Post by MartinT on Feb 18, 2019 12:02:00 GMT
The Allo Kali is an interesting plug-in card, designed to mitigate the Pi's inadequacies in the I2S department when generating audio output.
As some of you know, the Pi makes for an excellent audio streamer, having sufficient performance, low power requirements and small size to suit the job well. There are also several software builds to make a streamer from a Pi such that you can pick your flavour to suit. Furthermore, if you use a plug-in DAC then you have a nice all-in-one solution.
However, many people want to use an external DAC for even higher performance and that tends to fall into three camps: USB, S/PDIF and I2S. If you want the best S/PDIF feed available, there are only two choices: the Allo DigiOne or DigiOne Signature. The equivalent for I2S (although not a complete solution in itself) is the Allo Kali.
What the Kali does is to ignore the inaccurate timing of the signal derived by the Pi itself and generate a highly accurate one. The Pi has only a single crystal clock whereas the Kali has two: one for 44.1kHz and its derivatives (such as 88.2kHz) and the other for 48kHz and its derivatives (such as 96kHz). These plus the very low jitter and dedicate power supply routing dish out signals with only 4ps of jitter, ideal for a high end DAC.
The board itself has a handful of LEDs to help diagnose your setup which I have found very useful. They tell you the incoming sample rate, the crystal used, whether there is signal lock and when the input buffer is full.
If you intend to build the Pi into your solution containing a DAC board, you can run the I2S outputs from the Kali directly provided they are only a few cm in length. I2S was never designed to run from one chassis to another, so here you will need another board in order to convert the delicate I2S signal into something more robust for sending along, say, a 1m cable. The two most common methods of transport are I2S over HDMI and I2S over ethernet. You will need to select a system depending on the needs of your DAC. In either case, wiring the Kali to the 'send' board should be trivial provided you take care to keep the wire runs very short.
Here is an example I2S send board for HDMI output to a standard HDMI cable. This will work with DACs from PS Audio, Audio-GD, Gustard, LKS and many others.
As some of you know, the Pi makes for an excellent audio streamer, having sufficient performance, low power requirements and small size to suit the job well. There are also several software builds to make a streamer from a Pi such that you can pick your flavour to suit. Furthermore, if you use a plug-in DAC then you have a nice all-in-one solution.
However, many people want to use an external DAC for even higher performance and that tends to fall into three camps: USB, S/PDIF and I2S. If you want the best S/PDIF feed available, there are only two choices: the Allo DigiOne or DigiOne Signature. The equivalent for I2S (although not a complete solution in itself) is the Allo Kali.
What the Kali does is to ignore the inaccurate timing of the signal derived by the Pi itself and generate a highly accurate one. The Pi has only a single crystal clock whereas the Kali has two: one for 44.1kHz and its derivatives (such as 88.2kHz) and the other for 48kHz and its derivatives (such as 96kHz). These plus the very low jitter and dedicate power supply routing dish out signals with only 4ps of jitter, ideal for a high end DAC.
The board itself has a handful of LEDs to help diagnose your setup which I have found very useful. They tell you the incoming sample rate, the crystal used, whether there is signal lock and when the input buffer is full.
If you intend to build the Pi into your solution containing a DAC board, you can run the I2S outputs from the Kali directly provided they are only a few cm in length. I2S was never designed to run from one chassis to another, so here you will need another board in order to convert the delicate I2S signal into something more robust for sending along, say, a 1m cable. The two most common methods of transport are I2S over HDMI and I2S over ethernet. You will need to select a system depending on the needs of your DAC. In either case, wiring the Kali to the 'send' board should be trivial provided you take care to keep the wire runs very short.
Here is an example I2S send board for HDMI output to a standard HDMI cable. This will work with DACs from PS Audio, Audio-GD, Gustard, LKS and many others.