Slope demodulation requires something in the (RF part of the) system to have a bandwidth similar to the FM deviation. Very unlikely in an accidental receiver.simon7000 said:
When I first started in amateur radio I used a few watts of AM on 144MHz. I quickly discovered that I was coming out loud and clear in my neighbour's record player. I switched to FM. No problem. Audio systems do not demodulate FM, except in the very rare condition that something in the system is resonating at or near the carrier frequency.
No, there's no 70v line dist in our system.
The test with the DSP box OFF indicated no pops at all while the DSP was off. We're trying to scare up a good line filter next. After the holidays.
Thanks again to everybody that's posted thoughts!
The test with the DSP box OFF indicated no pops at all while the DSP was off. We're trying to scare up a good line filter next. After the holidays.
Thanks again to everybody that's posted thoughts!
It is surely a dry solder problem on old equipment. Put ON only the amp and wait to listen for the pops, and ...
Gajanan Phadte
Gajanan Phadte
it does seem that the DSP is the source of the popping(reminds my of a similar experience with an SPX 90 that developed a supply problem) if the supply filters of the DSP are going(which seems a possibility) i don't think a line filter will help.
Thanks again for the ideas. We've had the pops ever since the "new" system was installed, so it's not "old equipment", nor is it filters "going". Whatever is bad was bad from new. Since we don't want to be without any PA, we need to explore the line filter before sending the DSP in for service....
I suggest a UPS as they have filtering and contact the service center. They should be able to send you an advance replacement.
If the mic inputs on the DSP have the phantom power activated that could be the source of the random pops.
Phantom power on a cable, connector, connected piece of equipment can cause strange problems if there is any issues with what is connected.
With the DSP/mixer you have the only way to turn the phantom power off (if it is on) is to connect it to a computer with the biamp software and go in that way.
With the DSP on disconnect the inputs one at a time and see if that narrows down the problem.
Phantom power on a cable, connector, connected piece of equipment can cause strange problems if there is any issues with what is connected.
With the DSP/mixer you have the only way to turn the phantom power off (if it is on) is to connect it to a computer with the biamp software and go in that way.
With the DSP on disconnect the inputs one at a time and see if that narrows down the problem.
Random static pops, to me, sound like there is a clock issue. Whenever there is dsp and digital signal transfer involved, a clock keeps everything "talking" in sync. When there is a mismatch between two clocks (ie 44.1 vs 48) or improperly assigned master and slave devices (ie 2 masters) this kind of sound manifests. Check your clock settings to make sure that if you have just one digital device that it is the master and clocking itself. If you have multiple digital devices, say remote preamp modules feeding the mixer, that there is only one master and EVERYTHING else connected to it is clocked by it.
Mike, we get pops even with all inputs disconnected.
W0J0, all the inputs are analog, as are the outputs. We get the pops even if we disconnect all of the inputs. The only clock is within the DSP system.
W0J0, all the inputs are analog, as are the outputs. We get the pops even if we disconnect all of the inputs. The only clock is within the DSP system.
It could also be some loose wire/connection on the mains, a thermostat, and so on...
Gajanan Phadte
Gajanan Phadte
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Would you please draw a diagram showing the placement of the equipment.
Are the amps in the same location as the signal boxes?
Is the amp plugged into the same outlet?
jn
Are the amps in the same location as the signal boxes?
Is the amp plugged into the same outlet?
jn
I'm not really good with diagrams, but . .
All the PA hardware is in a small rack. Wireless receivers on top, then DSP, then two-channel amplifier, then power sequencer/line filter. The rack is at the very back of the sanctuary. There are several mic cables that are run to the front, but I don't believe that we have anything happening on these runs, as we get the pops even when all inputs are disconnected at the DSP.
I did some measuring of resistance between the various grounds, and found that they all seem to be well connected to each other (less than 1 ohm from anything that appeared to be ground to any other).
We did get a consultant involved over the holidays, and he's thinking that we may need to "float" the grounds. That test is pending.
All the PA hardware is in a small rack. Wireless receivers on top, then DSP, then two-channel amplifier, then power sequencer/line filter. The rack is at the very back of the sanctuary. There are several mic cables that are run to the front, but I don't believe that we have anything happening on these runs, as we get the pops even when all inputs are disconnected at the DSP.
I did some measuring of resistance between the various grounds, and found that they all seem to be well connected to each other (less than 1 ohm from anything that appeared to be ground to any other).
We did get a consultant involved over the holidays, and he's thinking that we may need to "float" the grounds. That test is pending.
Hi,
I fixed a power amp ,I found a loud intermittent pop when it got warmed up ,The power supply capacitors had lugs on them for connectors that were pressed aluminum just like a rivet,at no certain times it would pop through the speakers,I did find black oxidation around the rivet,which suggest a loose connection,If you have a scope put it across your speaker outputs and wait for it to pop,or giggle some wires especially around the power supply, or hit the amp cabinet with a screw driver handle to cause some vibration, how old are the amps? Capacitors,especially the big ones in power supplies can start going bad after 5 years,and sometime sooner depends on quality and amount of heat exposure,also look for loose connections,especially spade connectors,
Hopes this helps,
NS
I fixed a power amp ,I found a loud intermittent pop when it got warmed up ,The power supply capacitors had lugs on them for connectors that were pressed aluminum just like a rivet,at no certain times it would pop through the speakers,I did find black oxidation around the rivet,which suggest a loose connection,If you have a scope put it across your speaker outputs and wait for it to pop,or giggle some wires especially around the power supply, or hit the amp cabinet with a screw driver handle to cause some vibration, how old are the amps? Capacitors,especially the big ones in power supplies can start going bad after 5 years,and sometime sooner depends on quality and amount of heat exposure,also look for loose connections,especially spade connectors,
Hopes this helps,
NS
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NoSmoking, thanks for the thought. Not our issue, I replaced the amp, and it made no difference. Last weekend, though, I "floated" the ground from the wall plug. We had no pops at all Sunday. It was raining, so that may be the reason for no pops, so we'll continue testing...
Well, today we had pops. Floating the ground didn't fix it. No rain today, pops. Back to diagnosis.
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