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Pop through speakers when furnace starts/shuts down

Bradbrews said:
Years ago I built a small fan that ran on 120 volts to cool my NAD amp. It had a relay that was thermostat controlled to turn it on and off. When I first tried it out there was a great pop noise that came through the speakers when it turned off. It happened even when the unit was powered with an extension cord from a remote output. The amp was picking up the signal generated by the relay contacts opening over the air. It was acting like a radio receiver and amplifying the signal as if it was part of the audio it was supposed to amplify.
I added a small ceramic cap across the relay and the pop was completely eliminated.
You may have a similar situation.
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This sounds like EXACTLY what is happening here! I’m going to request my HVAC guy do this to see if it cures the issue.
 
I will say that the Tripp Lite Isobar surge suppressor and power conditioner does make a noticeable change to the sound quality. The music just sounds cleaner, clearer and more accurate. Perhaps a bit more bass even. It just doesn’t prevent the pops/cracks.

Like the comment above, I think the thermostat signal from the relay contacts is being amplified.
 
Is the breaker for the furnace and the breaker for your Marantz on the same side of the breaker box? If so try using an extension cord and power the Marantz from an outlet powered by a breaker on the opposite side of the breaker box and see if it improves the situation. If it does perhaps you could move that circuit to the other side of the breaker box. Both the breaker and the wire coming off the breaker would have to be moved.
 
If the Pop is being picked up from airborne transmission from an arc, maybe you just need to find and remove the antenna. One possible spot for this could be the pre out main in jumpers. A quick check would be to replace them with shielded RCA cables. It’s a bit of a long shot but it’s easy.
If it’s happening when playing LPs those long wires in the tonearm might be the antenna. Not much you can do about that however.
 
Replaced thermostat with one with solid state switching. No change, still pops. Furnace completely off, hot water heater completely off, refrigerator unplugged, still pops. So can rule out the furnace as the cause at this point

It has to be coming from the receiver. Within minutes of powering it on, I get the loud crack. Almost like a capacitor is loading up and dumping voltage? DC coming from somewhere?

I started a new thread in the Marantz area as well to see if someone else might have gone through this and has a suggestion.

lots of time, money and still no change or fix!
 
Bradbrews said:
Years ago I built a small fan that ran on 120 volts to cool my NAD amp. It had a relay that was thermostat controlled to turn it on and off. When I first tried it out there was a great pop noise that came through the speakers when it turned off. It happened even when the unit was powered with an extension cord from a remote output. The amp was picking up the signal generated by the relay contacts opening over the air. It was acting like a radio receiver and amplifying the signal as if it was part of the audio it was supposed to amplify.
I added a small ceramic cap across the relay and the pop was completely eliminated.
You may have a similar situation.
Click to expand...
I suspect that what you have described is the problem in this case, which is why I suggested in post #3
rothwellaudio said:
The pop could be due to a spike in the mains voltage or it could be due to a burst of RFI caused by the furnace switch arcing. If it is RFI you could could try suppressing the noise at source (a snubber on the switch) or try an RF filter on the amp's input.
Click to expand...
If the problem is indeed a burst of RF noise being transmitted by an arcing switch no amount of mains filtering will cure it because the noise isn't coming through the mains wiring.
 
yellowwagon said:
Replaced thermostat with one with solid state switching. No change, still pops.
Click to expand...
Is the solid state switching actually turning the furnace on and off, or just triggering a relay?
yellowwagon said:
It has to be coming from the receiver. Within minutes of powering it on, I get the loud crack. Almost like a capacitor is loading up and dumping voltage? DC coming from somewhere?
Click to expand...
I thought you were convinced the crack coincided with the furnace switch. Are you now saying it just happens randomly?
 
Up until today, the receiver didn’t pop with the furnace switched off (coincidence). However, with the furnace switched off today as well as all other electrical devices in my house, the receiver still popped. The receiver was the only thing “on” and it popped.

The popping wasn’t happening every time until recently now it seems to be happening more regularly. Turn on the receiver, it plays music beautifully for a few minutes and then “CRACK.”

believe me, I thought I had it narrowed down to the furnace or the thermostat being the cause. That isn’t the case now since I’ve gotten the receiver to pop without the furnace operating.

I have since started a thread in the Marantz forums since this issue continues and isn’t related to the furnace like I thought.
 
rothwellaudio said:
I suspect that what you have described is the problem in this case, which is why I suggested in post #3

If the problem is indeed a burst of RF noise being transmitted by an arcing switch no amount of mains filtering will cure it because the noise isn't coming through the mains wiring.
Click to expand...
rothwellaudio said:
I suspect that what you have described is the problem in this case, which is why I suggested in post #3

If the problem is indeed a burst of RF noise being transmitted by an arcing switch no amount of mains filtering will cure it because the noise isn't coming through the mains wiring.
Click to expand...


Not RF noise from the furnace or thermostat
 
yellowwagon said:
It is dry this time of year. Humidity level is 40% inside the house
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Unplug all the cables, reinstall, might find something with an issue. Hell, as it's a receiver, unplug everything and just use the radio, this should rule out any outside equipment connected and associated cables.

If it still persists change the speakers, if still run an extension cord to another room, if still give it to someone to try at their house. If the issue still persists............well you have your answer.
 
Doubt this is the issue but when I first bought my house whenever the A/C would turn on the streetlight would dim. I had the service upgraded to 200 amps. Eventually I lost electricity to half my house. I called the power company and they found that where the wires connect from the pole to the weatherhead were cheap aluminum lugs. It had corroded causing a large voltage drop. It didn’t cause any issues with my sound system though. Maybe something to check if all else fails.
 
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