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#1
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Help! Continuing to blow out my amplifier
Greetings,
I am continuing to blow out my "whole house" amp and neither my audio installers nor I can figure out what the problem is. And I am tired of paying these jokers $100 per hour to not fix the problem that they caused in the first place! I do not know if it is a short somewhere or the load is just too much. The Scenario 1) I am an electrical novice... so I kind of get that speakers have resistance and I once knew what that meant. 2) I have 9 pairs of speakers hooked to some kind of resistance device so far back in the component cabinet that I cannot tell you what brand it is... but I can tell you it is set to "10" at the point where it asks "number of speaker pairs". The other choices are "8,6,4, and 2". I have tried both 8 and 10 with the same ultimate result. 3) The speakers are eiether in ceiling speakers or outdoor speakers. All by paradigm (I believe). I do not know what the ohm-age ratings are. 4) Mostly there each connector on the resistance thingy has only one pair of speakers but in the case of two of the connectors there is two pairs of speakers hanging off each in series. 5) each set of speakers has its own in wall volume control. 6) The amplifier driving these is a Rotel RB-981. (http://www.rotel.com/products/pdfs/rb981.pdf) With, I believe, 2x130 Watts of power. 7) I am playing continuous music from a PC running musicmatch through a marantz receiver that is then sending its second zone out through the rotel. I do not believe the source is relevant... but let me know if you want more details. 8) The Rotel lasts about 30 days and seems to be working fine then it blows. I have tried opening it and replacing the fuses but they blow almost immediately once it goes. It has been back to Rotel 3 times! The Questions This is driving me to distraction. What can I use to test each speaker for shorts? What can I do to test the speaker switcher? What is the math I need to do to determine whether I, in fact, have too high of a load? Thanks a ton for your help... I'll send a boomerang out to anyone who gives me some good clues. Dave |
#2
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Help! Continuing to blow out my amplifier
It sounds like the amplifier is under rated and not designed for what you
want to do, and the impedance loading is not right. For these applications there are power amplifiers specially designed to take multiple speaker loads. Also, normally a 70 Volt speaker system is put in with an amplifier designed to run 70 Volt speaker systems. Each speaker box would have a 70 Volt to 8 ohm transformer driving it, that is rated at the required wattage for its use. Normally, we have used 50 to 100 Watt rated transformers in most installations. This gives a good headroom to avoid any possible over saturation. The amplifier you have was not designed for this type of application. The impedance loading is all over the place, because of the multiple speakers and pots. Also the total impedance is probably much too low, with a high return loss. Your amplifier will be blowing all the time! I bet if you put a standard pair of 8 ohm speaker boxes directly on it, with the proper speaker wire, the amp will run for years without failure. Look in to 70 volt audio distribution for details about how it is done, and the proper type of equipment required. check this link for an example of where to start http://www.milestech.com/mpt70.htm -- Greetings, Jerry Greenberg GLG Technologies GLG ========================================= WebPage http://www.zoom-one.com Electronics http://www.zoom-one.com/electron.htm ========================================= "dk253" wrote in message om... Greetings, I am continuing to blow out my "whole house" amp and neither my audio installers nor I can figure out what the problem is. And I am tired of paying these jokers $100 per hour to not fix the problem that they caused in the first place! I do not know if it is a short somewhere or the load is just too much. The Scenario 1) I am an electrical novice... so I kind of get that speakers have resistance and I once knew what that meant. 2) I have 9 pairs of speakers hooked to some kind of resistance device so far back in the component cabinet that I cannot tell you what brand it is... but I can tell you it is set to "10" at the point where it asks "number of speaker pairs". The other choices are "8,6,4, and 2". I have tried both 8 and 10 with the same ultimate result. 3) The speakers are eiether in ceiling speakers or outdoor speakers. All by paradigm (I believe). I do not know what the ohm-age ratings are. 4) Mostly there each connector on the resistance thingy has only one pair of speakers but in the case of two of the connectors there is two pairs of speakers hanging off each in series. 5) each set of speakers has its own in wall volume control. 6) The amplifier driving these is a Rotel RB-981. (http://www.rotel.com/products/pdfs/rb981.pdf) With, I believe, 2x130 Watts of power. 7) I am playing continuous music from a PC running musicmatch through a marantz receiver that is then sending its second zone out through the rotel. I do not believe the source is relevant... but let me know if you want more details. 8) The Rotel lasts about 30 days and seems to be working fine then it blows. I have tried opening it and replacing the fuses but they blow almost immediately once it goes. It has been back to Rotel 3 times! The Questions This is driving me to distraction. What can I use to test each speaker for shorts? What can I do to test the speaker switcher? What is the math I need to do to determine whether I, in fact, have too high of a load? Thanks a ton for your help... I'll send a boomerang out to anyone who gives me some good clues. Dave |
#3
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Help! Continuing to blow out my amplifier
(dk253) writes:
8) The Rotel lasts about 30 days and seems to be working fine then it blows. I have tried opening it and replacing the fuses but they blow almost immediately once it goes. It has been back to Rotel 3 times! Once a power transistor burns up or shorts, an overcurrent condition in the amplifier occurs. That blows the fuse. The fuse is just doing its job keeping your amplifier from burning down your home. The Questions This is driving me to distraction. What can I use to test each speaker for shorts? A VOM- volt ohm meter. Such as http://www.radioshack.com/product.as...ct%5Fid=22-223 What can I do to test the speaker switcher? What is the math I need to do to determine whether I, in fact, have too high of a load? Same piece of equipment. That meter will measure the DC resistance. The actual impedance of the speakers is slightly higher than the CD resistance. Sounds to me like the amplifier is working too hard and is "seeing" too low of an impedance. I'd also be curious about the thermal and airflow situation around that amplifier. Any amp run too hard, too hot, and for too long will eventually fail. Semiconductor device physics wouldn't have it any other way. ;-) Best Regards, -- /"\ ASCII Ribbon Campaign | Todd H \ / | http://www.toddh.net/ X Promoting good netiquette | http://triplethreatband.com/ / \ http://www.toddh.net/netiquette/ | "4 lines suffice." |
#4
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Help! Continuing to blow out my amplifier
I agree with other posters. That ROTEL would do a wonderful job if used as
designed. It sounds like this is outside of it's realm of intended use. It is not the amplifier...it's the way your speakers are wired (or lack of). the ROTEL is "seeing" a low impedance overall load (sub 4 ohms). The guys who installed didn't do a lot of thinking when designing the system. TC "dk253" wrote in message om... Greetings, I am continuing to blow out my "whole house" amp and neither my audio installers nor I can figure out what the problem is. And I am tired of paying these jokers $100 per hour to not fix the problem that they caused in the first place! I do not know if it is a short somewhere or the load is just too much. The Scenario 1) I am an electrical novice... so I kind of get that speakers have resistance and I once knew what that meant. 2) I have 9 pairs of speakers hooked to some kind of resistance device so far back in the component cabinet that I cannot tell you what brand it is... but I can tell you it is set to "10" at the point where it asks "number of speaker pairs". The other choices are "8,6,4, and 2". I have tried both 8 and 10 with the same ultimate result. 3) The speakers are eiether in ceiling speakers or outdoor speakers. All by paradigm (I believe). I do not know what the ohm-age ratings are. 4) Mostly there each connector on the resistance thingy has only one pair of speakers but in the case of two of the connectors there is two pairs of speakers hanging off each in series. 5) each set of speakers has its own in wall volume control. 6) The amplifier driving these is a Rotel RB-981. (http://www.rotel.com/products/pdfs/rb981.pdf) With, I believe, 2x130 Watts of power. 7) I am playing continuous music from a PC running musicmatch through a marantz receiver that is then sending its second zone out through the rotel. I do not believe the source is relevant... but let me know if you want more details. 8) The Rotel lasts about 30 days and seems to be working fine then it blows. I have tried opening it and replacing the fuses but they blow almost immediately once it goes. It has been back to Rotel 3 times! The Questions This is driving me to distraction. What can I use to test each speaker for shorts? What can I do to test the speaker switcher? What is the math I need to do to determine whether I, in fact, have too high of a load? Thanks a ton for your help... I'll send a boomerang out to anyone who gives me some good clues. Dave |
#6
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Help! Continuing to blow out my amplifier
The other posters seem to have missed your mention of "some kind of
resistance device". This is likely a multi-tapped transformer that is designed to maintain the proper load on the amp when driving multiple pairs of speakers, such as http://www.nilesaudio.com/products/h..._matching.html. It should work fine. Make sure that they did not use shielded cable from the amp or the box, or from the box to any of the speakers. The capacitance of such cable would cause the impedance to become very low at high frequencies, which will make some amps unstable, overheat, or blow. The box may be overly capacitive. Try locating the box farther from the amp, and use longer cables between the amp and box. The inductance of the cable may then isolate the amp from the box's capacitance enough to keep it stable and working. If the "jokers" did the install and supplied the gear, it's their responsibility to make it work - free. If they don't, I'd tell them to take it away and refund your money. If they don't, take them to small claims court. (If you already had the amp and speakers, it's still their responsibility to make sure that what they add and install will function with the equipment that you supplied.) "dk253" wrote in message om... Greetings, I am continuing to blow out my "whole house" amp and neither my audio installers nor I can figure out what the problem is. And I am tired of paying these jokers $100 per hour to not fix the problem that they caused in the first place! I do not know if it is a short somewhere or the load is just too much. The Scenario 1) I am an electrical novice... so I kind of get that speakers have resistance and I once knew what that meant. 2) I have 9 pairs of speakers hooked to some kind of resistance device so far back in the component cabinet that I cannot tell you what brand it is... but I can tell you it is set to "10" at the point where it asks "number of speaker pairs". The other choices are "8,6,4, and 2". I have tried both 8 and 10 with the same ultimate result. 3) The speakers are eiether in ceiling speakers or outdoor speakers. All by paradigm (I believe). I do not know what the ohm-age ratings are. 4) Mostly there each connector on the resistance thingy has only one pair of speakers but in the case of two of the connectors there is two pairs of speakers hanging off each in series. 5) each set of speakers has its own in wall volume control. 6) The amplifier driving these is a Rotel RB-981. (http://www.rotel.com/products/pdfs/rb981.pdf) With, I believe, 2x130 Watts of power. 7) I am playing continuous music from a PC running musicmatch through a marantz receiver that is then sending its second zone out through the rotel. I do not believe the source is relevant... but let me know if you want more details. 8) The Rotel lasts about 30 days and seems to be working fine then it blows. I have tried opening it and replacing the fuses but they blow almost immediately once it goes. It has been back to Rotel 3 times! The Questions This is driving me to distraction. What can I use to test each speaker for shorts? What can I do to test the speaker switcher? What is the math I need to do to determine whether I, in fact, have too high of a load? Thanks a ton for your help... I'll send a boomerang out to anyone who gives me some good clues. Dave |
#7
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Help! Continuing to blow out my amplifier
"dk253" wrote in message
om 8) The Rotel lasts about 30 days and seems to be working fine then it blows. I have tried opening it and replacing the fuses but they blow almost immediately once it goes. It has been back to Rotel 3 times! The Questions This is driving me to distraction. What can I use to test each speaker for shorts? What can I do to test the speaker switcher? What is the math I need to do to determine whether I, in fact, have too high of a load? The Rotel is obviously a POS. A well-designed power amp will either work or shut itself down without damage, under almost any conceivable situation. Surf EBay and pick up a QSC USA 850 or 900, they usually close for about $200 (apparently the cost of just 2 hours of incompetent labor). IME the QSC will either blow away whatever is causing the problem, or it will just run indefinitely. |
#8
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Help! Continuing to blow out my amplifier
When your service guy comes in, tell him to measure the Z or wattage
consumption of the string of speakers. Those numbers have to agree with the rotel's specifications. If the guy is worth 100 per hour he should be equipped to do so and should already know what numbers he was shooting for in the first place. This procedure won't fix the system problem but it will tell you if the sound guy is a quack. This isn't rocket science. Even Radio Shack would have the answere! bg dk253 wrote in message ... Greetings, I am continuing to blow out my "whole house" amp and neither my audio big snip --------- |
#9
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Help! Continuing to blow out my amplifier
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#10
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Help! Continuing to blow out my amplifier
Thanks to everyone who responded! Very helpful.
1) I purchaed on ebay (as suggested) a QSC 850 amp for $195 2) I checked the wiring and distance and all seems ok 3) the "resistance thingy" is a russound 12 speaker set distribution panel. but I may have it set wrong. I think my amp is 4 ohm but I am not sure what the speakers are set to. I have to take one out of the cieling to find out. I do not know how to test with the ohmeter. Some more help here would be great. How would you test with the ohmmeter to see if speakers are 4 ohm or 8 ohm? Thanks Dave (dk253) wrote in message . com... Greetings, I am continuing to blow out my "whole house" amp and neither my audio installers nor I can figure out what the problem is. And I am tired of paying these jokers $100 per hour to not fix the problem that they caused in the first place! I do not know if it is a short somewhere or the load is just too much. The Scenario 1) I am an electrical novice... so I kind of get that speakers have resistance and I once knew what that meant. 2) I have 9 pairs of speakers hooked to some kind of resistance device so far back in the component cabinet that I cannot tell you what brand it is... but I can tell you it is set to "10" at the point where it asks "number of speaker pairs". The other choices are "8,6,4, and 2". I have tried both 8 and 10 with the same ultimate result. 3) The speakers are eiether in ceiling speakers or outdoor speakers. All by paradigm (I believe). I do not know what the ohm-age ratings are. 4) Mostly there each connector on the resistance thingy has only one pair of speakers but in the case of two of the connectors there is two pairs of speakers hanging off each in series. 5) each set of speakers has its own in wall volume control. 6) The amplifier driving these is a Rotel RB-981. (http://www.rotel.com/products/pdfs/rb981.pdf) With, I believe, 2x130 Watts of power. 7) I am playing continuous music from a PC running musicmatch through a marantz receiver that is then sending its second zone out through the rotel. I do not believe the source is relevant... but let me know if you want more details. 8) The Rotel lasts about 30 days and seems to be working fine then it blows. I have tried opening it and replacing the fuses but they blow almost immediately once it goes. It has been back to Rotel 3 times! The Questions This is driving me to distraction. What can I use to test each speaker for shorts? What can I do to test the speaker switcher? What is the math I need to do to determine whether I, in fact, have too high of a load? Thanks a ton for your help... I'll send a boomerang out to anyone who gives me some good clues. Dave |
#11
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Help! Continuing to blow out my amplifier
"dk253" wrote in message
m I do not know how to test with the ohmmeter. Some more help here would be great. How would you test with the ohmmeter to see if speakers are 4 ohm or 8 ohm? Connect the ohm meter across the terminals of the speakers(s) you want to test. The reading on the ohm meter is very close to the speaker's nominal impedance. Yup, that simple! It should be between 1 ohm and 20 ohms. If it's less than 4 ohms, it's too low. |
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