[Lol999]

Hi, can someone please explain the difference between the two please? I understand that the Kali re-clocker works with the piano dac and others that are slaves, yet will not do so with the Iquadio pi-dac pro that I have on order.
In the absence of any meaningful information does that mean the the Pi-Dac pro has its own clocking mechanism to reduce jitter etc?
When I have bought standalone dacs the handling of jitter and clocking has been something the sellers have been often keen to emphasise yet I can't find it mentioned in any of the HAT dac literature.

Can anyone explain this one to me please?

[JohnR]

I2S is a set of clocks and a data signal. This is different (somewhat) to SPDIF. So don't compare I2S DACs (as all RPi HATs are) to normal DACs, it will just confuse you.

"Master" and "slave" refer to who generates the clocks. If the (I2S) DAC is slave, then the clocks are generated by the source device (in this case, the RPi) together with the data:

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Clocks: Source device -> Slave DAC
Data:   Source device -> Slave DAC

The problem with the clocks generated by the Raspberry Pi is that they are generated by dividing the processor master clock, which is not an exact division, so the clocks get jittery. So the Allo Kali is one solution, which reclocks (retimes) the clocks and data signals between the RPi and the DAC.

The other way to get a better clock is to have the DAC do it i.e. have the DAC be the clock master. This requires different drivers in the RPi software. So, the DAC generates the clocks, and the source device (Rpi in this case) has to generate the data "in time" with those clocks:

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Clocks: Source device <- Master DAC
Data:   Source  device -> Master DAC

Some DACs (e.g. Sabre) have their own internal reclocking so probably benefit less from either of the above approaches.
 

[JohnR]

BTW I don't see any crystals on the Pi-Dac pro so I'm not sure that it operates as a master. Perhaps there's some other incompatibility?

[Lol999]

well I'll be installing it later so we'll see what happens!