3 prong to 2 prong adapter

[gus4emo]

Hi all, so I saw this guy on YouTube saying to try one of those to plug the amplifier in, the first step to get rid of hum...my thing is, it's not the amp, I unplugged the rca, and the hum is not there, but is it safe to plug the CMX6 into it, no equipment with 3 prongs is connected to the CMX6, but the CMX6 seems to be the culprit, I can't get rca cables far enough from it, some channels still have some hum, so, is it safe to try the adapter, I mean, if it works, is it safe to then leave it plugged into the adapter....

[ttocs]

Remember, everything connected can carry a ground to somewhere else.

I had a hum ONLY when I used the speaker level connection on my subs from the Left/Right amps. One night I decided to find what was causing it. After unplugging all the power cords and HDMI cables, I started with only the XMC-1, one amp, and one sub, - no hum. As soon as I connected the projector the hum returned! That was really easy.

The PJ is on a non-isolated ground circuit, but all the other A/V circuits are isolated ground. The HDMI cable is what carried the ground from the PJ thus causing the hum. I stopped trying to use the speaker level connection to the subs until I pulled a ground wire, but have yet to do so because I don't need the PJ anymore.

The moral of this story is try to check everything to see what is causing the ground imbalance.

[gus4emo]

Jun 8, 2020 16:32:43 GMT -5 ttocs said:

Remember, everything connected can carry a ground to somewhere else.

I had a hum ONLY when I used the speaker level connection on my subs from the Left/Right amps. One night I decided to find what was causing it. After unplugging all the power cords and HDMI cables, I started with only the XMC-1, one amp, and one sub, - no hum. As soon as I connected the projector the hum returned! That was really easy.

The PJ is on a non-isolated ground circuit, but all the other A/V circuits are isolated ground. The HDMI cable is what carried the ground from the PJ thus causing the hum. I stopped trying to use the speaker level connection to the subs until I pulled a ground wire, but have yet to do so because I don't need the PJ anymore.

The moral of this story is try to check everything to see what is causing the ground imbalance.

So, I got a ground loop isolator for the surround back right channel, it didn't work until I pulled it at least 6 inches from the CMX6...

[garbulky]

The CMX-2 (not the CMX-6) has a thing that takes out DC offsets. Not saying it will help in your case. Which amp is it? The PA-1 amp has some user reported issues of causing a buzz or hum with RCA inputs. I don't know the answer to the 3 prong to 2 prong adapter. Maybe KeithL can shed some light.

[boomzilla]

Emotiva has stated to me that the ground prong is academic for the PA-1 amplifier. This is NOT a general statement about OTHER Emotiva electronics, but specific to the PA-1 only. Apparently, the CMX-6 has a transformer in it that is causing hum in proximate signal wiring? There are a number of ways to avoid that:

1. Use balanced XLR cables rather than unbalanced RCA ones
2. Route unbalanced RCA cables away from the CMX-6 and any other equipment that has AC
3. Use highly-shielded RCA cables - their capacitance per foot will be higher, so keep them as short as possible (good advice even if hum is not a problem)
4. Use a hum interruptor device that claims to reduce hum
5. Use "star grounding" such that one and only one device in the system is grounded and all other system devices ground through their RCA cable shields to the central device
6. Plug all devices into the same wall socket - different sockets may have different resistances to ground, creating hum
7. Take a break - drink a beer - go outside & exercise - and then tackle the problem again - hum can be frustrating
8. Google the problem - others may have innovative methods for hum reduction that I've never heard of

Best of luck!

[gus4emo]

Jun 9, 2020 1:57:02 GMT -5 boomzilla said:

Emotiva has stated to me that the ground prong is academic for the PA-1 amplifier. This is NOT a general statement about OTHER Emotiva electronics, but specific to the PA-1 only. Apparently, the CMX-6 has a transformer in it that is causing hum in proximate signal wiring? There are a number of ways to avoid that:

1. Use balanced XLR cables rather than unbalanced RCA ones
2. Route unbalanced RCA cables away from the CMX-6 and any other equipment that has AC
3. Use highly-shielded RCA cables - their capacitance per foot will be higher, so keep them as short as possible (good advice even if hum is not a problem)
4. Use a hum interruptor device that claims to reduce hum
5. Use "star grounding" such that one and only one device in the system is grounded and all other system devices ground through their RCA cable shields to the central device
6. Plug all devices into the same wall socket - different sockets may have different resistances to ground, creating hum
7. Take a break - drink a beer - go outside & exercise - and then tackle the problem again - hum can be frustrating
8. Google the problem - others may have innovative methods for hum reduction that I've never heard of

Best of luck!

I will try to pull apart all rca cables again, now, everything plugged into the CMX6 is NOT grounded, can it be getting the hum from the outlet, I have the 3 to 2 prongs adapter, should I try to plug the CMX6 into it?

The beer will be available...lol..

[boomzilla]

Were it me, I'd NOT unground the CMX6. I think it needs its ground prong to do surge suppression (but I could be wrong).

[cawgijoe]

I agree with Boom.....the three prong plug is there for a reason....using a 2 prong cheater is really not the way to go if you can help it.

Unfortunately finding that hum is a painful process of starting from scratch and plugging stuff in till you can hear it to discern the ground loop culprit.

[megash0n]

Jun 9, 2020 11:31:36 GMT -5 boomzilla said:

Were it me, I'd NOT unground the CMX6. I think it needs its ground prong to do surge suppression (but I could be wrong).

I'm almost certain the CMX6 isn't a surge protector.

[gus4emo]

Jun 9, 2020 11:39:53 GMT -5 cawgijoe said:

I agree with Boom.....the three prong plug is there for a reason....using a 2 prong cheater is really not the way to go if you can help it.

Unfortunately finding that hum is a painful process of starting from scratch and plugging stuff in till you can hear it to discern the ground loop culprit.

It's painful alright....the hum for the most part is not too loud, and not on all channels, but I have gone one rca at a time to unplug it, and the hum disappears, so it's not the amp...

[ttocs]

Jun 9, 2020 13:39:32 GMT -5 gus4emo said:

Jun 9, 2020 11:39:53 GMT -5 cawgijoe said:

I agree with Boom.....the three prong plug is there for a reason....using a 2 prong cheater is really not the way to go if you can help it.

Unfortunately finding that hum is a painful process of starting from scratch and plugging stuff in till you can hear it to discern the ground loop culprit.

It's painful alright....the hum for the most part is not too loud, and not on all channels, but I have gone one rca at a time to unplug it, and the hum disappears, so it's not the amp...

If I'm understanding you, you are leaving everything connected and removing one item at a time? This is a nightmare scenario.

Start with everything disconnected. Everything. No power cords connected. No HDMI connected. No speakers connected.

Then start with the pre, amp, and one speaker at a time. Use the tuner if it's built-in and you want some sound, or then connect a source. But definitely start with all the speakers before other sources. I've done this the nightmare way lots of times in different residences with no positive outcome, and I've done it the All-Disconnect way - with two different system setups in the house - and building to the hum is the only method that works.

[millst]

Don't ever use a cheater plug for anything besides temporary troubleshooting. You are risking electrocution by lifting the ground. They aren't really even recommended when used properly (with the ground tab connected).

[KeithL]

This is actually a somewhat complicated topic... so let me see if I can inflict a little clarification on it...

1)

A lot of our gear is effectively "double insulated" - which means that it is in fact safe to use with the ground prong disconnected.

However it is always safer not to disconnect the ground unless you know for sure.

(And, yes, it can be quite dangerous with some gear.)

2)

In the old days a lot of gear was designed without a specific ground side - and with non-specific two-prong plugs.

And, with a lot of that old gear, you would often get less hum with the plug one way or the other.

And, since there was no "safety key", you had no way of knowing which way, if either, was safer anyway.

(But a lot of that old gear would also give you a nasty jolt if you were foolish enough to touch it while leaning against a water pipe.)

(And, if that happened, connecting a ground wire from a screw on the chassis to a real ground would often fix it.)

3)

Our CMX-2 and CMX-6 do actually have surge suppressors in them...

And, as with most surge suppressors, you WILL render the surge suppression capabilities ineffective if you lift the ground.

4)

DC offset is a very specific issue and, when it occurs, it will often cause a power transformer to run excessively warm, or to hum more than usual.

This will usually be mechanical hum coming directly from the transformer.

It is UNLIKELY to cause hum to come from the speaker.

5)

A single poorly shielded or defective interconnect cable can indeed pick up significant hum from surrounding sources.

And even good quality interconnects can pick up hum if you run them next to a power cable or other strong source of noise.

Balanced interconnects are much better at avoiding this... but even they can pick up noise under some conditions.

And some audio gear itself can pick up noise if located too close to a source of noise.

(Which is why it's still a bad idea to put your phono preamp on top of your power amp.)

6)

A GROUND LOOP is especially difficult to locate and fix because it is caused by the relationships between multiple connections.

It is quite common to have cables, none of which individually has any hum, but which hum when connected in certain combinations.

And, if you try to figure this out by disconnecting cables one at a time, you will go crazy without finding the solution.

7)

One solution that often helps with ground loops is to experiment with various power connections...

If your preamp and power amp are connected to separate outlets try connecting them to the same power strip...

And, if they're connected to the same outlet, try different ones...

There is no method that is "always best" but often one or another will fix the problem.

8)

Another solution is to ground the equipment separately...

Try connecting a wire from a chassis screw on the amplifier or preamp to a true ground (like a water pipe or the ground screw on an electrical outlet).

Try connecting chassis screws on various pieces of equipment, like a preamp and a power amp, together directly.

Again, while there is no obvious correct solution, you may find that one eliminates your problem.

9)

Finally, and especially if we're talking about very small amounts of hum, you may need to look at multiple solutions.

There may not be a single cause...

And, if that's the case, you may need to look for multiple solutions, each of which "helps a little bit"...

10)

Finally remember that ALL ELECTRONIC CIRCUITS HAVE AT LEAST A TINY BIT OF NOISE.

(So, if you only hear a tiny bit of hiss or hum, when your ear is right next to the speaker, it's time to stop fussing and listen to some music. )

[westom]

Jun 9, 2020 13:39:32 GMT -5 gus4emo said:

It's painful alright....the hum for the most part is not too loud, and not on all channels

Unfortunately confusion exists because you are trying to fix a defect without first defining it. Don't do that. Fixing comes much later. First reasons for a defect and its symptoms must be defined. Without making any effort to fix anything.

Item A connects to item B. Item B connects to item C. Item C may then connect to A via any path (or parallel paths); even via a safety ground.

An isolator to separate the B to C connection. Is that where the defect is? Of course not. That is only one part of the ground loop. Not find the other paths in that loop. First the ground loop must be defined. Much later, we discover the defect is in A.

Step one. Identify every part in that loop. Solution means taking each part of the problem one step at a time. Once all those steps have provided facts, only then do we know what is defective. And much later, we then discover a solution.

Again, your strategy has created confusion. Even wild speculation is about AC currents that have no relationship to typical ground loops - are only a symptom of that defect. Step one - use various tools to determine the loop.

Another tool (never a solution) is a UPS. Power each component from a UPS not connected to any receptacle. Does that also break a loop? A two prong to three prong adapter is also a tool - and never a solution. Does it break that ground loop?

Once you have facts (not tests based only in speculation), then others who really know this stuff can finally post something. Your replies will only be a useful as facts that you first provide. Demonstrated is how to enable the better informed. Stop making conclusions (ie about magic AC power boxes). Only report what was observed by testing.

[gus4emo]

Jun 9, 2020 15:33:26 GMT -5 KeithL said:

This is actually a somewhat complicated topic... so let me see if I can inflict a little clarification on it...

1)

A lot of our gear is effectively "double insulated" - which means that it is in fact safe to use with the ground prong disconnected.

However it is always safer not to disconnect the ground unless you know for sure.

(And, yes, it can be quite dangerous with some gear.)

2)

In the old days a lot of gear was designed without a specific ground side - and with non-specific two-prong plugs.

And, with a lot of that old gear, you would often get less hum with the plug one way or the other.

And, since there was no "safety key", you had no way of knowing which way, if either, was safer anyway.

(But a lot of that old gear would also give you a nasty jolt if you were foolish enough to touch it while leaning against a water pipe.)

(And, if that happened, connecting a ground wire from a screw on the chassis to a real ground would often fix it.)

3)

Our CMX-2 and CMX-6 do actually have surge suppressors in them...

And, as with most surge suppressors, you WILL render the surge suppression capabilities ineffective if you lift the ground.

4)

DC offset is a very specific issue and, when it occurs, it will often cause a power transformer to run excessively warm, or to hum more than usual.

This will usually be mechanical hum coming directly from the transformer.

It is UNLIKELY to cause hum to come from the speaker.

5)

A single poorly shielded or defective interconnect cable can indeed pick up significant hum from surrounding sources.

And even good quality interconnects can pick up hum if you run them next to a power cable or other strong source of noise.

Balanced interconnects are much better at avoiding this... but even they can pick up noise under some conditions.

And some audio gear itself can pick up noise if located too close to a source of noise.

(Which is why it's still a bad idea to put your phono preamp on top of your power amp.)

6)

A GROUND LOOP is especially difficult to locate and fix because it is caused by the relationships between multiple connections.

It is quite common to have cables, none of which individually has any hum, but which hum when connected in certain combinations.

And, if you try to figure this out by disconnecting cables one at a time, you will go crazy without finding the solution.

7)

One solution that often helps with ground loops is to experiment with various power connections...

If your preamp and power amp are connected to separate outlets try connecting them to the same power strip...

And, if they're connected to the same outlet, try different ones...

There is no method that is "always best" but often one or another will fix the problem.

8)

Another solution is to ground the equipment separately...

Try connecting a wire from a chassis screw on the amplifier or preamp to a true ground (like a water pipe or the ground screw on an electrical outlet).

Try connecting chassis screws on various pieces of equipment, like a preamp and a power amp, together directly.

Again, while there is no obvious correct solution, you may find that one eliminates your problem.

9)

Finally, and especially if we're talking about very small amounts of hum, you may need to look at multiple solutions.

There may not be a single cause...

And, if that's the case, you may need to look for multiple solutions, each of which "helps a little bit"...

10)

Finally remember that ALL ELECTRONIC CIRCUITS HAVE AT LEAST A TINY BIT OF NOISE.

(So, if you only hear a tiny bit of hiss or hum, when your ear is right next to the speaker, it's time to stop fussing and listen to some music. )

Thanks Keith, I am certain it's not the XPA7, I got an isolator from a forum member, I connected it to the loudest channel humming,
surround back right, nothing changed, then pulled it from the CMX6 at least 6 inches, hum is gone, even pressing my ear against the speaker, is gone! The receiver, which I'm using only the preamp section, is connected to the CMX6, the receiver is 2 prong as is everything connected to the CMX6....I have a wire connection from a screw on the receiver to the XPA7, on a screw as well...

[vcautokid]

At the end of the day the CMX is an electronic device and can be a noise source. I have a couple and fortunately has not been the case. The days of death quiet coming out of your speakers get harder with all the digital schiit we keep including in our circuits. Computers microwaves anything that makes noise. I agree with Keith and as long it is not omnipresent, probably not worth stressing but keeping certain components away from each other helps just as keeping signal cables away from power cables. Amazing how I still see people bundle power and signal cables together and wonder why there is noise. We live in an interference world these days. So best practices have to be in play.

Now ground loops and other noise can be a pain in the a$$.I fought Charter cable for a decoder box and cable that created hum noise. They wouldn't fix it. So I did. I cancelled their service and the noise went away, and then it really went away when I went away and moved.

[mgbpuff]

The reason that a cable box is often the cause of hum is that the cable co. installers insist on grounding through a grounding rod that they install near the cable entrance. This rod may be very far from your whole house electric system ground, thus a voltage difference between the two grounds can occur causing circulating currents and hum.. Running a grounding wire from the cable entrance to your electrical system ground or to a water pipe (often used for the system ground) will fix the problem. The cable co. won't do this because it conflicts with their installation policy and training.

[vcautokid]

Lets also not confuse mechanical noise though this is resolved as I can tell, mechanical noise for a differing ground potential. Laminar Core transformer when fed even small amounts of DC have a symptom known as "Lam Rattle". The laminate core actually rattles. Torroids will just vibrate in the chassis.

Vs. Differing electrical ground potential often seen in anything electronic. Had to trouble shoot for my camera shoot here for a buzz and sure enough HDMI was the reason. Nice.

[westom]

Jun 10, 2020 7:52:51 GMT -5 mgbpuff said:

This rod may be very far from your whole house electric system ground, thus a voltage difference between the two grounds can occur causing circulating currents and hum.. Running a grounding wire from the cable entrance to your electrical system ground or to a water pipe (often used for the system ground) will fix the problem.

Code is clear about this. A necessary ground for TV cable, OTA antenna, telephone, and AC electric must be same. That coax cable must drop down to the common earth ground electrodes before entering a house. This might reduce noise. But is essential to protect humans and so that appliances are not damaged by transients.

An AC utility demonstrates these good, bad, and ugly (preferred, wrong, and right) solutions at:
www.duke-energy.com/energy-education/power-quality/tech-tips
then select Tech Tip 8.

Water pipe is the only earth ground that is a code violation if other earthing electrodes do not exist. That cable wire should be rerouted by the cable company so that it connection to those common electrodes is less than 10 feet. A long grounding wire between two separate electrodes would provide human safety (if sufficiently buried at least 18 inches and thick enough as required by code). But what remains a best solution is what a cable installer should have done right the first time.

[gus4emo]

Jun 10, 2020 9:55:17 GMT -5 westom said:

Jun 10, 2020 7:52:51 GMT -5 mgbpuff said:

This rod may be very far from your whole house electric system ground, thus a voltage difference between the two grounds can occur causing circulating currents and hum.. Running a grounding wire from the cable entrance to your electrical system ground or to a water pipe (often used for the system ground) will fix the problem.

Code is clear about this. A necessary ground for TV cable, OTA antenna, telephone, and AC electric must be same. That coax cable must drop down to the common earth ground electrodes before entering a house. This might reduce noise. But is essential to protect humans and so that appliances are not damaged by transients.

An AC utility demonstrates these good, bad, and ugly (preferred, wrong, and right) solutions at:
www.duke-energy.com/energy-education/power-quality/tech-tips
then select Tech Tip 8.

Water pipe is the only earth ground that is a code violation if other earthing electrodes do not exist. That cable wire should be rerouted by the cable company so that it connection to those common electrodes is less than 10 feet. A long grounding wire between two separate electrodes would provide human safety (if sufficiently buried at least 18 inches and thick enough as required by code). But what remains a best solution is what a cable installer should have done right the first time.

I have a DTV MiniGinnie (I think that's how it's spelled, lol) right on top of the receiver, I will check that out too.