Allo BOSS DAC+RPi3+iPower = buzz/hum left channel - diyAudio
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Old 17th June 2017, 02:50 PM   #1
rongon is offline rongon  United States
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Default Allo BOSS DAC+RPi3+iPower = buzz/hum left channel

I've reached out to the mfg's for help, awaiting replies from some. Now I'm reaching out to all you smart people in the forums. I hope somebody can help.

I'm running Moode 3.7 on a RPi3 with Allo BOSS DAC and iFi iPower 5V.

When there's no track playing, I hear a ratty hum/buzz in the left channel only. It sounds like a ground loop, but goes away once the music starts playing. (I know, you're thinking the music is masking the noise. But, if the music track starts with near silence, I can hear the buzz disappear.)

This buzz is heard from the RPi3 whether it's running into my Objective 2 headphone amp or into my living room stereo.

If I place my hand on the Objective 2 headphone amp, the buzz gets noticeably louder, even with music playing. (Aha! A lifted ground somewhere? Well, I opened up the O2 to test for lifted grounds and could find none. I reheated the solder joints, just to be sure. Nothing changed, no improvement.)

If I substitute in a cheapie Behringer UCA202 USB sound card to play from the RPi3 the buzz/hum is still there. However, this is still with the BOSS DAC HAT installed on the RPi, and with the iPower for power.

If I take the last setup (Behringer UCA202 USB soundcard as the DAC) and use the Canakit 5V adapter instead of the iPower, the buzz is now completely gone.

If I go back to the BOSS DAC but with Canakit 5V adapter, once again there is no buzz at all. So....

What would you suspect is the problem? The iPower?
--

Last edited by rongon; 17th June 2017 at 03:00 PM.
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Old 17th June 2017, 03:48 PM   #2
Davey is offline Davey  United States
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It seems obvious your iFi unit is the problem. Set it aside, use your Canakit adapter and enjoy the music.

Dave.
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Old 17th June 2017, 04:26 PM   #3
rongon is offline rongon  United States
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Thanks Davey. Unfortunately, the music sounds noticeably better with the iPower supplying the DC. I guess it's going back to Amazon, unless another solution presents itself...
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Old 17th June 2017, 04:47 PM   #4
Davey is offline Davey  United States
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Quote:
Originally Posted by rongon View Post
Thanks Davey. Unfortunately, the music sounds noticeably better with the iPower supplying the DC.
Yeah, except for all the noise.

Well, you either have a defective unit, or all the iFi blurb about ANC+...ultra low noise...etc, etc, is just BS. It is a switching unit after all and inherent noise is a given.

Dave.
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Old 17th June 2017, 08:57 PM   #5
rongon is offline rongon  United States
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iFi tech support says my system has no ground, and that is why the ultra-low-noise iPower is buzzing. I guess it's ultra-low-noiseness is why it's bothered by the lack of a ground, while the Canakit SMPS isn't bothered by it (???).

I'm not sure I'm buying that explanation. Why on earth would a super-duper-more-better power supply hum if there's not a ground, while a mediocre power supply would *not* hum? Man, I can't wrap my feeble mind around that one.

They assure me there is no ground in my system, and that I need to buy this to fix it:
http://ifi-audio.com/portfolio-view/...ory-groundhog/

Excerpt from support discussion:

Quote:
> I would be inclined to believe that my system is missing a ground if it hummed with
> other devices connected instead of the iPower. However, and I want to make this
> clear, the system only hums if the iPower is being used as the power source for my
> Raspberry Pi. If I use the original Canakit 5V SMPS, there is no hum. Why would that
> be?

- The iPower requires an earth / ground in the system as it has an extremely low noise floor and also requires earth to drain the excess within the system.
Wow. I don't get it. The iPower has an extremely low noise floor so it requires a ground (earth) connection, whereas other, noisier power supplies do not require a ground connection. What?
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Last edited by rongon; 17th June 2017 at 09:02 PM.
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Old 18th June 2017, 04:56 AM   #6
Davey is offline Davey  United States
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I can assure you they're full of it and are just looking to sell you more gadgets.

The photographs of the iPower show no earth connection (I see two prongs only), so I'm not sure how they expect an earth connection. Bluetooth? Magic?

I suggest to cut your losses.

Dave.
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Old 18th June 2017, 05:13 AM   #7
mkusan is offline mkusan  Croatia
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Quote:
Originally Posted by Davey View Post

The photographs of the iPower show no earth connection (I see two prongs only), so I'm not sure how they expect an earth connection. Bluetooth? Magic?



Dave.
Via another component in his system which is earthed. Is there such a device in your system?

Kind regards

Marko
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Old 18th June 2017, 01:39 PM   #8
Davey is offline Davey  United States
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Originally Posted by mkusan View Post
Via another component in his system which is earthed. Is there such a device in your system?

Kind regards

Marko
Yeah, but how would such an earth connection reference to the iFi unit which only has a 5VDC/ground connection to the rest of his system?
That suggestion/requirement implies that the iFipower unit expects some type of earth ground connection from elsewhere in the system to carry onto the ground side of whatever component the iFi is powering for it to work correctly. Do you think that would normally be the case in most audio systems?

Dave.
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Old 19th June 2017, 02:32 PM   #9
rongon is offline rongon  United States
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I've tested this on three different setups, including the simplest setup there could possibly be: The Raspberry Pi 3 with BOSS DAC and iPower plugged into an Objective 2 headphone amp which was running on DC battery power (two 9V batteries mounted internally).

In this particular setup, the one and only connection to AC was through the iPower. Unfortunately, that setup has a real bzzzzzz problem.

As Davey pointed out, it looks like the iPower needs the ground connection to mains earth that would be supplied via a 3-prong IEC connector. However, the iPower does not come with that connector. You have to purchase its equivalent separately in a $49 cable kit they call the Groundhog:
https://www.musicdirect.com/store/iF...Ground-Control

There's an official thread for the kit:
https://www.computeraudiophile.com/f...h-of-may-2017/

I don't have time in my life for a power supply that introduces a buzz even into such a simple DC-powered setup, and especially when my RPi3 came with a power supply that works without introducing any buzz at all, in any setup in which I've tried it.
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Old 19th June 2017, 03:18 PM   #10
mkusan is offline mkusan  Croatia
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Quote:
Originally Posted by rongon View Post
I don't have time in my life for a power supply that introduces a buzz even into such a simple DC-powered setup, and especially when my RPi3 came with a power supply that works without introducing any buzz at all, in any setup in which I've tried it.
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It is a valid decision, but can you repeat your test one more time with HDMI cable connected between RPI and TV and post back the result please?

Kind regards

Marko
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