1 Topic by Crunchynut (edited by Crunchynut 2022-12-24 00:02:46)

  • Registered: 2022-01-08
  • Posts: 26

Topic: ADI-2 DAC FS - Crackle on 1 channel until warm - could it be the DAC?

Apple Music > iPad 6 15.6.1 > Apple USB-C Digital AV Multiport Adapter > 4 metre usb A to B > ADI-2 DAC Fs v51 > QED Reference Audio 40 Phono to phono interconnects > Musical Fidelity M3Si integrated amplifier in power-amp mode > 2 metres per channel of QED Original speaker cables> Focal Kanta no 1 speakers

Hi all,
My hi-fi set-up has been installed and in use for a good few months with no problems and great sound. The amp and speakers can also take input from my TV system.

In the last couple of days, after watching TV for some time, meaning the amp and speakers are warm, I have changed to listening to my hi fi. This has involved switching the DAC on and the amp over to direct input (so the DAC is the pre-amp and just the amp power-amp circuitry is used). I have then noticed a crackle on the right channel, which isn’t very loud but clearly a problem. However it clears after about 10 minutes. To test to see if the iPad /USB source is the problem, whilst the crackle is evident on the line-out to amp and speakers, I have plugged in my headphones to find there is no crackle from the DAC headphone output. So it seems it might be a fault with the DAC line out circuitry until, perhaps, the DAC warms up.

I need to do some more elimination tests, but wondered if these symptoms struck a chord with anybody?

2 Reply by KaiS (edited by KaiS 2022-12-24 00:36:11)

  • KaiS
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  • Registered: 2020-02-05
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Re: ADI-2 DAC FS - Crackle on 1 channel until warm - could it be the DAC?

Systematic fault isolation checks:

1. Reverse the RCA (“phono”) connection L<>R at ADI-2’s side only.
If the crackle now appears at the left speaker, ADI-2 is the cause, -> 4.

2. If crackle is still on the right side, reverse the RCA’s on the amp side.
If the crackle now appears at the left speaker, the formerly right cable is the cause.

If the crackle disappeared in step 1. or 2., it was just a dirty RCA connector.

3. If crackle is still on the right side, use a different, known good amp input.
If the crackle disappeared, the amp’s input is defective.


4. To double check / verify ADI-2 is the cause:
If you have adapter cables to temporarily connect your headphones to ADI-2’s RCA (“phono”) line outputs - the same that you use for your amp - you can verify if ADI-2 is the problem.
Don’t possibly worry, ADI-2’s line output can drive headphones without breaking, it’s protected against short circuit.

For those wondering:
No, this is not suggested as normal use case, as the line output’s impedance of 100 Ohm changes the sound of most headphones, although drive power would be sufficient in most cases.

KaiS's Website

3 Reply by Crunchynut (edited by Crunchynut 2022-12-24 17:38:14)

  • Registered: 2022-01-08
  • Posts: 26

Re: ADI-2 DAC FS - Crackle on 1 channel until warm - could it be the DAC?

Thanks for the reply. Step 1 is exactly as I intended.

So, I have reversed the phono interconnect leads - meaning the right DAC output now feeds the left phono interconnect, amp channel and speaker, and visa-versa.

Result : no crackle anywhere! So, maybe, it was just a dodgy phono lead connection. But I can’t imagine why this would ‘warm up’ and resolve itself after 10 minutes.

The only other change is that I moved the DAC whilst swapping the interconnect and hence the Power Supply lead will have been strained - could have been a loose power connector, maybe? But then the Locking connector should guard against this and I can’t think why this would affect only one channel.

I will listen in this switched mode for a few days and see if the fault reoccurs.

4 Reply by KaiS (edited by KaiS 2022-12-24 19:03:06)

  • KaiS
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Re: ADI-2 DAC FS - Crackle on 1 channel until warm - could it be the DAC?

Crunchynut wrote:

Thanks for the reply. Step 1 is exactly as I intended.

So, I have reversed the phono interconnect leads - meaning the right DAC output now feeds the left phono interconnect, amp channel and speaker, and visa-versa.

Result : no crackle anywhere! So, maybe, it was just a dodgy phono lead connection. But I can’t imagine why this would ‘warm up’ and resolve itself after 10 minutes.

The only other change is that I moved the DAC whilst swapping the interconnect and hence the Power Supply lead will have been strained - could have been a loose power connector, maybe? But then the Locking connector should guard against this and I can’t think why this would affect only one channel.

I will listen in this switched mode for a few days and see if the fault reoccurs.

You can switch back to “normal”, the crackle probably won’t reappear as the dirt in the connector now is gone.

Disappearing of such phenomena after some play time is quite typical for bad contacting of all kind, dry-wiping Jack- and RCA- connectors before plugging is a common practice in the recording studio to avoid such.

Sprays are an effective hardcore solution for a momentary improvement, later the connectors collect even more dirt, so avoid these.
Clean gold-plated connectors is the way to go.

KaiS's Website

5 Reply by Crunchynut (edited by Crunchynut 2022-12-27 14:49:48)

  • Registered: 2022-01-08
  • Posts: 26

Re: ADI-2 DAC FS - Crackle on 1 channel until warm - could it be the DAC?

I have now switched back to correct left and right channels and the problem appears not to have re-surfaced. So, it looks like it was just a dirty interconnect. Strange - since they are gold plated screw-in locking types, so it’s difficult to understand how dirt or oxidation could have got into the contact area. But it’s the only explanation at the moment.
I’m glad it wasn’t the RME - wouldn’t want to spoil its perfect reputation in my use so far.

Thanks for your input @KaiS