iFi Nanao hum

[ELOJR]

My iFi Nano has developed a constant low level hum. Has anyone else experienced this problem? Is it common for DAC's to have hum issues?

Thanks!

 

[antcollinet]

Is that hum from the actual dac - or from the speakers?

 

[ELOJR]

Good question. Not a "physical" hum. An electrical hum that I hera from my speakers. It goes away when I disconnect the cable from the DAC, so speaker amp is hum-less.

 

[ZolaIII]

And what's the power amplifier? Have you tried with another DAC?

 

[mansr]

Nothing within the iFi is remotely likely to produce hum. It's probably mains interference getting in somehow. The iFi could be definitely ruled out as the source (as opposed to a conduit) of the hum by feeding it from a laptop (or phone) running on battery.

 

[ELOJR]

Powered Kali LP6 V2 monitors. No amp needed. Plugging in another DAC is a great idea, but...I don't have another one

 

[antcollinet]

I'm guessing ground loop - what is the complete interconnect from mains to source to dac to amp? Which devices in the chain have an earthed mains supply (three pin plug). What is the length of any analogue interconnect?

 

[ELOJR]

Mac and speakers are three pin plug. Interconnects are three feet...well made cables.

My current monitors are relatively new...perhaps they are contributing to the problem. Although...I haven't noticed any hum with them before.

Hmmmm

 

[antcollinet]

Pretty certain that is a ground loop - especially if they are powered monitors. Do the monitors each have their own power connection? Or is one supplied from the other? Which cable are you disconnecting from the DAC to stop the hum?

If it is the two speaker interconnects, what happens if you touch the ground connection of the two wires together at the DAC end (after disconnecting from the DAC) does the hum come back?

Is your mac a laptop (can you try it battery powered?)
Or does it have an optical output you can connect to the DAC instead of USB?

 

[ZolaIII]

@ELOJR sure you have another DAC, probably bunch of them and probably not much behind mentioned iFi. Try with one in mac and one in phone if phone has analog output they won't give 2V out but it will work. Also try with another cable if you have one. Thing is I wouldn't rule out speakers at all as that whose a major problem with Kali's initial realise (V1). Actually really a major reason for V2 release where they supposedly improved the amplifier but never really explained how they did it. Anyway you need to try all mentioned (another DAC and cables) in order to rule out if it's one or other (DAC, ground loop or power amplifier) and diagnose the problem right.
Best regards.

 

[ELOJR]

Thanks much for the troubleshooting sessions.

My (new) iMac has just two Thunderbolt and two USB-C ports (no optical like my older one), and so my iFi is connected via USB.

But...based on your input, et me see what I can do to narrow the hum down.

 

[antcollinet]

It may well be the hum arrived with your new macbook - not due to the mac specifically** but due to different earthing arrangements.


**ground loop is a system issue, not a device issue.

 

[ELOJR]

OK...I did some troubleshooting.

* When there is no connection to the Kali RCA inputs, there's no hum.

* When the Kali's are connected directly to my desktop Mac or when they're connected with the iFi Nano in line, there's hum.

So...clearly a ground loop. I know from audio experience that ground loops can be notoriously hard to track down and eliminate.

Any suggestions?

(I don't recall this being an issue with my Tannoy Reveals and this Mac, but that doesn't help me now.)

 

[antcollinet]

Your speakers (as far as I can tell) have balanced inputs. By far your best solution would be to use a balanced source - if you can replace your nano with a balanced output dac that would almost certainly solve your issue.

If not, you're going to have to try to minimise the loop area. That is going to be tricky with powered speakers.


I'd start with connecting all powered and earthed devices back to the same power socket, keeping the power cables as close as possible together. Paradoxically also keeping the RCA cables close in together with the power. Your aim is to make the loop a narrow slot, rather than a wide circle.

 

[ELOJR]

Thanks, Tony. I'll try playing with the power cables and interconnects first.

Looking ahead...the DAC I'm considering has TRS outputs, in addition to RCA, and the Kali's have TRS inputs.

I know nothing about TRS. Would using those outs/ins do the same thing as going balanced?

Thanks!

 

[antcollinet]

If the TRS are balanced outputs (probably they are) then yes. Check the TRS inputs are balanced also. It is also possible to use a cable with TRS on one end and XLR on the other.

(TRS is just another 3 terminal connector - like XLR)

 

[ELOJR]

Are there pros/cons to using either TRS or XLR?

If not, then why offer both options?

 

[antcollinet]

No difference. I guess both are provided for compatibility with different sources.

 

[ELOJR]

Update: Thanks for the helpful responses to my questions. I replaced my iFi nano with a SMSL C200. I still had low level hum in the L/R monitors so I connected them via TRS cable (the iFi didn't have that option) and left the sub connected via RCA. Hum gone!