SDI to Audio 4K: analog and AES groups for a console or CLARITY M

Four outputs do not mean four SDI inputs

Count the independent SDI signals and the channels you need to extract from each one. Draw a path for each source and note whether the destination needs analog audio or AES/EBU. Then determine how many converters and cables you need.

The July 2024 Blackmagic Converters manual, page 59 identifies four output jacks. In analog mode, each provides one channel. In AES/EBU mode, each carries a pair. Record what should reach each receiver input before counting adapters.

SDI IN is the main source and ALT SDI IN is the redundant input: they do not provide two independent audio extractions. Four recorders with different signals need a map showing four signal paths. Keep that distinction when deciding how many converters to use; cascading units to extract more channels from the same signal does not add inputs for other sources.

Switch 8 selects the mode; switches 6 and 5 select the group

On page 60, switch 8 set to OFF selects balanced analog audio; ON selects digital AES/EBU. For analog channels 1–4, the example sets switches 8, 6 and 5 to OFF. Read the group table for the selected mode: the same 6/5 combination does not select the same number of channels in both modes.

The manufacturer's AES table documents 1–8 and 9–16 with switch 6 set to OFF. These are the two documented combinations; do not assume additional combinations with switch 6 set to ON. If a voice is missing or a different mix appears, check the channels carried by the source first, then the selected group.

Test with a channel identification signal, followed by actual event content. Record what each jack delivers and what the destination receives. The SDI to HDMI 6G guide uses a different pair-selection scheme; its switches 4/3/2 are not the SDI to Audio 4K procedure.

SDI OUT carries the same signal to another audio extraction stage

The manufacturer describes SDI OUT as a loop-through output and explains how to cascade another SDI to Audio 4K to extract additional channels from the same input, page 59. Draw the order of the units, each unit's group and the final video receiver. Identify the mode at every stage.

Start by checking one extraction stage and the signal received at the SDI destination. Then add the next stage and repeat channel identification and the picture/audio check at the end of the path. Save results for each connector; checking the first box does not verify the final destination.

The page 61 instructions describe Output Levels in the Audio tab of Converters Setup: per-channel gain, pair linking with link, and reset to 0 dB. Save the existing values before changing gain. Adjust levels after confirming the mode and group; gain cannot recover content that is absent from those channels.

AES to CLARITY M: check the adapter and the complete signal path

To send AES from the converter's TRS jacks to the meter's BNC inputs, check each adapter's function and the complete cable path. Connector shape does not establish the required electrical conversion.

The CLARITY M manual, version 2.0, May 10, 2018, pages 4–5 and 9 documents six unbalanced 75 Ω AES3 channels on three BNC connectors on the SUB-D cable. For AES/EBU connections in surround use, it recommends three Neutrik NA2FBNC adapters.

Neutrik's NA2FBNC product information describes the female XLR/BNC adapter and its wiring. The NADITBNC-FX information documents conversion from a balanced 110 Ω line to 75 Ω coaxial. These are different technical descriptions. A transformer can be passive: the word passive alone does not establish whether an adapter performs that conversion.

Record the exact adapter model, the cables in each segment, the connectors and the channel mapping. A six-channel test has three AES paths to check separately. Compare the 4K's balanced output with the meter's input requirements before connecting, then test the complete setup.

CLARITY M: AES source, digital lock and channel order

In the version 2.0 manual, pages 11 and 15, System (SYS) lets you select AES 1, 2, 3 or 1–3 (5.1 surround). Save measurements before changing the source: the manual warns that this resets the meters. Version 2.0 refers to the document; also record the version installed on the unit.

Source Section shows red for No Digital Lock and green for Digital Lock. Use that indication to check digital reception, then send a channel identification signal. Lock alone does not tell you whether a voice is on the expected channel.

For surround, the Film/ITU channel-order parameter changes only how channels are displayed. The manual specifies fixed ITU audio routing: L-R-C-LFE-LS-RS. If Center and LFE appear swapped, changing the display order does not reroute the signal. Compare the source map with the three received pairs.

The page 19 specifications limit surround in standalone mode to 44.1 or 48 kHz and list separate supported rates for plug-in mode. Record the source sample rate and actual mode before testing. The page also includes the DB15 cable pinout; check the cable in use against that documentation rather than assuming another SUB-D cable has the same assignment.

Use the groups and reception worksheet to complete the test

Complete the blank SDI to Audio 4K and CLARITY M worksheet. It covers sources, groups, jacks, mode, AES adaptation, sample rate, SDI receiver and results by channel. If you are only extracting audio to a console, complete that branch and mark the meter as not used.

Test channel identification first, then actual content. Repeat the planned group changes, the cascaded SDI path and the meter reception test. Keep a record of the initial setup and the configuration agreed for the event, including open items and who is responsible for them.

For event planning, add this map to the recording or hybrid panel plan. GLMedia can review video processing and distribution together with audio systems, based on the specified models and destinations.

ALT SDI IN: test switchover and return with audio

Apply this procedure to the Mini Converter SDI to Audio 4K. Check the unit's label before using the table: Audio to SDI performs a different function and does not necessarily share these controls.

For the SDI to Audio 4K, page 59 of the July 2024 manual documents SDI IN as the main input and ALT SDI IN as the backup. With both connected, ALT takes over if the SDI IN signal fails; SDI LOCK flashes to indicate the change. The diagram on page 61 shows Redundant Input Automatic Change Over before audio extraction.

Prepare A and B with distinct picture and audio identification. Check each source separately at the destinations you will use, keeping the extraction mode and group unchanged. Compare the video format and channel assignments: a backup carrying the voice in another group may produce a picture without the expected audio.

Test off-air with both signals present. Interrupt the agreed section of the main path and observe the LED, SDI OUT and every audio output in use. Then restore A and record which source reaches each destination, how long it takes to stabilize and any audible or visible interruption. The cited section does not specify switching time, seamless transitions or the policy for returning to the main input.

A black picture, frozen frame or missing voice does not by itself identify a loss of SDI signal. If the source is still outputting a signal, do not assume ALT will detect that content fault. Record the symptom and test that scenario separately; you also need a switching procedure agreed with the operators.

Multiple SDI feeds: check priority and each stage's output

If you want automatic priority selection between several sources, check what each stage outputs when it loses its input. An intermediate output that continues sending SDI may prevent the next stage from detecting a loss, even if the content is no longer correct.

The 4K manual calls SDI OUT a loop-through output and describes cascading units to extract more channels from the same source, pages 59 and 61. That documented use does not validate a cascade as a selector for several independent feeds; check the priority logic and content at each stage.

If you are evaluating cascaded redundant inputs, draw every stage's connectors and the intended priority order. Test one source alone, no source and two sources present. Observe both the intermediate output and the final destination: a stage that outputs a signal can change what the next stage detects. If the result does not follow the required priority, revise the design before using it at the event.

Also identify dependencies shared by A and B: the final converter, power and the connection to the receiver. Input redundancy does not establish backup coverage for the whole chain. Record which failure the setup covers and which requires another path.

Use the blank ALT and backup worksheet to record switchover, return, simultaneous sources and audio at each destination. Add it to the conference continuity plan and the recording map. GLMedia can review the video processing and distribution path once the models and outstanding tests are identified.