Sample Rates Overview

The M-1620 Pro supports the following sample rates:

Supported sample rates
Single speed	44.1 kHz, 48 kHz
Double speed	88.2 kHz, 96 kHz
Quad speed	176.4 kHz, 192 kHz

If the device is clock reference ("leader"/"master"), these rates always correspond to the actual sample rate used.

Following an External Clock Reference

When the device is synchronized to an external clock reference ("follower"/"slave"), certain deviations are automatically accepted to avoid interruption of the outgoing audio signal when the sample rate changes. This is called Intelligent Clock Control (ICC). It also handles deriving a sample rate of double or quad speed based on an incoming rate.

Intelligent Clock Control (ICC)
Input	Clock at input	Selected Sample Rate	Resulting Sample Rate
MADI	44.1	44.1	44.1
MADI	44.1	48	44.1 with warning
MADI	44.1	88.2	88.2
MADI	44.1	96	88.2 with warning
MADI	44.1	176.4	176.4
MADI	44.1	192	176.4 with warning
MADI	48	44.1	48 with warning
MADI	48	48	48
MADI	48	88.2	96 with warning
MADI	48	96	96
MADI	48	176.4	192 with warning
MADI	48	192	192
MADI 96k	88.2	44.1	warning (no sync)
MADI 96k	88.2	48	warning (no sync)
MADI 96k	88.2	88.2	88.2
MADI 96k	88.2	96	88.2 with warning
MADI 96k	88.2	176.4	warning (no sync)
MADI 96k	88.2	192	warning (no sync)
MADI 96k	96	44.1	warning (no sync)
MADI 96k	96	48	warning (no sync)
MADI 96k	96	88.2	96 with warning
MADI 96k	96	96	96
MADI 96k	96	176.4	warning (no sync)
MADI 96k	96	192	warning (no sync)
Word Clock	44.1	44.1	44.1
Word Clock	44.1	48	44.1 (with warning)
Word Clock	44.1, 88.2	88.2	88.2
Word Clock	44.1, 88.2	96	88.2 with warning
Word Clock	44.1, 88.2, 176.4	176.4	176.4
Word Clock	44.1, 88.2, 176.4	192	176.4 with warning
Word Clock	48	44.1	48 with warning
Word Clock	48	48	48
Word Clock	48, 96	88.2	96 with warning
Word Clock	48, 96	96	96
Word Clock	48, 96, 192	176.4	192 with warning
Word Clock	48, 96, 192	192	192

There is no ICC mechanism necessary for AVB; the device will always use the exact clock from the corresponding AVB stream.

It is not recommended to synchronize devices with a higher sample rate than the current sample rate, because two devices could choose different edges of the incoming clock signal.

ICC does not affect outgoing AVB streams. Outgoing AVB streams will always correspond to the sample rate set in the CLOCK section. If the reference clock changes its frequency, outgoing AVB streams will be interrupted.

Number of Channels

The supported number of channels per port or stream at different sample rates is shown in the following table.

Supported number of audio channels per stream/port and direction at different sample rates
	44.1 kHz	48 kHz	88.2 kHz	96 kHz	176.4 kHz	192 kHz
MADI 56 Ch	56	56	28	28	14	14
MADI 64 Ch	64	64	32	32	16	16
MADI 56 Ch + 96k	---	---	28	28	---	---
MADI 64 Ch + 96k	---	---	32	32	---	---
AVB 1-8 Ch stream	1-8	1-8	1-8	1-8	1-8	1-8
AVB 12 Ch stream	12	12	12	12	---	---
AVB 16 Ch stream	16	16	---	---	---	---

Since there are two independent MADI ports, the total supported number of channels can be multiplied by two. Since there are eight independent AVB streams, the total supported number of channels can be multiplied by eight. The analog channel count remains identical at all sample rates.

Selecting a Sample Rate

To configure the device sample rate on the device:

Enter the CLOCK section.
Rotate the encoder to highlight the current sample rate.
Push the encoder. Two blue arrows will appear to indicate that the encoder can now be used to change the current setting.
Rotate the encoder until the preferred sample rate is shown.
Push the encoder again to activate the setting.

To configure the device sample rate on the web remote:

Locate the Select sample rate drop down menu in the CLOCK section.
Select a sample rate from the drop down menu. The new rate is applied immediately.

Effects of Sample Rate Changes on Existing Routing

The M-1620 Pro saves one routing table per preset, regardless of sample rate. A change of sample rate or MADI frame mode can reduce the number of input and output channels available for routing. This does not alter the routing table. Any existing routing is hidden until another change of sample rate re-enables the channels.

Example:

A routing is created at 96 kHz with 32 channels, sending the MADI coaxial Input 1-32 to optical MADI Output 1-32. If the sample rate is now changed to 176.4 kHz and the 56 Ch frame is activated, only the first 14 channels of MADI coaxial input are routed to the optical output. Switching the sample rate to 44.1 or 48 kHz will reveal the previous routing for 32 channels.