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Stacking DC Blockers?

jonfitch

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In my bedroom my amplifier keeps shutting down. I've tried 6 different receivers (of different models and brands) and they all have this problem. Basically after idling for about 3-4 hours or so, they go into protection mode and shut down randomly. Sometimes this happens during playback, but most of the time this happens while just idling. I tried using an Emotiva CMX-2 but I'm not sure how much it's helped--it's eliminated any toiroidal amp hum I previously had, but I still get random shutdowns, so I think it's reduced most of the DC offset but not all of it. The receivers are all sitting out in the open and room temperature is quite low so its not a thermal issue.

I'm thinking of maybe getting another DC offset blocker and connecting it to the CMX-2 before connecting to the receiver. I'm wondering would that actually improve the DC offset blocking ability by stacking DC blocking devices, or is it like sunglasses where you actually get less UV protection when you stack them (or even make no difference)?
 
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jonfitch

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Yeah I don't have shutdown issues with these amps in other rooms. I have a computer and some laptops and a TV in my bedroom and none of these devices have ever experienced shutdowns either, it only happens with receivers. Powered speakers aren't affected either, I have a pair of Audioengine speakers that I keep on sometimes 24 hours a day and it's never had any issues. I've used a pair of Genelecs in here and they've never shut down, even on most of the day.

Something is causing A/V receivers to go into protection mode randomly in this room, and I've tested them on 4 different sockets and they all have this issue, either directly plugged into the socket, or using a generic power strip or the Emotiva CMX-2. I figured it was a DC offset issue because I get amp hum if I don't use the CMX-2.
 

GXAlan

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I don’t know but the CMX2 seems to have a limit to its DC blocking. I don’t have audible hum so my baseline DC is pretty low. Since you have audible hum from your transformer and the CMX2 fixed it, it may be worthwhile to try a second one…

 

solderdude

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Yeah I don't have shutdown issues with these amps in other rooms. I have a computer and some laptops and a TV in my bedroom and none of these devices have ever experienced shutdowns either, it only happens with receivers. Powered speakers aren't affected either, I have a pair of Audioengine speakers that I keep on sometimes 24 hours a day and it's never had any issues. I've used a pair of Genelecs in here and they've never shut down, even on most of the day.

Something is causing A/V receivers to go into protection mode randomly in this room, and I've tested them on 4 different sockets and they all have this issue, either directly plugged into the socket, or using a generic power strip or the Emotiva CMX-2. I figured it was a DC offset issue because I get amp hum if I don't use the CMX-2.

What happens if all other devices connected to that mains group are switched off ? Does it still happen ?
Seems like something may be up in the house wiring, something may be loading that particular mains group in a non-symmetric way.
I would not know why devices would go into protection suddenly when a DC component is present on mains.
I can see humming happening (but may differ over time or happen suddenly and be quiet at another moment).
That can be solved with a DC blocker (up to a small voltage difference).
You can use multiple ones in series if higher DC components need to be removed but will limit the max power that can be drawn.
 

DanielT

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Yeah I don't have shutdown issues with these amps in other rooms. I have a computer and some laptops and a TV in my bedroom and none of these devices have ever experienced shutdowns either, it only happens with receivers. Powered speakers aren't affected either, I have a pair of Audioengine speakers that I keep on sometimes 24 hours a day and it's never had any issues. I've used a pair of Genelecs in here and they've never shut down, even on most of the day.

Something is causing A/V receivers to go into protection mode randomly in this room, and I've tested them on 4 different sockets and they all have this issue, either directly plugged into the socket, or using a generic power strip or the Emotiva CMX-2. I figured it was a DC offset issue because I get amp hum if I don't use the CMX-2.
Talk to an electrician if you have problems with the electrical outlets in the bedroom.Tell the electrician exactly what you wrote here, how it works fine in one room but not in the bedroom.

Have any fuses blown (in your electrical cabinet, where the fuses for the electrical sockets in the bedroom are located)?

Edit:
The electrician can measure how the current looks like in your apartment/house. If you have an old electrical system, it might be a good idea to check it out. You may need to fix it. An electrician knows more about that.
 
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jonfitch

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How about checking loudspeaker wires and loudspeakers?

What would I be checking for? I've switched cables 3-4 times the last few years because I've moved my equipment around. They were always preterminated cables using banana plugs, so there's no exposed wire.
 

solderdude

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It could be caused by anything including HF induction into speaker (or other cables) from nearby wiring of devices.
A device that sometimes switches on/off can induce high peaks locally that may 'enter' devices via any 'path' that may trigger a protection circuit.
It does not have to come via AC mains plug into the used audio gear.. but could.
Could also be a common mode signal thing in which case blockers don't do anything (but may well prevent humming of the gear).
 
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Stokdoof

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Did you monitor the voltage of the mains group or outlet in that room over time ? Maybe it drops below a value over time And the amps are sensitive for that. The laptops you mentioned can handle that very well because of the battery inside. Not sure if there is a cheap option available on the market to monitor and log the voltage of an outlet over time.
 
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jonfitch

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Interesting. I'll start with getting another DC offset blocker first, because somehow I have a feeling it might be more likely a problem on the voltage side. I didn't actually have this problem until about 2 years ago. I recall years ago I had a line conditioner (APC H15) that did automatic voltage adjustment in this room and I never had any amp shutdown issues, but I ended up selling the conditioner for decor reasons (silver finish stood out). So hopefully just an additional DC blocker will solve this. I'll report back if that fixes my problem. Thanks everyone!
 

Vuki

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What would I be checking for? I've switched cables 3-4 times the last few years because I've moved my equipment around. They were always preterminated cables using banana plugs, so there's no exposed wire.
It seems to me like there is some kind of short on the output that forces amps to go in protection mode.
 

GXAlan

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Can give you real time power info on voltage and high frequency noise (which line conditioners can fix). Might be a reasonable diagnostic tool.

Free for State Farm users and some other home owners insurances.
 

DanielT

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Did you monitor the voltage of the mains group or outlet in that room over time ? Maybe it drops below a value over time And the amps are sensitive for that. The laptops you mentioned can handle that very well because of the battery inside. Not sure if there is a cheap option available on the market to monitor and log the voltage of an outlet over time.
In the small summer cottage we have an old type of electrical system with these types of fuses, plugs:
e2011001.jpg

In any case. The stove was malfunctioning. Sometimes completely ok with power, sometimes a few plates, sometimes half and half. I checked the plugs but none were burnt but I replaced them anyway and now the stove works as it should. What I didn't know at the time was that such an old fuse can work but not optimally. It looks perfectly fine as it is not burnt. You can be tricked by that. So it can be smart to talk to an electrician if you have problems with something electrical in the house.:)

Edit:
A stove draws more power than the OP's gadgets messing with him in the bedroom, but still.
 
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antcollinet

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Do the receivers shut down if there is nothing (but power) connected.

Assuming they don't, then connect things in one at a time until it starts happening again.
 

wwenze

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If you share more information about the amp and the rest of the setup, perhaps there can be hints to be discovered somewhere.

The first thing that comes to my mind is common-mode voltage issues caused by problematic grounding.

It'll be useful to know why the amp shuts down too. They don't always tell you why, but if the amp doesn't have certain protection then we can skip investigating those (goddamn gainclone chips with no overheat/overcurrent protection...). Speaking of protection, my amp once tripped due to a badly-encoded .WAV file with huge DC content, so do you happen to have equipment that are DC-coupled, or have a bad capacitor?
 

restorer-john

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You say 'receivers'. Do you have any cable boxes, powered antennas etc attached to these units?

I think there is a common denominator and it's likely not the multiple receivers or the power, unless you have a neutral that isn't a neutral on your supply. Get power looked at straight away and then move on to sources.
 
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jonfitch

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I have two of those devices, and the CMX-2 has LEDs to report if grounding/wiring is correct that as well. All of these devices report wiring as correct.
 
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