periodic chirp (or squeak?) every ~12 seconds

[jmacinnes]

Hi all,
I'm trying to track down the source of this regular, periodic low-pitched chirp (the best I can describe it is like the sound of a small, tight zipper being zipped up really fast).

• it's very regular, always about 12s in between chirps. Each chirp is short, say 250-500ms.
• it's loud enough to be irritating, but not affected by adjusting the volume pot
• predominantly in the left-channel; present, but fainter in the right
• successive chirps are always about the same loudness, but somedays it is louder than others.
• it's present when unplugging the RCA inputs, so it's not coming from the DAC or computer.

This is a Crack w/ Speedball, and I'm listening through Sennheiser HD650's. I first checked all of the voltages, and reflowed any joints that looked suspect. I'm now wondering if it could be something in the outlet or interference from something else. I confirmed the outlet was grounded, but not sure what to test next.

Has anyone heard of a similar issue before? Or any ideas about where to look next? Thanks!

[Paul Birkeland]

This is likely interference from something close by that's a wireless device (phone, router, etc).

[jmacinnes]

Thanks, Paul! I just turned the wi-fi and bluetooth off on my phone, ipad, and laptop, and moved them all downstairs to a far room, but still getting the chirps. The router is downstairs as well, beneath the room the Crack is in. Later this afternoon I'll try to shut the router down and see if that changes things.

[mcandmar]

Do you have a UPS or other battery based backup system anywhere in the house?     I have heard them produce a noise like that, specifically APC units. I think its something to do with the battery charge circuit giving a pulse at a fixed interval.  Very annoying if you have one in your office, once you hear it you cannot un hear it.

[jmacinnes]

Removing all devices and shutting off the router downstairs didn't make a difference. I moved the crack to different outlets around the house, and the chirp occurs on any outlet connected to the original circuit, but not other circuits. These outlets are all in the same region of the house, so I suppose that doesn't rule out interference in the area from some other device, but I'm hard pressed to think what that might be. To test whether its interference or something in the circuit, maybe I can try plugging an extension cord into the original outlet and running it to an area of the house where there's an outlet that the crack doesn't chirp at, and testing it there.

No UPS on this circuit (or anywhere else that I know of), mcandmar, but your suggestion of a battery backup system gave me hope it might be coming from the wired smoke detector in the room. But alas, removing it from the circuit didn't do anything.

[Deke609]

What else do you have plugged into or powered by that same line?  You can figure that out by flipping the breaker that controls that outlet and checking to see what else is turned off.

cheers, Derek

[Paul Birkeland]

Try turning your phone all the way off.

[watonwak]

It sounds exactly like interference from my phone when its connecting via mobile data. When i enable WIFI calling on my phone it goes away.

[jmacinnes]

Still no luck tracking this down, but more evidence that it's interference and not coming from the outlet/circuit.

• I shut down all phones, computers, tablets, and unplugged or took the batteries out of any "smart" device throughout the house. Unplugged everything else on that circuit (just a few lamps, and a turntable, receiver, and tuner, all of which haven't been on during other tests). Still chirping.
• Chirps seem dependent on location. It chirps when keeping the amp in the same location, but powering off of different house circuits. Conversely, there are location near outlets on other circuits in the house where it doesn't chirp, and if I run an extension cord from the original outlet to this location, still no chirps.
• I walked out a rough grid on the floor of the office where I'm set up, and the chirps are definitely louder near the outside wall of the house. It varies in intensity at different locations, but not in any other sort of pattern that I could figure out.

For what it's worth, my home office is on the 2nd floor of a 100+ y.o. house in a relatively dense neighborhood (Phinney/Greenwood in Seattle, for anyone who knows it). Powerlines maybe 40' out the window, and a neighbors house ~20'. Pigeons right outside the window, but they don't appear to be radio collared. I don't know, stabbing in the dark here about what the source of interference might be.

I'm on a mission to figure this out now. But I guess the more practical question is: is there anything I can do about it (short of moving my office to a different part of the house)? Is there anyway to shield the amp, somehow?

[oguinn]

Try this

https://forum.bottlehead.com/index.php?topic=11676.0

[jmacinnes]

Thanks for the tip! Looks easy enough. I'll order those diodes and give it a shot and report back.

[jmacinnes]

Shoot, sorry to say that adding the ground breaker mod didn't have any effect on the chirps. For 11 seconds I was really hopeful.

Assuming the amp is picking up interference, what kind of combination of signal strength and distance from the amp could produce this sort of effect? My sense was that interference from a device like a computer or phone would have to be reasonably close to the amp, but after shutting down devices throughout the whole house I'm still racking my head over what the source could be.

[Deluk]

Do you have battery powered smoke alarms that have an auto self test circuit? Have you tested the Crack in another house or location?

[jmacinnes]

There is a set of 5 wired-in smoke detectors with battery backups throughout the house, but I disconnected them all to test, and still chirping. There are locations around the house where I can move the crack to and not hear the chirps.
I should also mention that this is a new phenomenon that started once I moved into this new place. Previously, I've had the crack for ~2 years in a different house with no issue. The crack's new room is set up almost exactly the same as the old room in terms of placement relative to laptop and stereo receiver, etc.

[Paul Birkeland]

The knowledge that other places in the house remove the chirps is helpful.  It may be that you need to swap the circuit branch that feeds where you plug in the Crack to the other half of the breaker box.  Still, if you're in a single family home, you should be able to shut stuff off and eventually find what's polluting the line.  You may find that shutting off one breaker at a time on your panel may be what it takes to figure out where the polluting device is connected.