help USB hum

[beerandmusic]

driving me nuts....

 

i keep getting hum out my usb port...it seems if i wiggle the cable the hum will get quieter and louder, but cant get it to go away.

tried different cables, different usb ports...

 

for testing using pc out to dragonfly to cable to amp

 

check this out...

 

if i play my android phone connected to the amp, no hum.

play the same phone, same connection, but hook the usb cable to my phone from my computer (like to charge it), the hum returns.

 

i even tried 3 different computers

the two different desktops both caused hum

the laptop running on battery, no hum

 

what up???

[audio.bill]

Sounds likely to be a ground loop, caused by a different ground potential being introduced from the PC when powered by your AC. You can try a cheater plug (3-prong to 2-prong AC plug adapter which you can get at any hardware/electrical supply store) on the power cord for the PC to see if that eliminates the problem. If it does then you have to decide if you're willing to operate the PC with the ground connection floating as the adapter allows for, or if you want to try to track down another possible solution which would allow you to leave the ground connected.

[beerandmusic]

thanks for the suggestion..i just now tried your suggestion...no difference.

 

i dont mind putting the "cheater plug" on my pc end, but don't want to put it on my amp end. i just got the amp back from repair, maybe it is at the amp end...the repair tech (mcintosh authorized), said he had no hum issues when he tested it....it's a $2500 amp and $600 repair bill so i do want to know for sure there is no problem with the amp...i didnt seem to have the problem with my denon reciever....but the amp does sounds great under other scenarios e.g. cd (albeit the cd was powered from same outlet as amp), tablet or android (as long as no usb connection), and laptop usb port (running from battery, never tested with power connected).

 

problem does seem to be desktop usb which is on different outlet.. but even when i ran a power striip from same outlet as amp to my pc, i still get the hum.....

 

this has been driving me nuts for 6hrs already! I don't want to give the mcintosh my blessing as 100% until i can figure this issue out.

[AlainGr]

Would it be possible for you to bring your PC, dac and amp at the repair shop ? Or to a friend's place near you ? I know it is not practical, but... I know what you are into, I have had my share of ground loops. When I had one, getting rid of it was a game of patience. Putting a cheater to one component, then the other, etc... And when I thought the problem was solved (in my situation, lifting the earth on the amplifier), then a second ground loop appeared at the subs level... What a mess

[beerandmusic]

ok, so i grabbed a 4th pc (a portable vivopc), plugged into same outlet as amp, and when i connect the usb cable to the tablet, NO HUM.

 

so now the question is, what the f is this ground loop and what do i need to do to fix it?

 

my main pc (that i want to use) is too far from the amp to plug in same outlet, and don't want to run an extension cord ....

 

i guess i could buy an external dac and plug the dac into same outlet as amp and that should solve it? but maybe not? would rather know how to fix this ground problem if thats what it is....

 

also still curious why i didnt have this problem when i used a denon reciever instead of this repaired mcintosh amp.

[AlainGr]

Hi Beerandmusic.

 

You are right. Before investing in other components, it would be a good thing to pinpoint the culprit for the ground loop (if it is a ground loop). If you run an extension just for the sake of your search, maybe it will bring some answers ?

 

At some point, what I did was this to narrow the identification of the problem:

- I detach all AC cables from components that have no direct relation with the sound system (if they are plugged in the same wall AC) and also the interconnects.

- I disconnected the subs also (AC and interconnects).

- I got as many cheaters as there were components. All individually. Do not do this on the main connection of a powerbar, as the grounds are generally all tied together on the same rail inside the powerbar...

- Once I have the minimum components required to play music, I disconnect, starting from the PC, up to the power amp (or the receiver).

- If you have a power conditionner, do not forget to remove it also (just in case)

 

And when nothing seemd to point to any of the components, here is the extreme...

- I shut all the breakers in the house, except for the ones that require power for the sound system.

 

Yeah, I know, there is not a lot of fun in doing this, but the less components you have to check, the easier it gets to identify the potential source of the problem. This will not necessarily explain why it is happening, but as least you will maybe have a starting element of the answer...

 

To tell you: I never was able to solve my subs ground loop problem. When I find the solution for them, another gournd loop reappers !!!! I have put that aside for the moment, after trying an isolator for the subs (that did not work)...

 

But please - if you decide to try all of these - my word of wisdom is this: ensure that each time you manipulate any cable (AC, interconnect, usb), you turn OFF the volume and the power of each component. Not doing so may bring costly problems... And if a component has its earth lifted, be very careful... There can be a lot of current in these boxes - a lot more than you would expect...

 

Regards,

[beerandmusic]

ack....i didnt even think about it being something else plugged into outlet as computer is on....geesh, i can't discounnect everything...there must be 20 things plugged in....it's kind of my "office corner", 3 computers, 2 printers, monitors, phone, magicjack, lights, tons of stuff....yea, that's prob the problem...not the computer or ac in? something else causing the noise? yea, i don't want to try and figure that out...but for peace of mind, ii agree, i will run extension cable.

 

question...if i run extension cable to my pc and no more hum, is it still possible that something is wrong (ground with amp?) or i can rule that out, and rest in peace that there is no problems with my amp. that is my main concern since i just spent $600 on repairs of this $2500 amp.

 

going to go run an extension cable now....

[AlainGr]

Mmmm... I can tell I swore a lot when I did my investigation a couple of years ago. It's not for nothing that I dropped the prolem with the subs maybe it would be simpler for you to move the few components you wish to test in another room ? Not knowing how your are set, you can look for the simplest way to arrange this. Instead of disconnecting all (and I undersant this too), you could move yoru power amp, PC and speakers (I don't know if they are easy to move) in another room, on a different circuit...

 

I always try to get to the simplest solution... I am lazy

 

But remember for the sake of all the trouble it brings... Ensure that you have your system alone on a circuit, to narrow your search. Using cheaters and removing them one by one will help, but take notes

 

Boy, would I like to be able to make diagnostics from distance... But I can't. I am not saying you will find the solution in a few minutes. If it still does not help, to bring the components (or to invite the technician to come by)... Maybe one day it will be possible for one to appear in 3D and see all around what is going on...

 

Hey, hope this helps, but I feel the pain also... Do not get discouraged... Time and patience, even if it is very frustrating.

 

Just before I leave for the night: was this happening before you had your component repaired ? Has something changed in between ?

 

Regards,

[beerandmusic]

ACK!!

 

so i ran an extension cable from same outlet as amp, and still had hum...an interesting new development though...when i ran the ext cable to the pc, now my monitor has a wave thorugh it????!! ACK, UGHGH...!!!

 

so now i think the problem is something from the amp end?

 

the troubleshoooting continues....

[AlainGr]

Oops... Yes, there seems to be something odd happening... Could it be the electrical wall plate that has a problem ? Have you checked if there is a buzz at the electrical board (breaker) ? Sometimes things can get serious...

 

Have to leave for the night (work tomorrow)... If it gets overwhelming, maybe a technician or an electrician ?

 

But over all, be cautious ok ?

 

Regards,

[One and a half]

ack....i didnt even think about it being something else plugged into outlet as computer is on....geesh, i can't discounnect everything...there must be 20 things plugged in....it's kind of my "office corner", 3 computers, 2 printers, monitors, phone, magicjack, lights, tons of stuff....yea, that's prob the problem...not the computer or ac in? something else causing the noise? yea, i don't want to try and figure that out...but for peace of mind, ii agree, i will run extension cable.

 

question...if i run extension cable to my pc and no more hum, is it still possible that something is wrong (ground with amp?) or i can rule that out, and rest in peace that there is no problems with my amp. that is my main concern since i just spent $600 on repairs of this $2500 amp.

 

going to go run an extension cable now....

 

The Denon and many other HT receivers have a 2 prong IEC inlet, requiring no ground connection. The Macintosh amp would have a three prong inlet. If it plays ok other than the Dragonfly, the amp repair is OK. If there's nothing connected to the amp on the inputs and it still hums, then the repair is ineffective.

 

Since in a Hifi system, the amplifier is the conduit where all sound is controlled, it is the most logical place for a common ground to exist. When you connect the computer (and all the other gear), the path to ground must be a hell of a lot better with the Mac amp than the rest of the equipment, so all the hum goes through the amp connected by the interconnects from the source.

 

When you connect an iPhone, or the portable computer, their inputs float to ground, so there's not a problem.

 

A fix? Two choices

 

1.By the time you spend money on extenders, and the like, suggest to buy a small PC (like a mac mini/Nuc) plays music only, that uses a 2 prong power source and remote VNC with your LAN, and have the Dragonfly plug directly into the Macintosh with a short 3.5mm to RCA cable.

 

2. Buy an isolator from Jensen Transformers, it blocks the hum, but passes audio. CI-2Mini might just do the trick.

 

Here's a valuable resource on ground loops, it's not so simple to solve.

[AlainGr]

The Denon and many other HT receivers have a 2 prong IEC inlet, requiring no ground connection. The Macintosh amp would have a three prong inlet. If it plays ok other than the Dragonfly, the amp repair is OK. If there's nothing connected to the amp on the inputs and it still hums, then the repair is ineffective.

 

Since in a Hifi system, the amplifier is the conduit where all sound is controlled, it is the most logical place for a common ground to exist. When you connect the computer (and all the other gear), the path to ground must be a hell of a lot better with the Mac amp than the rest of the equipment, so all the hum goes through the amp connected by the interconnects from the source.

 

When you connect an iPhone, or the portable computer, their inputs float to ground, so there's not a problem.

 

A fix? Two choices

 

1.By the time you spend money on extenders, and the like, suggest to buy a small PC (like a mac mini/Nuc) plays music only, that uses a 2 prong power source and remote VNC with your LAN, and have the Dragonfly plug directly into the Macintosh with a short 3.5mm to RCA cable.

 

2. Buy an isolator from Jensen Transformers, it blocks the hum, but passes audio. CI-2Mini might just do the trick.

 

 

If was hoping your would come by

[tranz]

One other thing to try is an IFI USB Power. 2nd hand about $100. It filters USB ground, provides 5V and allows you to block (with tape ) the 5V and ground coming from the pc USB.

 

Another option is a Furman, APC or similar AC filter. Furman AC215A -$129, APC C2- $60. Don't think you can get any cheaper. I used a noise sniffer to check about a dozen different ones including much more expensive and these actually filter.

[speavler]

I had this same issue, and I was not about to put all that computer digital garbage onto the same circuit as my analog system. A usb/spdif (toslink) converter solved my issue.

[beerandmusic]

I had this same issue, and I was not about to put all that computer digital garbage onto the same circuit as my analog system. A usb/spdif (toslink) converter solved my issue.

 

this $2500 amp only has analog inputs and data ports (whatever those are)...no spdif

[beerandmusic]

at this point i am more concerned on what the problem is and how to fix it, rather than a bandage.

 

i want to know if the problem is with my old 1959 house wiring or the amp, since i just got it and paid $600 in repairs by authorized mcintosh repair servicer.

[beerandmusic]

The Denon and many other HT receivers have a 2 prong IEC inlet, requiring no ground connection. The Macintosh amp would have a three prong inlet. If it plays ok other than the Dragonfly, the amp repair is OK. If there's nothing connected to the amp on the inputs and it still hums, then the repair is ineffective.

 

Since in a Hifi system, the amplifier is the conduit where all sound is controlled, it is the most logical place for a common ground to exist. When you connect the computer (and all the other gear), the path to ground must be a hell of a lot better with the Mac amp than the rest of the equipment, so all the hum goes through the amp connected by the interconnects from the source.

 

When you connect an iPhone, or the portable computer, their inputs float to ground, so there's not a problem.

 

A fix? Two choices

 

1.By the time you spend money on extenders, and the like, suggest to buy a small PC (like a mac mini/Nuc) plays music only, that uses a 2 prong power source and remote VNC with your LAN, and have the Dragonfly plug directly into the Macintosh with a short 3.5mm to RCA cable.

 

2. Buy an isolator from Jensen Transformers, it blocks the hum, but passes audio. CI-2Mini might just do the trick.

 

Here's a valuable resource on ground loops, it's not so simple to solve.

 

thanks for all the info. i have found a short term resolution..., but more importantly is i want to know what the problem is..... is my problem the 1959 house wiring or some ground problem internal to the amp.

 

the short term resolution seems to remove the ground on the amp end (removing from the computer end didnt fix it).

so i am using one of those cheater adapters that removes the 3rd round ground plug from the stereo.

 

the issue therefore is whenever a ground from the receptacle to the amp is in place, i get the hum. if i remove the ground from the receptacle, the hum goes away.

 

1. so is the problem with my house wiring or open ground in the amp and how do i determine?

2. also, can this be bad or damage the amp by using one of these cheater plugs?

 

[jkenton]

Try this Ebtech - Audio Solutions. It's called HumX. It's a huge problem solver.

I have two in my complex system. I turned an audio buddy on to it who was at wits end and he was thrilled.

[AlainGr]

Hi again Beerandmusic,

 

Do you recall having that problem before you brought your power amp for repair ? Did you do something in between, like moving a few components on the same circuit ?

Does it also hum if you put it on a circuit where it is alone ?

 

As you have guessed, it is a matter of eliminating and narrowing the problem to its simplest.

 

If it still hums and it was not doing that before, maybe you should bring it to your technician ? I suppose he gives something like 30 days warranty or else ?

 

At least you will have the peace of mind if the problem is fixed for good...

 

Regards,

[beerandmusic]

this is the first time i am using with this amp. i didnt have the hum from the previous amp, but as "one and a half" pointed out the denon only has a 2 prong receptacle.

 

it pretty much is down to the simplest. with the 3rd prong used from the receptacle, it hums. without the 3rd prong, it doesn't hum. i just don't know if that means the problem is with the amp or with the house wiring.

 

short of trying another ma6500 amp, i don't know how to tell what is the problem...the house wiring or the amp.

[One and a half]

this is the first time i am using with this amp. i didnt have the hum from the previous amp, but as "one and a half" pointed out the denon only has a 2 prong receptacle.

 

it pretty much is down to the simplest. with the 3rd prong used from the receptacle, it hums. without the 3rd prong, it doesn't hum. i just don't know if that means the problem is with the amp or with the house wiring.

 

short of trying another ma6500 amp, i don't know how to tell what is the problem...the house wiring or the amp.

 

Neither the Mac amp or the house wiring is to blame. It's the interaction of wiring, the amp and the computer system that causes the problem. Yes, everything is supposed to work together, but in the real world it doesn't.

 

Here's a link that shows how a ground loop is formed. They usually appear somewhere else completely perhaps through a printer, or wall wart not even remotely used with the amp.

 

Finding the cause is to analyse the whole setup from the receptacle forward including to check how good the grounding system is in your house to begin with.

 

Systematically figuring out the paths of the signal wires, comparing them to the ground connected equipment, and even sometimes taking measurements. It's not simple, and without any drawings of what you have connected, these pages can go on for some time and by the end of it, we'll be shouting at each other, since this is a word only forum and not an interactive process. We need photos, drawings, voltage measurements, types of cables used to test the shield integrity, routing methods, proximity to other AC lines, SMPS, the list goes on.

 

We *could* try, but without all that above, we have no place to start. Pro help is available of course, get your electrician to check the receptacles first off. If you can find a control or instrumentation company, they could help you in finding the culprit.

[beerandmusic]

above you stated the mcintosh isn't the problem.

 

is it "possible" that the mcintosh is the problem? isn't it possible that there is a bad ground, loose wire, or something else internal to the amp that is causing the ground loop?

 

that really is my only concern.... i can go back to using the denon in this room, and then use a vivopc (mini pc with only 2 prong ac) with the macintosh in another room.

 

i just want to be certain there is no problem with the macintosh itself.

[One and a half]

above you stated the mcintosh isn't the problem.

 

is it "possible" that the mcintosh is the problem? isn't it possible that there is a bad ground, loose wire, or something else internal to the amp that is causing the ground loop?

 

that really is my only concern.... i can go back to using the denon in this room, and then use a vivopc (mini pc with only 2 prong ac) with the macintosh in another room.

 

i just want to be certain there is no problem with the macintosh itself.

 

From Post #11:

If there's nothing connected to the amp on the inputs and it still hums, then the repair is ineffective.

 

By which I mean nothing connected on the inputs, they are all disconnected. The only thing connected are the speakers and the power cable, nothing else.

[sandyk]

Are the computers in Standby Mode, despite not being switched on ?

[CR250]

Try lowering the volume controls on your phone, music software and OS. Use the volume on your integrated.