Horrific distortion when using DAC, Yamaha Receiver, & iMac

[m021478]

I have a pair of Polk OWM5 speakers connected to a Yamaha RX-V667 Receiver, which is then connected to my ARCAM rDAC, which is then connected to my new 27" iMac.

 

90% of the time when I try playing audio out of my iMac after the computer has been sitting idle for a while, the audio will start to play back normally for about 1-3 seconds, and then it quickly starts to get crunchy/staticy... the noise typically heard at a McDonald's drive-through window.

 

If I switch the audio output source on my iMac to any other source (such as the internal speakers), and then immediately switch back to my DAC, it resolves the problem and I can then play audio normally for an extended amount of time. The same problem was also happening with the DAC I just upgraded from, the AudioEngine D1.

 

I'm kind of at a loss here and I was hoping someone could help me shed some light on what the problem might be. Any suggestions would be greatly appreciated... Thanks!

[m021478]

This issue is absolutely killing me, and I'd be beyond grateful if someone could chime in with some words of wisdom. Thanks!

[Paul R]

You might try loading a disk with a fresh copy of Mac OS, and booting from that. If you still have the problem with a fresh copy of Mac OS, then there's most likely a hardware problem.

 

If you don't have the problem, then there is most likely a hunk of software loaded on your Mac that is fighting for control of the audio.

 

I would guess it is going to be a software conflict, given your description if the problem.

 

Hope that helps a bit.

 

Paul

 

 

This issue is absolutely killing me, and I'd be beyond grateful if someone could chime in with some words of wisdom. Thanks!

[Melvin]

A bit more info might be helpful. For example, what player software are you using (iTunes, Audirvana, etc.)?

 

If, say, you are using Audirvana then your Audio MIDI settings should be set to Built-in Output and you would select your DAC in Audirvana's preferences. I believe it's the same for BitPerfect and Pure Music as well.

 

I've had a similar nasty noise (awful isn't it!) when playing the latest version of Pure Music. I restarted my Mac and it righted the offense.

[avta]

Just as a guess I'd check your wires. Should we assume you're using usb out to your dac then standard rca from the dac to your Yamaha?

[m021478]

I am using iTunes for playback, but the noise distortion I am experiencing is happening all over the place (i.e. when I playback a youtube video, in quicktime, when using quicklook, etc).

 

I do have my DAC connect to my computer via USB, and I am using standard RCA from the DAC to the receiver.

[avta]

So if you listen through the computer's speakers or headphones the distortion is the same?

[m021478]

no... problem doesn't happen when listening through my computer speakers or with headphones.

 

I think the problem might have something to do with a Ground Loop Isolator (Amazon.com: Stinger SGN20 Ground Loop Isolator: Electronics) I added to my setup to alleviate a white noise hiss that was coming out of my speakers for one reason or another. The ground loop isolator immediately eliminated all white noise, but it seems it might have something to do with my current issue. To early to confirm for sure, but I changed the location of the Ground Loop Isolator in the chain of connections and so far I haven't had the horrific distortion that prompted me to create this thread.

 

I previously had it installed in between my receiver and the rca cables, and I moved it so that it's now installed in between the rca cables and my DAC.

 

Who knows? So many variables involved that it makes one's head spin.

[Melvin]

Seems you've made some progress at least. Hope that's all it was.

[m021478]

I thought I'd resolved this problem, but I was wrong. It came back, and hasn't gone away since!

 

Could it have something to do with the AC circuitry that my receiver/speakers/computer is connected to? If so, anyone have any suggestions on what to do?

 

Any suggestions would be greatly appreciated... Thanks!

[mayhem13]

The fact that it repeated with two seperate USB DACs suggests the problem is on the Mac side, whether its hardware, supply voltage or software I'm not sure. It may be an electrical issue where there's no neutral path on the supply side. Try plugging in the iMac to an outlet that's on a different circuit than the one it's currently connected to. You can also try a ground lift plug that will isolate the mains ground.

[m021478]

The fact that it repeated with two seperate USB DACs suggests the problem is on the Mac side, whether its hardware, supply voltage or software I'm not sure.

In an attempt to narrow down the source of the problem, I placed my laptop right on the counter top next to the receiver, then I connected a short stereo audio cable from the Yamaha receiver to my Arcam rDAC (also on the counter top), then a .5m Pangea Audio USB cable from the DAC to my laptop (plugged in, as well as running on battery) and sure enough, the problem persisted and I still got the distortion issue!

 

Any ideas?

[mayhem13]

Ok so the battery use eliminates an EMi/EFi problem from the Mac. Does it do this in every USB port on the Mac?

 

.....I'm confused....iMac or MacBook?.....or both?.....since you mentioned iMac in the opener, then laptop and battery in reply.

[m021478]

Ok so the battery use eliminates an EMi/EFi problem from the Mac. Does it do this in every USB port on the Mac?

 

.....I'm confused....iMac or MacBook?.....or both?.....since you mentioned iMac in the opener, then laptop and battery in reply.

I exclusively play music via my iMac, but in an attempt to narrow down what the problem might be, I connected my Macbook to the DAC/Receiver/Speakers instead to see if that resolved the problem. It didn't.

 

I am pretty sure the issue has something to do with the Stinger SGN20 Ground Loop Isolator I added to my system in an attempt to subdue some really bad white noise/hissing coming from my speakers. I'd rather not have to use the ground loop isolator, but the amount of noise and interference I was getting before adding it into the mix was unacceptable. Based on advice from people on threads such as this one, this one, or this one, a ground loop isolator seemed like a possible solution.

 

Interestingly, the first Amazon customer review for the aforementioned Stinger ground loop isolator says,

"This was used between a TV and audio system that were on opposite sides of the room and significantly violated all grounding rules. Without some isolation the line noise was very bad."

Well, whatever grounding rules he's talking about, my computer and DAC are on the opposite side of the room from my Receiver and speakers. Might this have something to do with my problem?

 

What causes the white-noise and hissing that lead me to add the ground loop isolator to the mix in the first place? Is there a better was to go about dealing with it then through the use of a ground loop isolator? I wonder if connecting all of my A/V components to a Panamax M4300-PM 9 Outlet Clean Power Level 2 would help? I assume it has something to do with dirty AC currents, but that's just a guess, though I don't know a thing about AC circuitry... my assumption is based on other threads I've come across like this one, this one, and this one.

 

I'm at a total loss here and I could really use some help with this. Any ideas? Thanks!

[mayhem13]

Ok, so it does it with two different computers, two different DACs, both via USB using the same Yamaha receiver?

 

Your DAC has an optical input and both your iMac and Macbook have optical outputs via the headphone jack using a mini optical adapter/cable. Have you tried it with an Optical connection?

[One and a half]

What gain have you got on the audio out for the RDac?

 

Usually this is fixed at 0db, hopefully greyed out in audio Midi and iTunes is also set to 0db. Volume adjustment is completed by the Yamaha. ITunes doesn't use exclusive mode Hog mode, so uses shared resources.

That's one thing to fine tune later.

 

Since the noise you are getting is from the laptop as well as the iMac, it's the interaction from the Arcam rDac's uSB and the Yamaha receiver analog inputs.

 

On the end of the Yamaha, please state if three prong or two pin prong AC plug is fitted. I see the ARCAM rDAC has a wall wart 6V power supply. From the manual for the rDAC the power supply is two prong, that's the problem. Noise from the AC mains is free to flourish from the computer to the RDac, since there is no real ground to tie anything to. Sometimes the neutral connection causes a problem, can you reverse the orientation of the rDac's wall wart?

 

You mentioned that you have the Panamax M4300, I guess the Yamaha is connected there, what about the Arcam, is it plugged into the same place? Since the Mac is some distance it most likely will be plugged into the wall with different earth potentials to the rest of your system, that's a problem but can get around that. Another issue is how long is the USB cable from the ArCam to the iMac? Or are you transmitting across the room with analog? Details pls, important.

 

The Audioengine used the 5V from the computer for power, so the noise from the computer still manages to find it's way to the Yamaha and make a mess.

 

Ideally all electrical components should go into the Panamax, but am concerned about the distance to the iMac with running a long AC cable together with USB or analog along the same route.

 

Ideally the rDAC would have a 6V power supply with a mickey mouse cord, a look after 6 pages on Amazon didn't find one. This will tie the internals of the power supply to earth, same as the Yamaha, so reducing the shield voltage on the interconnect between the Yamaha and the rDac. A 'better' priced interconnect may help, but no guarantees.

 

The cheapest way out of this is to:

- Use a USB extender (Ranger) from the iMac across the room with Ethernet cable between the USB receiver and transmitter.

- Use an iUSB between the USB extender receiver and rDac USB input $300

- Find a 6V 600mA-1000mA DC power supply with a three prong AC cable for the RDac ~<$80 -$400 (lab precision)

- Plug Yamaha, iUSB, new 6V supply, USB receiver into the Panamax.

 

 

Next up in price to fix

- Replace the rDAC with say a Mytek $1600, TEAC UD-501 or any DAC really with a three prong AC cable

No guarantees about getting rid of the noise "completely", will be reduced though

 

Ultimate Solution

- Keep the gear what you have, still get the extender

- Get a Furman IT Symmetrical Power supply to replace the Panamax, $3500 or an Equitech 1-2kVA model a little cheaper but over the price for the Mytek.

 

This will remove the noise.

[mayhem13]

Really?.......spend $3500 to get rid of an intermittent distortion/error? If its really something in the household electrical more likely it would be consistent as a wiring error isn't an intermittend, and of it is, better to spend that $$$ on a certified electrician before someone gets hurt.....or worse!

 

But seriously, the troubleshooting chain hasn't reach either end yet. There's no way of diagnosing this an electrical issue just yet.

[One and a half]

Oh! You have a better price for the Furman! It's the only symmetrical AC solution they have. I did offer an alternative.

 

The OP's dilemma is markedly similar to Flac to Dac's issue with a two prong supply to a DAC causing noise, when the chain is C.A.M.S. (PC Server) --> DAC --> Receiver/amp.

 

Anyway, noise is getting in somewhere the shielded cables blot out the noise sometimes, until the shield voltages start to increase between the receiver and the DAC. This can occur if the line voltage increases giving you that extra volts to overcome internal parasitic capacitative impedances, especially in the wall wart supply. Seriously.

[mayhem13]

Wouldn't spend that much on any power conditioner..........i got my lab grade units for pennies on the dollar!

 

I'm just not convinced this is an AC mains problem and if it is and so severe, repair the wiring instead for less money and live longer.....and safer. Not the audiophile approach, but a rational approach, no?