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RE: A week with the iFi Micro iDSD

Posted by Thorsten (M) on November 20, 2014 at 11:38:06

In Reply to: RE: A week with the iFi Micro iDSD posted by Sprezza Tura on November 20, 2014 at 10:59:48:

Hi,

> To clarify, when I used it on the desktop I was using it with a
> MAC/Audirvana combo. Drivers not an issue.

MAC/Audirvana is limited to using the DoP protocol for DSD. The problems with pops and clicks when changing from DSD to PCM or reverse with DoP are well documented and not specific to iFi products.

In fact only products that use a DAC Chip that not only auto-selects between PCM and DSD material but internally converts DSD to (a form of) PCM are reliably free from this problem, as they in effect never actually change from PCM to DSD.

> -"Wake Up Pop" occurs even when volume control all the way down.

Of course.

I was referring to the gain AFTER the iDSD (Amplifier/Active Speaker), both in order to get the correct volume control range and a normal (quiet) level of pop during enter/exit power save.

You will find that if you turn the gain controls on your active speakers / amplifiers down enough to have a sensible volume control range the standby clicks are much reduced.

As said, both the problems with tacking at low volume and the loud clicks are a direct result of excessive gain AFTER the iDSD micro, Just turn things down and there is no substantive problem.

> I am using it in hub power mode, so I am not even sure why there
> would be battery circuit engaged.

Power save is applied in USB power mode after 15 minutes without signal. The reason is that standard USB ports (at 500mA maximum current) lack sufficient power to power the iDSD micro in normal and turbo mode. Especially Turbo mode will eventually deplete the battery even without signal on standard 500mA USB ports.

Hence the iDSD micro will switch off the DAC, analogue stages and headphone amplifier (which account for most of the power consumed) when no music is playing to allow the battery charger to charge the battery if needed.

Like the iDSD nano, the iDSD micro is in effect always on "Battery Power".

> -I got one thing wrong..it was in FIXED mode that the DSD/PCM pop
> would occur, and this was with a SOtM mini server, again no drivers
> required. I did not notice it on desk top.

The pop will happen if the playback software does not gracefully exit DSD playback but stops DSD playback via DoP hard. Fixed or variable has nothing to do with it.

It is a fundamental weakness of the DoP protocol combined with DSD.

If you had applied the Version 4.06 Firmware revision to the iDSD micro you may have found the problem much less noticeable. The 4.06 Version of the firmware has been out since September.

> -To address your other notes, I do not believe it is a system issue
> for the following reason.

It is a system issue.

> I was sufficiently impressed with the Micro that I purchased a Nano,
> which I just got. Channel tracking is perfect, even at low volumes.

The nano uses an electronic stepped attenuator controlled by the microprocessor. The potentiometer in the nano controls this electronic attenuator indirectly via an AD converter that reads out the position of the potentiometer. So tracking is as perfect as this stepped attenuator allows.

The micro uses the potentiometer directly to control the audio signal.

We feel that the iDSD nano attenuator/output chip offers high sonic quality, however it is not we feel as good as using the potentiometer directly for audio, as it is done in the micro.

> Secondly, there is no wake up pop on the Nano.

Because the nano has a much smaller battery and a much lower power consumption, so it happily lives on a 500mA USB Port and has plenty of power left for charging in this case. So there is no "sleep" mode and no wakeup.

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

Edits: 11/20/14

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