Allo BOSS DAC+RPi3+iPower = buzz/hum left channel

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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?
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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/accessory-groundhog/

Excerpt from support discussion:

> 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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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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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.
 
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/iFi-Groundhog-Ground-Control

There's an official thread for the kit:
https://www.computeraudiophile.com/...the-official-thread-launched-5th-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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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
 
Yes, I can try that this evening. But what will that accomplish? My TV does not have a 3-prong IEC plug on the end of its AC cable. What do you expect the HDMI connection to provide, exactly?
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Path to earth, but since your TV has 2-prong plug only ignore my suggestion.
I was just curious if IFI would be silent in that setup, as they advertise it.

Kind regards

Marko
 
I was wrong, my TV does have a 3-prong IEC AC plug. So I proceeded with the HDMI cable experiment. Unfortunately, with the iPower connected to the RPi3, connecting the HDMI cable from the RPi3 to the TV results in an awful hummmmmmm.

That's enough for me. I'm done experimenting. I think I'll spin some vinyl so I can relax.
 
I had the same problem (static sounding noise) using a raspberry pi with an Allo Boss when fed by an Ifi power... This sound was audible when being passed to my Firestone Audio Cute Beyond headphone amp and to my Audiolab 8000A amplifier. None of the equipment was earthed and the Ifi power was a 2-pin non grounded plug. Having tried various cables/power sockets etc. I returned the Ifi power as faulty and went back to my Anker Usb power supply - no noise and as far as I can tell the sound quality is just as good....
 
That's enough for me. I'm done experimenting.


Yep. Modern DIY-Audio - "Painting by numbers"

As soon as a little challenge pops up - you fail and run. :rolleyes:

Getting a clueless advise from Davey nicely supports that decision.

Why not trying to understand what you're doing first!?!?

Sometimes even measurement equipment helps! ;)

I'm running 3 iPowers and my amp without earth and without any issues.

Enjoy.


PS:
In 99% of all cases I've been experiencing hum it had to do with a broken cable or
a poor connector/connection.
Make sure you have a nice starground in place.
Usually TVs build awful groundloops. TVs connect to the network (ether/cable/antenna/....) and more. The only way I'd connect a TV to a stereo would be via Toslink.
 
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Yep. Modern DIY-Audio - "Painting by numbers"

As soon as a little challenge pops up - you fail and run. :rolleyes:

Getting a clueless advise from Davey nicely supports that decision.

Haha. :)

I admit to being puzzled by the situation, but I don't think the advice was "clueless."

Based on his communication with iFi, their assessment of the issue seems to be the iPower is not working correctly because of lack of (earth) ground. Yet their unit does not have any capability/facility to connect an earth ground.....that I can see. It's up to the user to facilitate this ground connection elsewhere in their system, I guess. There are myriad different systems this unit might find usage in. Lots of variables and places for things to go wrong. :)

Your advice seems to be to check all interconnects and other connections and that will fix the problem. That may or may not solve the situation, but it doesn't give me a good feeling about the engineering of the iFpower scheme if this type of minor detail completely spoils the performance of their unit.

Cheers,

Dave.
 
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Swapping out interconnects for known-working ones did not change anything. I wish it had.

I also rigged up an RCA plug with the ground terminal only connected, into an RCA dual-F to single-M Y-adapter, plugged into the Left Out of the BOSS DAC. I then connected the bare signal ground wire from there to the earth terminal on an IEC AC outlet (presumably connected to mains earth). The buzz did not change at all, not one bit. It stayed exactly the same.

The buzz may be due to a fault in my home's wiring, for all I know. I live in an apartment building, so I'd have to complain to management to get anything done about that. The house rules are that I'm not permitted to mess with the wiring on my own, or to hire someone to do that for me.

In the iPower's defense, it is a nicely finished product, comes with high-quality adapters to facilitate connection to all manner of devices, and did provide a noticeable improvement in sound quality to the playback from my Pi+DAC.

At any rate, I gave it a try, sorry it didn't work out. I have a working setup that doesn't buzz, so I'm moving on now...
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Troubleshooting performed on this problem:

As mentioned previously,

Swapping out interconnects for known-working ones did not change anything. I wish it had.

I also rigged up an RCA plug with the ground terminal only connected, into an RCA dual-F to single-M Y-adapter, plugged into the Left Out of the BOSS DAC. I then connected the bare signal ground wire from there to the earth terminal on an IEC AC outlet (presumably connected to mains earth). The buzz did not change at all, not one bit. It stayed exactly the same.

Also, I went through the ground connections in my O2 headphone amp, after reading that this was sometimes a problem. I reheated any suspect solder connections on the O2 pcb, just to make sure. One curious thing about this was when I put pressure on the Line In jack on the O2, I could get the buzz to stop. But since the amp uses one of those plastic-enclosed 3.5mm 3-conductor PC-mount jacks, I didn't have an easy way of testing to see what that was doing. I could have persevered, but I really did not want to risk breaking the only headphone amp I have. I hate desoldering those PC-mount, multi-pin jacks.

When it became clear that fixing the buzz would have required some serious troubleshooting of the apartment building's wiring, I decided I'd better give up. I have three working audio systems that don't hum/buzz (including the big one with the phonograph), so I figure I'm OK enough for a clueless hobbyist.
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In 99% of all cases I've been experiencing hum it had to do with a broken cable or
a poor connector/connection.
Make sure you have a nice starground in place.

BINGO!

I think I've found the answer. From O2 Mistakes

Don't forget the wire you have to solder onto the middle front (ground) terminal on the input jack and wrap around the nearest case cover screw. This single point ground puts the case at the same potential (voltage with respect to earth ground) as the PC board ground, which helps eliminate sources of noise and hum.

Ah ha! Those instructions were not included with the original build guide for the O2. I don't think I have a wire going from the ground pad on the pcb to a screw going into the case. I'll try that this evening, see if it makes a difference.

Thanks to agdr for compiling that O2 troubleshooting guide. Very helpful!

Too bad I gave up too soon and sent back the iPower. If this turns out to be the source of the problem, I'll wait for the refund and buy another one, try again. The setup did sound very good indeed when powered by the iPower (except for the buzz, of course).

I feel pretty stupid, actually. Of course the pcb ground would need to be connected to the aluminum chassis! Duh.
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