dietermoreno
- Dec 30, 2012
- 238
- Joined
- Dec 30, 2012
- Messages
- 238
Why did my PA fuse blow?
Note: this thread has NOTHING to do with radios or radio building, and if I start going off topic about that please lock the thread and ban me again.
Okay, so I have a PA amplified speaker that my friends were using to play music from my laptop while singing over it.
Unfortunately, the microphone was having feedback at high volume of the music from the laptop.
The music from the laptop connects to the PA with an RCA red and white unbalanced and unshielded stereo audio line.
The mic connects to the PA with an XLR balanced mic line for use with a Shure SM-48 caridoid dynamic mic.
The PA is 500 watts. The PA has 3 channels (mono unbalanced audio line ins) and one RCA red and white stereo audio line in. The third channel is shared by the RCA line in.
The mic is connected to channel 1. The laptop audio interface is connect to RCA line in, which is channel 3.
The vocalist is facing the opposite way that the speaker cone is facing. The speaker is about 15 feet away from the vocalist. The mic pickup is really good and his voice can be picked up by the mic even when he is holding the mic 2 feet away from his mouth (this might be a bad thing for where feedback is concerned).
When we turned up the volume on everything up to 80%, the fuse on the PA blew.
The fuse was 3.15 amps.
I bought a replacement 3 amp fuse from the local hardware store and it blew as soon as I plugged in the PA into mains outlet even with the gain on all channels turned to zero!
So I think that 3 amps is no good and I need exactly 3.15 amps or it won't work. So I think I will need to order the exact current amount (3.15 amps) fuse on Amazon or else it won't work.
So I didn't order the fuse yet on Amazon but I will soon. I actually think I'll wait a few days for advice from you guys before I waste $0.10 and then $5 shipping if I'm doing something wrong.
So why did the fuse blow the first time with the gain not all the way up?
Why did the fuse blow the second time with a replacement fuse only .15 amp off as soon as I plugged it into mains even with all channels gain set to zero?
Is it possible that regenerative principles from the feedback of the mic could have caused the fuse to blow the first time with the gain not all the way up?
by regenerative principles, I mean the feedback when tickled with its own input (the unshielded unbalanced RCA line could have tickled it maybe), the output is greatly increased, and the output could be increased greater than the amount of current that the circuit is designed to handle.
Would using a balanced stereo line to transmit the music from the PC audio interface to the PA help at all to remove the feedback?
Note: this thread has NOTHING to do with radios or radio building, and if I start going off topic about that please lock the thread and ban me again.
Okay, so I have a PA amplified speaker that my friends were using to play music from my laptop while singing over it.
Unfortunately, the microphone was having feedback at high volume of the music from the laptop.
The music from the laptop connects to the PA with an RCA red and white unbalanced and unshielded stereo audio line.
The mic connects to the PA with an XLR balanced mic line for use with a Shure SM-48 caridoid dynamic mic.
The PA is 500 watts. The PA has 3 channels (mono unbalanced audio line ins) and one RCA red and white stereo audio line in. The third channel is shared by the RCA line in.
The mic is connected to channel 1. The laptop audio interface is connect to RCA line in, which is channel 3.
The vocalist is facing the opposite way that the speaker cone is facing. The speaker is about 15 feet away from the vocalist. The mic pickup is really good and his voice can be picked up by the mic even when he is holding the mic 2 feet away from his mouth (this might be a bad thing for where feedback is concerned).
When we turned up the volume on everything up to 80%, the fuse on the PA blew.
The fuse was 3.15 amps.
I bought a replacement 3 amp fuse from the local hardware store and it blew as soon as I plugged in the PA into mains outlet even with the gain on all channels turned to zero!
So I think that 3 amps is no good and I need exactly 3.15 amps or it won't work. So I think I will need to order the exact current amount (3.15 amps) fuse on Amazon or else it won't work.
So I didn't order the fuse yet on Amazon but I will soon. I actually think I'll wait a few days for advice from you guys before I waste $0.10 and then $5 shipping if I'm doing something wrong.
So why did the fuse blow the first time with the gain not all the way up?
Why did the fuse blow the second time with a replacement fuse only .15 amp off as soon as I plugged it into mains even with all channels gain set to zero?
Is it possible that regenerative principles from the feedback of the mic could have caused the fuse to blow the first time with the gain not all the way up?
by regenerative principles, I mean the feedback when tickled with its own input (the unshielded unbalanced RCA line could have tickled it maybe), the output is greatly increased, and the output could be increased greater than the amount of current that the circuit is designed to handle.
Would using a balanced stereo line to transmit the music from the PC audio interface to the PA help at all to remove the feedback?
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