaker line, to save some $5 output transistors. Takes 2 fet drivers per channel, instead of one, but same number of NFET disconnectors, I think.
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Output shortcircuit protections, and DC out can be made on alot of ways.
Here I will speak for speaker protection design:
If use triac crowbar U must use one triac able to manage couple amperes, even ten's amperes, depending of output amp power and impedance, teoretically 2 ohms amplifiers are able to deliver more RMS amps on output than a 16 Amps triac can handle; I saw couple speaker voicecoil melted, even if amp had crowbar protection circuit, the triac exploded, and rail DC goes to speaker, destroying it.
If you use relais wich disconnect speaker, also must take in mind, the DC is not AC, and if you read, on most relais says 30A/250-277Vac, and 30A/30Vdc, but less of them are able to "cut" 24Vdc in inductive circuit, even at 10 Amps, theyr contacts will generate electrical arc and melt itself.
Explained here:
AC cutting 30A relais (60Vac)
Releu in curent alternativ.MOV - YouTube
Same relais trying to cut 74Vdc (450W/4 R amp +/- supply like example)
Releu in curent(tensiune continu(a).MOV - YouTube
2 Seried contacts relais, cutting same 74Vdc
2 relee cu contactii inseriati, rupere tensiune continua - YouTube
And take advice, on those tests it was a lightbulb load, wich is resistive load, DC in inductive load (presuming voicecoil or filter inductances) seried will be more dangerous for relais contact.
And here is mine new modules with new shortcircuit output protectionfor it.
Sorry but not shared schematics, (I know, f.u.c....ing Romanian), but is a comercial product, take patience and watch movies:
https://www.youtube.com/watch?v=9m1sVXeFgck
https://www.youtube.com/watch?v=tJkwmLvt5UI
https://www.youtube.com/watch?v=Lcl-gFMOFkw
Good luck!
Here I will speak for speaker protection design:
If use triac crowbar U must use one triac able to manage couple amperes, even ten's amperes, depending of output amp power and impedance, teoretically 2 ohms amplifiers are able to deliver more RMS amps on output than a 16 Amps triac can handle; I saw couple speaker voicecoil melted, even if amp had crowbar protection circuit, the triac exploded, and rail DC goes to speaker, destroying it.
If you use relais wich disconnect speaker, also must take in mind, the DC is not AC, and if you read, on most relais says 30A/250-277Vac, and 30A/30Vdc, but less of them are able to "cut" 24Vdc in inductive circuit, even at 10 Amps, theyr contacts will generate electrical arc and melt itself.
Explained here:
AC cutting 30A relais (60Vac)
Releu in curent alternativ.MOV - YouTube
Same relais trying to cut 74Vdc (450W/4 R amp +/- supply like example)
Releu in curent(tensiune continu(a).MOV - YouTube
2 Seried contacts relais, cutting same 74Vdc
2 relee cu contactii inseriati, rupere tensiune continua - YouTube
And take advice, on those tests it was a lightbulb load, wich is resistive load, DC in inductive load (presuming voicecoil or filter inductances) seried will be more dangerous for relais contact.
And here is mine new modules with new shortcircuit output protectionfor it.
Sorry but not shared schematics, (I know, f.u.c....ing Romanian), but is a comercial product, take patience and watch movies:
https://www.youtube.com/watch?v=9m1sVXeFgck
https://www.youtube.com/watch?v=tJkwmLvt5UI
https://www.youtube.com/watch?v=Lcl-gFMOFkw
Good luck!
Both input resistors should be 100 kOhm. Can't imagine channels having different DC level protection.
From the schematic it looks like the short circuit protection should be wired to amp outputs, one to L and one to R and the other wires (the connector) to the emitter resistors L and R of both channels. I think I would not use that.
Check the input resistors for different values, please. 10 kOhm and 100 kOhm must be an error.
BTW you can use the short-circuit thing for error states of other devices or simple manual decoupling of the speakers.
BTW you can use the short-circuit thing for error states of other devices or simple manual decoupling of the speakers.
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short protect schematic
Hello
greetings any views on this short protector schematic would it work
PIN 1 connected to emitter of positive output trs
PIN2 connected to output of amplifier
PIN3 connected to emitter of negative output trs
warm regards
andrew lebon😕
Hello
greetings any views on this short protector schematic would it work
PIN 1 connected to emitter of positive output trs
PIN2 connected to output of amplifier
PIN3 connected to emitter of negative output trs
warm regards
andrew lebon😕
Attachments
POWER SUPPLY PCB
Hello
greetings trying to make power supply pcb with all protections need SHORT
CIRCUIT protection can anyone help out pcb has clip signal dc protect and thermal cut off adjustable till 125 degrees any schematics of short circuit protection will be helpful for me to try out
warm regards
andrew😉
Hello
greetings trying to make power supply pcb with all protections need SHORT
CIRCUIT protection can anyone help out pcb has clip signal dc protect and thermal cut off adjustable till 125 degrees any schematics of short circuit protection will be helpful for me to try out
warm regards
andrew😉
Attachments
90V rails .... you think a chinese relay will work here ? 🙄
Dang , just disconnect the rails entirely upon a fault condition.
2 big MOSFETS on the PS board - just as good as"pulling the plug".
OS
I use this http://www.diyaudio.com/forums/powe...ply-cap-multiplier-electronic-protection.html for my amp and it is serving me for years, ones saved my speaker.
Hello
greetings thanks for your suggestions Esperados Ultimate Protection stands out wish
all parts were available in my city so i could try it have to keep on trying
warm regards
andrew
greetings thanks for your suggestions Esperados Ultimate Protection stands out wish
all parts were available in my city so i could try it have to keep on trying
warm regards
andrew
http://www.diyaudio.com/forums/solid-state/162081-dc-servo-mosfet-amplifier-3.html
yes it WORKS has dc protection shortcircuit protection clip indicator many thanks to APEXAUDIO i feel its his best contribution to the forum wish there was a HIGH POWER
version
warm regards
ANDREW
yes it WORKS has dc protection shortcircuit protection clip indicator many thanks to APEXAUDIO i feel its his best contribution to the forum wish there was a HIGH POWER
version
warm regards
ANDREW
Thank you for reply. Interesting approach. 2*42V AC too much for me. Had you figured out which components should be adjusted according to your transformer? I have 2*26V AC for example.
Edit: Answered in thread:
http://www.diyaudio.com/forums/soli...post2441191.html?highlight=6k8/1W#post2441191
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As Ockham said many hundred years ago, the simplest solution is (almost) always the best. There is this one dollar IC (TA 7317)readily available anywhere that proved to be best, most efficient protection in my practice. Its drawback is that the short circuit protection works only if emitter (or source) resistors are employed in the OP stage. Also in some cases you need a one transistor/channel circuit to activate the short circuit protection. Otherwise it is extremely simple, reliable,fast, works on wide supply voltage range, equipped with DC protection that trips the relay above 1 V DC on the outputs. You can find dozens of application examples on Google for various output stages, power range, also commonly used in lots of commercial designs.
Hello dragonweed
greetings can you post some short circuit schematics for amplifiers having emitter resistances using ic TA7317
WARM REGARDS
Andrew
greetings can you post some short circuit schematics for amplifiers having emitter resistances using ic TA7317
WARM REGARDS
Andrew