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Frank1938

Recent hum in stereo system

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Looking for some expert advice. A hum just appeared in my audio system in the family room. Stereo system has a 20 amp dedicated line which connects my Aragon Stage One, Aragon 2007, Direct TV and McIntosh integrated amp. I disconnected the cable box because that is usually the culprit. No hum when running the Aragon components and the TV or CD Player. It appears I have isolated it to my music distribution from my iMac to my McIntosh MA-352. On a different electrical line I am running USB out of the iMac to USB in on my Maverick DAC, RCA out of DAC to the McIntosh line one input (20 ft run). which is connected to the 20amp circuit. Connection worked perfectly until three days ago when the hum appeared. Tried different RCA cables from DAC to McIntosh to no avail. Replaced the power strip which connects the iMac and the DAC. Still have a hum. I have disconnected every device individually in the family room including the iMac and the DAC. Still have hum. Unplugged every item added for Christmas. No change.

If I switch inputs on the McIntosh 352 to CD (on the same 20 amp circuit as the McIntosh) input the hum disappears so it's not the new McIntosh. I would appreciate any opinion as to why this hum suddenly appeared. I'm baffled. Thanks in advance.

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I have a question for you
Do you have a tv near your system setup?
Why I’m asking this is that I had the very same problem about 2 years ago
I’ve had the 50” tv for two years and everything was great sound wise. Then one day I start hearing a bad noise problem
I already had a appointment with the cable company and when the tech showed up he was very impressed with my audio system and he heard the noise and he pulled out a handheld test gear and found out that my TV had no internal ground in it and it was producing the noise
this noise didn’t start up until I removed my audio system from the power grid the TV was on
I had ran a independent 20 amp breaker and outlet for the Stereo system
but the TV was not hooked up to the new outlet
So how he fix the problem for me was by using a grounded wallwart box that the Cable wire plugged into and then plugged into my TV to ground it
And no cable signal was running though the wallwart
everything still ran through all the HDMI cables
I will take a picture of this box and how it’s plugged in and see if this could help you
Good luck. I hope I’m on the same page as you are


Sent from my iPhone using Tapatalk

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Hi Carl, thanks for your reply. I actually have two systems, one for TV and one for two channel listening. I use the Aragon Stage One pre/pro and the Aragon 2007 seven channel solid state amplifier for TV. There is no hum with this system. I use the iMac USB out to the USB input on the DAC, RCA cables from the DAC to the McIntosh integraded amp. If I pull the RCA cables from the DAC, the hum goes away. I tried different RCA cables and still had the hum so I know it is not the cables. It's strange that I have used this setup for months since October when I got the new McIntosh. No problem. So everything was compatible. My Forte IIIs are used for both systems with a switch. Since the McIntosh only has RCA inputs I need to convert digital to analog through the DAC to listen to Amazon HD music or iTunes. I just don't understand why everything worked before for months until this week.

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8 hours ago, Frank1938 said:

It appears I have isolated it to my music distribution from my iMac to my McIntosh MA-352.

 

On a different electrical line I am running USB out of the iMac to USB in on my Maverick DAC, RCA out of DAC to the McIntosh line one input (20 ft run). which is connected to the 20amp circuit.

Two things here:  If DAC and iMac are on different electrical line, try putting them on the same line (as the amp I am assuming), try different combos of connection of amp/dac/imac. If the dac or imac have 3-prong plugs try using a ground cheater plug. Also try clearing any other wires from the 20 ft. RCA, wires on top of it or running along with it can introduce hum.

 

1 hour ago, Frank1938 said:

I use the iMac USB out to the USB input on the DAC, RCA cables from the DAC to the McIntosh integraded amp. If I pull the RCA cables from the DAC, the hum goes away. I tried different RCA cables and still had the hum so I know it is not the cables.

 

It's strange that I have used this setup for months since October when I got the new McIntosh. No problem. So everything was compatible. I just don't understand why everything worked before for months until this week.

And here: With everything hooked up, connected and turned on so you're hearing the hum, take a length of wire, bare at both ends, and start touching metal (chassis ground) of any two of the three offending components, easier with the amp and dac, harder with the imac, try any metal surface of the imac or you might have to take a cover off and access a circuit board ground. This method is safe as long as you only connect to grounds. Alligator clips help. This will show you if there is a weak ground connection between two components. (I wouldn't doubt the Ma352 has a ground connector).

 

And finally, from what you've said it sounds like the imac is the problem, specifically because the hum just came out of nowhere, I don't know how much control you have over drivers and sound settings with Apple but usb drivers, dac drivers, driver settings can cause hum. 

 

I would try things in the order I listed them. Hope this helps.

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Years ago, when I first connected my JubScala system (bi-amped, with two separate 2-channel (dual-mono) power amps, there was a severe hum and buzz problem.  This was because the power amps and sub were on a different circuit from the AVR, TV, Blu-ray player, etc., so I would not overload either circuit.

 

Naturally, the voltage varied by a volt or two between the circuits, which was enough to generate the noise.  The cure, after consulting with one of the more knowledgeable forum members (we’ve got quite a few on here), plus a couple of concert sound/pro audio guys, turned out to be grounding the two power amps, plus the AVR, and the turntable, all together, but NOT to the wall.

 

The T/T was already grounded to the AVR, so no worries there.  To connect the power amps to the common system ground, I still had some of the single-conductor automotive wire (in Green for Ground) left over from grounding the turntable to the receiver.  Unlike the receiver and the turntable, the amps had no grounding bolt, so the tidy way to do it was to attach either spade or ring terminations to the wire and loosen or remove a screw on the rear panel of each amp, then tighten it down with the termination firmly held under it.  No more hum or buzz!

 

Hope this helps.  Trying to get rid of noise like that can be really frustrating.

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Thanks to everyone who has offered advice. I have totally disconnected the iMac from the circuit but the hum is still there. With the DAC unplugged I still have a hum. I have reset the circuit breaker to the stereo system and the breaker to the iMac/Dac system. Connecting the McIntosh to the same circuit as the iMac and DAC didn't help. I'll keep investigating but I think a call to my electrician friend is upcoming. The RCA cables, when connected, seem to be causing the problem even separated from any electrical wiring as much as possible. Thanks again and best wishes for the holidays.

 

Frank

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Long RCA runs can do that pretty easily.  You said they're 20 feet long?  Are they shielded?  Not sure why they would all of a sudden cause an issue though.  Have you tried unplugging them and reversing each side with each other?

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No help, but had a hum in my Crown K1.  Got awesome help from the members and problem was solved. Good luck :D 

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16 hours ago, wuzzzer said:

Long RCA runs can do that pretty easily.  You said they're 20 feet long?  Are they shielded?  Not sure why they would all of a sudden cause an issue though.  Have you tried unplugging them and reversing each side with each other?

Thanks for responding. I tried everything, even putting in new cables. I bought them from Monoprice in October when I got the new McIntosh and they have worked fine. I don't understand why the issue just started either. I did install Sonos speakers in the dinning room but the issue is there even with them disconnected. I even tried moving the McIntosh to the same circuit as the iMac and DAC. No change.

Maybe my electrician friend will find the answer after Christmas. Thanks again.

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trying to get a grip here.... so with just your speakers, a Mac integrated amp and 20 foot long RCA cables plugged into it you have a hum?

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21 hours ago, babadono said:

trying to get a grip here.... so with just your speakers, a Mac integrated amp and 20 foot long RCA cables plugged into it you have a hum?

I responded to your post but I got a message that a moderator has to approve it. I don't know if there are any moderators active?

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42 minutes ago, Frank1938 said:

I responded to your post but I got a message that a moderator has to approve it.

 

I am guessing that you typed in and submitted your earlier reply (as a guest) instead of signing in to your account. 

 

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14 minutes ago, Khornukopia said:

 

I am guessing that you typed in and submitted your earlier reply (as a guest) instead of signing in to your account. 

 

I'm sure you are right. I didn't look to see if I was signed in. Thanks

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I think that I have isolated it to the DAC. I'm thinking that RCA connections on the DAC have lost their ground somehow. I found that an optical input also produces a hum. I bought an inexpensive Insignia optical/coax digital to analog converter at Best Buy, connected an optical cable from the iMac to the converter and used the same 20' RCA cables to connect to the McIntosh. No hum and it sounds pretty good. I wrote to Ryan at Maverick Audio explaining the problem but haven't heard from him yet. Thanks for asking.

 

Frank

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I see that both the Mac integrated and Maverick DAC have three prong power cords. Currently you are not using cheater plugs on either? And both are hooked up to an AC outlet where the grounds are for sure tied together?

Do you have a volt/ohm meter?

Sorry for my late and spotty replys, I´m on vacation in South America......

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So Frank1938 answered some of my questions in a PM. There are no cheater plugs(ground defeat) in the system currently and no reason not to think the grounds are tied together in his house wiring as they should be. If both pieces of equipment are grounded through the third prong of the power cord and their RCA jack shields are tied to the chassis this is a textbook case of a ground loop.

https://en.wikipedia.org/wiki/Ground_loop_(electricity)

So we need to do further troubleshooting to figure out how the two pieces of equipment handle the RCA jack shield connections. There are a lot of strange and incorrect ideas out there about what ground is and how it should be handled in un balanced equipment.

The first thing I would try Frank1938 is a cheater plug on one piece of equipment, say the DAC, to see if this the cause of the problem. The cheater should not be used as a permanent solution only a troubleshooting aid.

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