How to Route CobraNet Between I-Tech HD Amplifiers

Table of Contents

Brand: Models: Overview: CobraNet Basics: Example files: Advanced Settings and Foldback 4x3500HD amplifiers I-Tech HD 2 channel amplifiers CTs Series+PIP-USP4/CN amplifiers Source Settings: 4x3500HD amplifiers I-Tech HD 2 channel amplifiers CTs Series+PIP-USP4/CN amplifiers

Brand:

Crown

Models:

4x3500HDS, 4x3500HDB
IT12000HD, IT9000HD, IT5000HD
CTS600USP4CN, CTS1200USP4CN, CTS2000USP4CN, CTS3000USP4CN

Overview:

I-Tech HD amplifiers, and also the older CTS amplifiers with PIP-USP4/CN cards, may be setup similarly as an audio source to CobraNet using the Foldback settings in the CobraNet Advanced Settings or Output Configuration.
These amplifiers use the CM-2 CobraNet card and have similar CobraNet features.

CobraNet technology and support from its primary developer, Cirrus Logic, have reached their end-of-life phase. It is not recommended for use in new audio system designs.
However, CobraNet is still used in legacy systems. As of 2026 HARMAN Pro still produces and supports the CobraNet-compatible I-Tech HD amplifiers.

CobraNet Basics:

CobraNet does not use TCP/IP protocol. It operates exclusively at Layer 2 (Data Link Layer) and cannot cross routers.
For best results use quality managed switches operating at 100 Mbps or higher (Fast Ethernet or Gigabit).
To route CobraNet audio, you must keep all devices on the same Layer 2 local network (VLAN) and configure channel routing using bundle numbers.
Each CobraNet device can typically transmit and receive up to 4 bundles simultaneously, with each bundle carrying up to 8 audio channels.
Multicast Bundles: Numbers 1 - 255. These broadcast to the entire network.
- Proper configuration of IGMP Snooping is essential for multicast to work correctly. Exact details will depend on the capabilities of your network switches.
Unicast Bundles: Numbers 256 - 65,279. These send audio directly from one specific source device to another specific destination device.

Bundle Limitations: A basic Ethernet network supports up to 64 audio channels (8 fully loaded bundles) on a basic 100Base-TX connection. Full duplex switched networks will allow more bandwidth. Nonetheless, it is best rely on unicast bundles for point-to-point communication to save bandwidth, reserving multicast bundles for one-to-many routing.
- 4x3500HD may be setup to transmit up to 4 bundles.
- The 2 channel amplifiers can transmit only 1 bundle.
The Processing Sample Rate of the amplifier sets its CobraNet sample rate. Options are 96kHz (amplifier default) or 48kHz. Source and Destination sample rates must match for audio to be produced.
- At 96kHz bundles may be configured with up to 4 channels each.
- At 48kHz bundles may be configured with up to 8 channels each.

Latency Settings: CobraNet provides real-time audio and requires predictable forwarding delays. The amplifiers' CobraNet latency setting (5.33 ms, 2.66 ms, or 1.33 ms) dictates the maximum number of network switch hops permitted. The default 5.33 ms latency allows for a maximum of 7 switch hops.

The Conductor is the automatically-elected device responsible for supplying the master clock timing and coordinating audio packet transmission across the entire system.
- Without an active Conductor, digital audio cannot pass through a CobraNet network.
- Devices must be assigned a Conductor Priority from 0 - 255. For example, 0 meaning never conductor, 32 as a normal default, 255 as the highest priority. If the active Conductor loses power or drops offline, the remaining devices immediately re-arbitrate to elect a new Conductor from the active pool.

Example files:

The screenshots used in this tech support guide were taken from the example files in the ZIP downloadable below.
They were created as a quick example of how to route audio from one amplifier to another using CobraNet.
Source audio used was the Signal Generator on the source amplifier.
This was sent to an amplifier output, which was then routed to a CobraNet bundle via Foldback.

Audio Architect v2.55.3 was used to create these examples.

CobraNet Foldback Tests.zip

Advanced Settings and Foldback

The CobraNet: Advanced Settings panel is where you will setup the I-Tech HD source audio to output onto CobraNet, aka Foldback. This is also where the CobraNet Priority and Latency settings are made.
On the CTS amplfiers, the CobraNet foldback is set on the Output Configuration panel.

4x3500HD amplifiers

Open the amplifier's device panel by double-clicking the amplifier in its rack.
Double-click any Input button to open the Source Routing panel for that input.
Press the Source Configuration button in the upper left to open the Source Configuration panel.

Then:

Select the CobraNet Inputs tab in the upper right to access the CobraNet input settings.
Press the Advanced Settings button in the lower right to open the CobraNet: Advanced Settings panel.

In the CobraNet Foldback section on the right, up to 4 bundles may be setup for output: TxA, TxB, TxC, TxD.

By default TxA is selected, set to bundle 0 (disabled).
Set a bundle number 1 to 255 for multicast output, 256 to 65,279 for unicast.
Setup the 8 possible source choices from None, Analog inputs 1-4, AES inputs 1-4, or Amp output voltage 1-4.
Then choose one of these Output Sources, or None, for each of the bundle Slots.

Be sure to set the Conductor Priority of at least one CobraNet device to a non-0 number.
Confirm the latency of all the devices is the same.

I-Tech HD 2 channel amplifiers

The CobraNet: Advanced Settings panel is where you will setup the CobraNet source audio, aka Foldback.

Open the amplifier's device panel by double-clicking the amplifier in its rack.
Double-click any Input button to open the Source Routing panel for that input.
Press the Source Configuration button in the upper left to open the Source Configuration panel.

Then:

Press the Advanced Settings button in the lower right to open the CobraNet: Advanced Settings panel.

In the Foldback section on the right, one bundle may be setup for output.
By default the bundle is set to 0 (disabled).

Set a bundle number of 1 to 255 for multicast output, 256 to 65,279 for unicast.
Choose from None, Analog inputs 1-4, AES inputs 1-4, or Amp output voltage 1-4 for each of the bundle Slots.
Be sure to set the Conductor Priority of at least one CobraNet device to a non-0 number.
Confirm the latency of all the devices is the same.

CTs Series+PIP-USP4/CN amplifiers

The Output Configuration panel is where you will setup the CobraNet source audio, aka Foldback.

Open the amplifier's device panel by double-clicking the amplifier in its rack.
Double-click any Input button to open the Source Routing panel for that input.

Then:

Press the Output Configuration button in the upper left to open the Output Configuration panel.

In the Foldback section on the right, one bundle may be setup for output.
By default the bundle is set to 0 (disabled).

Set a bundle number 1 to 255 for multicast output, 256 to 65,279 for unicast.
Choose from None, Analog inputs 1-4, AES inputs 1-4, or Amp output voltage 1-4 for each of the bundle Slots.

The CobraNet: Advanced Settings panel is where you will setup the CobraNet Conductor Priority and Latency.

Open the amplifier's device panel by double-clicking the amplifier in its rack.
Double-click any Input button to open the Source Routing panel for that input.

Then:

Press the Source Configuration button in the upper left to open the Source Configuration panel.
Press the Advanced Settings button in the lower right to open the CobraNet: Advanced Settings panel.

Be sure to set the Conductor Priority of at least one CobraNet device to a non-0 number.
Confirm the latency of all the devices is the same.