Axiom Home Page Forums General Discussion Technical Questions What to do with a problem called Grounding

I am at a loss on what the best move to do is. I have a grounding issue and no idea on what direction is the best move to go.

I have the LFR1100 speakers so they have their own DSP. This is made by Axiom and has been tested and looked at by Andrew and I will assume that he knows what the hell is is doing and not feeling me BS.

I have bought a $1000 Anthem MCA5ii (5 channel 200w8ohm) that has the power to nicely run the LFR's and my VP180 center channel speaker. Sadly however, the MCA doesn't like the Axiom DSP if you connect them via RCA interconnects. One has a floating ground and the other unit does not. So RCA's are out.

I recently upgraded to the Marantz AV7005 pre-amp to get my XLR interconnects so I am not loosing the 12db of power difference by using the RCA - XLR cables to feed the DSP. However, the AV7005 seems to have it's own set of issues the grounding when use with the amp and dsp. If I plug in some equipment with the HDMI I get the feedback humm from the LFR's. My new Panasonic TV gives a small humm on the VP180.

I get ZERO problems of feedback humm from my QS8's that are hooked up through my AudioSource Amp/One-A. This amp does not have any XLR connectors and works fine with even the LFR's but doesn't have quite the power to drive the LFR's at a more reference level.

Before the Marantz, I was using a Pioneer receiver that didn't have any issues with ground feedback humm but lost the -12db due to the MCA / DSP need for the XLR interconnects.

I bought the Marantz used so I can't tell if it is the problem and have no means or desire to throw money at it getting it tested as ground fault issues are the dogs breakfast to resolve. It was the last component to be added. But on the logical side, with new Atmos and DTS-X, the AV7005 is capable of at most 7.2 and no support for the newer standards. I doubt that I will ever go for Atmos but in the next few years maybe the AV8801 will be swapped out by someone and I can pick one up for a better price.

Looking a bit deeper however, the MCA5 doesn't work right with the DSP and this might be the source of the issue. As the Marantz and Axiom DSP play nice with my other amp, perhaps that is the real piece that needs to be solved. But the amp can be a rather expensive piece to replace. Do I replace the 5 channel amp with a pair of matched 2 channel amp that are rated to work down to the 4ohms? Trying to get matched stereo amps used is a good luck endeavor. Crown is a possibility to buy for not too much money. There is Emotiva and Outlaw.. but I can easily see the bill getting up to the 2-3k. And again you are buying blind in the hopes that they will play nice with the Axiom DSP.

The sure fire one that should work would be to get an Axiom amp, but $3000+ for 5 channels it more cost that I would like to spend.

Any thoughts??

Matt, I have been exactly where you are in regards to hum and ground loops. I tried a lot of different things before I got rid of the hum . Hum can drive a guy crazy and I tried a lot of things I found searching the internet. I ended up hooking certain components together on a dedicated power bar and removed the ground lug. Other components were connected to yet another power bar and extension cord to a plugin on a separate breaker. Start your process by keeping to a minimum of components . Cablevision cables are notorious for causing ground loops. In my main system I have zero issues but I am using components from just one company, everything is from Emotiva and using xlr's and is dead silent.

The most frustrating side to this is the room is new custom built. The power plugs are dedicated lines in the same electrical box. The ground wires for the outlets are all twist bound together so they all share the shortest path to a true ground. The cable runs are the same length (< 10' long). All going to a dedicated breaker for each of them.

There is NO cable TV box inside the whole house. How I would love to have just another 10k to put towards getting newer amps and a newer pre-amp but it just aint going to happen.

I was about to build my custom rack for the amps etc.. but thinking now if there are parts that are going to need to change, then why am I spending time to build something that might be the wrong size when it is all done?

I had a major ground loop with my M80 through my power amp.
Have a monster power with ground loop isolator hooked my cable coaxial through the circuit and totally gone. when the coaxial comes loose ground loop returns tighten and good to go.
I'm certain the Axiom quality and performance would kill my monster power centers loop isolator.
Hopefully it's something as easy, try contacting your cable provider they may be able to help, though here in Vancouver when I called to ask Shaw for help they claimed they didn't know what I was talking about.
{DUH what's a ground loop}and that was when I added my HD cable box. You kind of have to let them know you know more of these tech issues than they do!!!

A couple of suggestions:
The Emotiva CMX - http://hometheaterhifi.com/editorial/blogs/little-things-trouble-hum/

The Ebtech Hum Eliminators - http://www.ebtechaudio.com/hedes.html

Do you still have hum if you take the DSP out of the signal chain? If the hum does go away using an Ebtech HumX with the DSP should help.

use a two prong extension cord to lift the ground to see if that helps.

Shaw knows full well about it - they just won't admit it unless you are very persistent. From what I've heard, they have ground isolation gizmos but they don't normally give them out for some reason.

I had hum problems in the past & after much experimentation & troubleshooting, it indeed was Shaw's cable installation in my house...

TAM

A few points.

I do not have CABLE TV.

The power cords from all my equipment are all like a C13 plug without the ground pin. So there is zero value with using some ground cheater plug as the amp and pre-amp don't even use the ground pin on a plug at all.


I guess I am coming to the realization that even though the MCA5ii is a fantastic sounding amp, it just doesn't play nicely with the Marantz pre-amp. It works fine with my old Pioneer receiver.

I will just have to see if I can re-sell the unit to recoup the $1000 I put into buying it, and then put that money towards something other. The problem is that the speakers are all 4ohm and that puts you into a certain bracket of amp that you can buy.

There just isn't enough money for all the toys. I was fortunate enough to have gotten my amps when our dollar was in better shape. Don't feel bad the tv I want is 8Grand ,shame plasma's had to go away. I can barely stand to watch a LED tv.

Can you be specific how you wired your room.

I think you said you did split plugs with a shared neutral. Is this the case?

Send me a pm if you want. You sound fairly competent in electrical, so I'm willing to talk you through the issue on the phone if you want. A lot faster than message tag online.

A nights sleep and you get to think about what you have and what your options are.

Right now it looks like the MCA is going to get boxed up and replaced by something else. The big question is what.

I will give Axiom a call and see if Ian can convince me that their amp is the direction to go.. but the cost vs performance just seems to be a bit too large of a barrier to get over. For the same cost as getting 5 channels from Axiom, I could order in an Outlaw 7 channel amp + Marantz AV7702

There is a local dealer of Emotiva and I could buy into their XPA-7 that would give me 5.1 from the single amp with the extra two channels needed for the LFRs.

For a far less outlay, I could purchase 2 Crown XTi800 to power the LFRs and use the two Amp/One for surround, and center by monoblocking the second unit to get 200w @ 4ohm.

I remember that one of the members here who moved to LFRs went with the Crown amps and didn't have bad things to say about that option. It might be the better choice as the cost is minimal and leaves me some room to look into moving to a newer pre-amp like the Yamaha CX-A5100 in a few years as the room is setup to run 11.2. who knows by then it might be worth while to look in that direction.

If you have hum from other stuff (TV hdmi) the issue could be a simple electrical reconfigure. May cost $0.

I'm thinking it's your cable TV.

Hi Matt,

I'm sorry to hear that you are still having issues with hum in your system. Just for the record, the Axiom DSP has a three prong plug only for the safety earth connection to the metal chassis as it is not double insulated and hence a safety (and legal) requirement. The signal ground is floating relative to the safety (AC) earth, so it cannot be creating a ground loop in the typical sense. I don't want to question Anthem's design, but I find it very strange that they do not use a three-prong power connector. The reason I find this strange is that high power amplifiers almost always have a safety ground connection. From the photos I can find of the back of the MCA5, it does have CSA electrical approval, but it does not have a double-box double insulated logo on it anywhere. I don't know how this would have passed CSA approval without either having a safety earth connection OR being double insulated. I also find it very strange that they specifically recommend using the XLR inputs over the RCA inputs. Any amplifier that offers both should perform equally well with either input that is offered. None of that is going to help you with your problem, so before you jump to put anything up for sale, there are some simple things that should be tried:

Disconnect all inputs to the AV7005, but leave the DSP and your two power amps in the equation. Hum?

If yes, disconnect the outputs from the AV7005 to your AudioSource amp. Hum?

If yes, remove the DSP and connect FIVE pre-outs from the AV7005 to your MCA5 (maybe use the surround L/R to connect to the LFR rear sections for this test. Hum?

If yes, the MCA5 is the issue. If no, try connecting FIVE RCA pre-outs from the AV7005 (disconnect the XLRs). Hum? If yes, the MCA5 is the issue.

If you do get hum with either of these configurations with no inputs connected to the AV7005 and the DSP out of the loop, try connecting a wire from the ground screw on the back of the MCA5 to the phono ground on the AV7005. See if that changes the hum level at all.

Thanks,

Andrew

Is the secondary usually connected to chassis ground in electronics? I always thought it was the primary only and the secondary was floating -as in the Axiom amp.

Trying to understand the bonding jumper.

There is a long standing issue between the MCA and the Axiom DSP. This was discussed for a bit with Andrew last year and if I plug in an RCA cable between the DSP and the MCA with nothing else connected. (ie not even a Pre-Amp hooked up) the MCA generates a ground loop humm. If I used an XLR cable, then that humm was eliminated.

Since those tests, I bought myself another two cheeper amps that I was going to use for surround channels as I got a new pre-amp as I was using a receiver before that has pre-out connectors.

The new amps can be hooked up to the DSP via RCA and they generate ZERO humm. SO I know that the MCA is not playing nice with the Axiom DSP.

I have been playing with the Marantz AV7005 and it has it's own funny quirks. I have a couple mini HTPC boxes that I used to run linux and my KODI and another to run a music media player on. For some reason, these pc's hooked up to the Marantz make funny noises through the speakers when the hard drive or network is accesses. I can take the same pc's and hook them into my old Pioneer receiver and it makes no sound what so ever.

I am now thinking longer term. Simply sell off the AV7005 and MCA5 amp and recoup my money that was spent on them, the theoretical added sound benefit I got from them vs the aggravation and trouble is not worth it. I have the old Pioneer receiver and with the two Amp/One that I have can run the LFR's

I can look into getting a better set of crown amps, or something different in the future. I can sit tight for the time being and just enjoy my music and TV with the old equipment that I have and wait for 2-3 years for Atmos and DTS-X to become common old school or die out replaced by something better and upgrade to them later for hopefully cheep.

No! True Audiopiles not have time for wait and enjoy music. You play cable bingos like Andrew show and make much posts here.

Reflect!