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Emotiva CMX-2 "AC line filter with DC offset eliminator" - seeking opinions/reviews

DonH56

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Would this also be suitable to use to power my cable internet modem and router?

Suitable, sure, but should not make any difference to those components... If you are using it as a power strip it won't hurt anything to plug them into it.

This raises a semi-interesting point for the members who might know: if I build or buy a strip with DC blocking at the input, does that provide any isolation of other components that might inject DC or steady-state offsets (that may look like DC in an rms way) after the blocking caps? E.g. a big switching power supply that is not well-designed can do strange things to the line (I have seen this with some industrial equipment, not something I have tried to measure in an audio system)... I suspect nay. I do not know what specs are for injecting noise into the line or otherwise imbalancing the load so maybe a total non-issue, curious.
 

yodog

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What's the problem with your present power supply/s for your cable internet modem and router?

nothing really except that I read someone’s review online that said they swapped out their power strip that powers their cable modem and router and now when streaming music it sounded much better, compared to the power strip they were using which was and is the same one i am using right now, which is the furman pst-8d.

I believe them because I tried plugging my HomePod into this strip before and it made all music sound robotic like and just not enjoyable to listen to. I ended up plugging my HomePod to the less expensive furman pst-6 that does not feature some of the more advanced filtration and protection technologies furman advertises and music sounds just fine. So I was thinking I could improve the sound quality of my music when I stream to my audio system if I change out the power strip to this dc offset device. I was also thinking of getting a second one for my power amp and pre amp....

These are just my honest opinion and thoughts, don’t know if I am on the right track or vastly off course. Any constructive advice or thoughts would be appreciated and welcomed, cheers
 

AnalogSteph

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nothing really except that I read someone’s review online that said they swapped out their power strip that powers their cable modem and router and now when streaming music it sounded much better, compared to the power strip they were using which was and is the same one i am using right now, which is the furman pst-8d.
Sounds like a load of bollocks to me. Telecoms equipment like that uses switch-mode wall warts these days, usually double-insulated with no PE contact at all, and as long as live and neutral are connected, these will work fine with little regard to mains quality, even on all DC - they need a DC isolator about as much as a hole in the, erm, case.
It would merely be nice if mains filter leakage currents had somewhere to go to - usually they'll make their way over shielded patch cables to the nearest device that has its chassis ground connected to PE. Perhaps you don't want any unbalanced audio connections in that particular path. Should be easily accomplished by strategic use of an unshielded patch cable if need be. The actual twisted pair data lines are galvanically isolated inside Ethernet devices, so internal ground potential can be floating wherever it wants within a window of several hundred volts at least.

I'd say if however you plug in your telecoms equipment makes any (real, not imagined) difference whatsoever, there is a major issue in your playback system that needs to be rectified. Probably some sort of ground loop that for some reason encompasses an unbalanced audio connection. It can be hard to combine the world of networking (IEC Class I, i.e. earthed more often than not) with the world of home audio (IEC Class II, i.e. double insulated and floating) without trouble, especially if there is an antenna connection involved as well (generally earthed). Bad grounding practices inside devices plus ground loops can lead to twitchy USB or HDMI connections that drop out upon any major kind of disturbance on the mains, despite using differential signalling that should normally be pretty much immune to such things (unlike unbalanced audio).
Identifying potential trouble spots pretty much takes a connection diagram of the entire system, with any ground / shield connection including mains PE and ideally the type of power supply as well.
 

DonH56

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I believe them because I tried plugging my HomePod into this strip before and it made all music sound robotic like and just not enjoyable to listen to. I ended up plugging my HomePod to the less expensive furman pst-6 that does not feature some of the more advanced filtration and protection technologies furman advertises and music sounds just fine.

<Elided, can't decide if this is just trolling or a legitimate question. If the latter, look to other reasons than the power strip, like your mood when you listened or perceptual bias.>
 

Speedskater

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nothing really except that I read someone’s review online that said they swapped out their power strip that powers their cable modem and router and now when streaming music it sounded much better
Audiophiles write things like that all the time. But their posts lack due diligence and they never support their comments.
 

Omar Cumming

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I have a power amp (Emotiva LPA-1) that had an audible mechanical transformer hum when no signal was present. After installing the CMX-2 between the mains power and the amp the hum was gone. Very pleased.
 
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DonH56

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The wholesale change to toroidal transformers saves space and reduces EM coupling, so you can cram things tighter in the chassis, but it is very difficult to integrate an air gap in the transformer core. As a result, they saturate earlier, and are more sensitive to line DC (etc.) issues that can cause the core to saturate (leading to all sorts of generally bad things audible and not).
 

Kal Rubinson

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Would this also be suitable to use to power my cable internet modem and router?
Why not? OTOH, I prefer to use a small UPS for modem and router to avoid resets due to the occasional voltage sag or interruption.

P.S.: I use the CMX-2 on my OLED display.
 

yodog

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Why not? OTOH, I prefer to use a small UPS for modem and router to avoid resets due to the occasional voltage sag or interruption.

P.S.: I use the CMX-2 on my OLED display.

Because at the time when I wrote that I had an unknown hum issue. Since then I swapped out the gear and upgraded to better gear and now I don’t have any hum issues.

And now i don’t have a desire to connect my modem and router to a cmx-2. Right now I have them connected not to a UPS, never actually had a UPS before, but I have them connected to a Furman P-1800 AR, which at least should prevent any voltage sag issues im hoping.

what I find strange is, when I connect my modem and router to my at the moment unused Furman PST-8D power conditioner strip, my music sounds different. It’s very obvious but I can’t really describe it or put it into words. I also can’t decide which “version” I like better. Nonetheless I have them connected to my netgear cm1000 modem/r9000 router which are connected to each other and to my node 2i with Wireworld Starlight 8 ethernet cat8 cables and I figure I’ll just use the more expensive Furman P-1800AR for the time being...

Sorry for the ramble but I thought I’d share my thoughts because, well why not? Cheers everybody! I hope you all are having or will have a good week/remainder of the week :)
 

jts

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I have a Heed Obelisk Si MK3. I have been experiencing intermittent transformer humming from this amp. This is a mechanical hum from the amp itself. It does not present in the speakers or pre out of the amp.

I tested the amp with all the circuits off in my house except one, on which the only thing plugged in was my amp. I still encountered the humming sound.

I sent it in for service and the techs reported that the amp was silent and in perfect condition. A colleague mentioned I might have a DC offset issue in my ac line which could cause the toroidal transformer to hum.

I purchased an emotiva cmx-2 and my amp is now completely silent. There is no longer any noise coming from the amp at all. Problem solved.
 

tmtomh

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I have a Heed Obelisk Si MK3. I have been experiencing intermittent transformer humming from this amp. This is a mechanical hum from the amp itself. It does not present in the speakers or pre out of the amp.

I tested the amp with all the circuits off in my house except one, on which the only thing plugged in was my amp. I still encountered the humming sound.

I sent it in for service and the techs reported that the amp was silent and in perfect condition. A colleague mentioned I might have a DC offset issue in my ac line which could cause the toroidal transformer to hum.

I purchased an emotiva cmx-2 and my amp is now completely silent. There is no longer any noise coming from the amp at all. Problem solved.

I purchased a Van Alstine DC blocker rather than the Emotiva, but my experience is otherwise the same as yours. My power amp, an Adcom GFA-5400, would exhibit a low-volume (but audible from my listening position during moments of total silence between songs) hum. Per many online descriptions of the effect of DC offset on toroidal transformers, the hum would slowly build, and then get quieter, and then slowly build again, in a cyclical fashion.

I tried all the troubleshooting measures you describe and more, and confirmed that it was a mechanical sound from the enormous toroidal transformer inside the amp, which did not transmit through the speakers and was unaffected by the presence or absence of any other equipment in my system or home. The DC blocker fixed the issue - no more hum.
 

DonH56

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Toroids are more sensitive to DC than standard EI transformers. Without an air gap, the core saturates with far less current, and DC current simply eats up headroom leading to ugly waveforms and hum/noise. Toroids do better constrain the EM field around the transformer so are better in tightly-packed boxes and with less shielding. Always trades.
 

Certainkindoffool

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I purchased a Van Alstine DC blocker rather than the Emotiva, but my experience is otherwise the same as yours. My power amp, an Adcom GFA-5400, would exhibit a low-volume (but audible from my listening position during moments of total silence between songs) hum. Per many online descriptions of the effect of DC offset on toroidal transformers, the hum would slowly build, and then get quieter, and then slowly build again, in a cyclical fashion.

I tried all the troubleshooting measures you describe and more, and confirmed that it was a mechanical sound from the enormous toroidal transformer inside the amp, which did not transmit through the speakers and was unaffected by the presence or absence of any other equipment in my system or home. The DC blocker fixed the issue - no more hum.

I had a cheap headphone amp with preouts that would hum incessantly when used - headphone and line out were fine though. A powerline filter stopped that hum.

I also have some PS Audio monoblocks in which someone replaced the capacitors with larger ones. They both physically hum, but are dead quiet out of the speaker. Powerline filter does nothing for this.

They also dim the lights when turned on, and will flip the breaker if they are both turned on at once. Guessing they need a slow start circuit.
 

jester7677

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Thought I would add my 2 cents. Had a transformer buzz that would come and go in my 7 channel amp. Sometimes it would be audible from the speakers as well. Would randomly occur and would definitely occur when my wife uses her flattening iron in a bathroom upstairs, on a different circuit.

CMX-2 has made the system dead silent and it’s wonderful.
 
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