8-Channel AES3 Distribution Amplifier, a ESP32 project

This 8-channel AES3 distribution amplifier takes a single AES3 digital audio input and distributes it to two independent outputs, each carrying all eight channels. Built around isolation transformers and shielded connectors, the amplifier maintains signal integrity across professional audio installations while rejecting common-mode interference.

The guide provides a complete parts list, wiring diagram, and step-by-step assembly instructions for building the amplifier in a metal enclosure. The AES3 signal path is entirely passive and transformer-based, requiring only a 5 V DC power input for the ESP32 controller. Assembly proceeds from preparing the enclosure through fitting input and output stages, with a final inspection and single-link test before full deployment.

Wiring diagram

Gather all the parts

Qty	Component
1	Shielded RJ45 input connector Shielded panel RJ45 A metal-shielded eight-pin panel connector that receives all four balanced AES3 links.
1	Shielded RJ45 output connector A Shielded panel RJ45 A metal-shielded eight-pin panel connector carrying the first isolated copy of all four AES3 links.
1	Shielded RJ45 output connector B Shielded panel RJ45 A metal-shielded eight-pin panel connector carrying the second isolated copy of all four AES3 links.
1	Locking 5 V DC panel input Locking 5 V DC connector A panel connector that accepts power from the certified external 5 volt supply.
1	110 ohm AES3 1:1 input isolation transformer 1:1, 110 Ω AES3 rated An isolation transformer for AES3 link 1, carrying audio channels 1 and 2.
1	110 ohm AES3 1:1 input isolation transformer 1:1, 110 Ω AES3 rated An isolation transformer for AES3 link 2, carrying audio channels 3 and 4.
1	110 ohm AES3 1:1 input isolation transformer 1:1, 110 Ω AES3 rated An isolation transformer for AES3 link 3, carrying audio channels 5 and 6.
1	110 ohm AES3 1:1 input isolation transformer 1:1, 110 Ω AES3 rated An isolation transformer for AES3 link 4, carrying audio channels 7 and 8.
1	110 ohm AES3 1:1 output isolation transformer — Output A channels 1–2 1:1, 110 Ω AES3 rated An AES3-rated transformer that isolates the first balanced output link on Output A.
1	110 ohm AES3 1:1 output isolation transformer — Output A channels 3–4 1:1, 110 Ω AES3 rated An AES3-rated transformer that isolates the second balanced output link on Output A.
1	110 ohm AES3 1:1 output isolation transformer — Output A channels 5–6 1:1, 110 Ω AES3 rated An AES3-rated transformer that isolates the third balanced output link on Output A.
1	110 ohm AES3 1:1 output isolation transformer — Output A channels 7–8 1:1, 110 Ω AES3 rated An AES3-rated transformer that isolates the fourth balanced output link on Output A.
1	110 ohm AES3 1:1 output isolation transformer — Output B channels 1–2 1:1, 110 Ω AES3 rated An AES3-rated transformer that isolates the first balanced output link on Output B.
1	110 ohm AES3 1:1 output isolation transformer — Output B channels 3–4 1:1, 110 Ω AES3 rated An AES3-rated transformer that isolates the second balanced output link on Output B.
1	110 ohm AES3 1:1 output isolation transformer — Output B channels 5–6 1:1, 110 Ω AES3 rated An AES3-rated transformer that isolates the third balanced output link on Output B.
1	110 ohm AES3 1:1 output isolation transformer — Output B channels 7–8 1:1, 110 Ω AES3 rated An AES3-rated transformer that isolates the fourth balanced output link on Output B.
1	THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 1 50 Mb/s, 5 V A high-speed 5 volt differential interface chip used only to receive the channels 1–2 AES3 link.
1	THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 2 50 Mb/s, 5 V A high-speed 5 volt differential interface chip used only to receive the channels 3–4 AES3 link.
1	THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 3 50 Mb/s, 5 V A high-speed 5 volt differential interface chip used only to receive the channels 5–6 AES3 link.
1	THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 4 50 Mb/s, 5 V A high-speed 5 volt differential interface chip used only to receive the channels 7–8 AES3 link.
1	THVD1452 high-speed RS-422 driver — Output A link 1 high-speed 5 V RS-422 A 5 volt high-speed differential driver that sends the channels 1–2 AES3 link to Output A.
1	THVD1452 high-speed RS-422 driver — Output A link 2 high-speed 5 V RS-422 A 5 volt high-speed differential driver that sends the channels 3–4 AES3 link to Output A.
1	THVD1452 high-speed RS-422 driver — Output A link 3 high-speed 5 V RS-422 A 5 volt high-speed differential driver that sends the channels 5–6 AES3 link to Output A.
1	THVD1452 high-speed RS-422 driver — Output A link 4 high-speed 5 V RS-422 A 5 volt high-speed differential driver that sends the channels 7–8 AES3 link to Output A.
1	THVD1452 high-speed RS-422 driver — Output B link 1 high-speed 5 V RS-422 A 5 volt high-speed differential driver that sends the channels 1–2 AES3 link to Output B.
1	THVD1452 high-speed RS-422 driver — Output B link 2 high-speed 5 V RS-422 A 5 volt high-speed differential driver that sends the channels 3–4 AES3 link to Output B.
1	THVD1452 high-speed RS-422 driver — Output B link 3 high-speed 5 V RS-422 A 5 volt high-speed differential driver that sends the channels 5–6 AES3 link to Output B.
1	THVD1452 high-speed RS-422 driver — Output B link 4 high-speed 5 V RS-422 A 5 volt high-speed differential driver that sends the channels 7–8 AES3 link to Output B.
1	74AHCT244 octal buffer — four AES3 link fan-out SOIC-20, 5 V A fast 5 volt logic buffer that makes two separate copies of each of the four recovered AES3 signals.
1	Resistor 110 Ω, 1%, 0603 Through-hole resistor (current-limiting in series with an LED)
1	Resistor 110 Ω, 1%, 0603 Through-hole resistor (current-limiting in series with an LED)
1	Resistor 110 Ω, 1%, 0603 Through-hole resistor (current-limiting in series with an LED)
1	Resistor 110 Ω, 1%, 0603 Through-hole resistor (current-limiting in series with an LED)

Assemble it in 7 steps

1. Prepare the metal enclosure

Use a metal rack enclosure with three shielded RJ45 panel cut-outs marked INPUT, OUTPUT A, and OUTPUT B, plus one locking 5 V DC input cut-out. Bond each RJ45 metal shell directly to the enclosure with a short, wide connection; this gives cable noise a safe path to the chassis.

Mark every RJ45 port “AES3 ONLY — NOT ETHERNET — NO PoE” before fitting it.
Do not connect these ports to an Ethernet switch or PoE injector; that can damage the distribution amplifier and connected audio equipment.

2. Fit the input side parts

Fit the four input transformers beside the INPUT connector. Keep each transformer close to its matching RJ45 pair: pins 1–2 for link 1, pins 3–6 for link 2, pins 4–5 for link 3, and pins 7–8 for link 4. Fit each 110 Ω 1% resistor directly across that transformer’s receiver-side pair.

Keep the two copper tracks of each pair the same length and route them next to one another.
Do not substitute Ethernet magnetics for the AES3 transformers; the wrong transformer can distort the digital-audio signal.

3. Fit the receiver and copying stage

Fit the four receiver ICs and the 74AHCT244 copying buffer near the input transformers. Add a 100 nF ceramic capacitor from 5 V to ground at every IC supply pin pair, placed as close to the chip as possible.

The buffer makes one separate electrical copy for Output A and another for Output B; it does not decode or alter the audio.
Keep the input transformer secondary tracks short; long tracks can pick up noise and cause dropouts.

4. Fit the Output A path

Fit Output A’s four driver ICs and four output transformers between the copying buffer and the OUTPUT A connector. Route the transformer secondaries to pins 1–2, 3–6, 4–5, and 7–8 in that order.

Keep every outgoing pair as a 110 Ω differential pair and avoid branches or unused trace stubs.
Swapping the plus and minus wires of one pair reverses that AES3 link and may prevent the receiving equipment from locking.

5. Fit the Output B path

Fit Output B’s four driver ICs and four output transformers in the same way. Route the output transformer secondaries to pins 1–2, 3–6, 4–5, and 7–8 on OUTPUT B.

Output A and Output B must remain separate after the copying buffer so a fault or unplugged cable on one output does not load the other.
Never join an Output A pair directly to the same Output B pair; the two outputs must be separately driven and transformer-isolated.

6. Wire and protect the 5 V input

Bring the certified regulated 5 V supply into the locking DC connector, then route it through reverse-polarity and over-current protection before the 5 V plane. Connect its return to the circuit ground plane; do not use the RJ45 signal pairs as power or ground wires.

Use a supply rated for at least 1 A even though the circuit draws less; it will run cooler and has margin.
Check the connector polarity with a meter before plugging in the board—reversed 5 V power can damage every interface chip.

7. Inspect and test one link first

Before connecting studio equipment, check for shorts between 5 V and ground. Then connect a known AES3 source to INPUT and a known AES3 receiver to Output A using the correct shielded 110 Ω cable. Verify channels 1–2 first, then repeat for the other three pairs and Output B.

If one pair fails, first check the pin pair order: 1–2, 3–6, 4–5, then 7–8.
Power down before changing soldered connections; accidental shorts can damage the drivers or connected audio hardware.

Review all connections

1. Connections between "dc_input" and "ESP32"

Function	dc_input	ESP32
`power`	+5V	5V
`ground`	GND	GND

2. Connections between "rj45_in" and "ESP32"

Function	rj45_in	ESP32
`data`	1 → 110 ohm AES3 1:1 input isolation transformer PRI+	EXT
`data`	2 → 110 ohm AES3 1:1 input isolation transformer PRI-	EXT
`data`	3 → 110 ohm AES3 1:1 input isolation transformer PRI+	EXT
`data`	6 → 110 ohm AES3 1:1 input isolation transformer PRI-	EXT
`data`	4 → 110 ohm AES3 1:1 input isolation transformer PRI+	EXT
`data`	5 → 110 ohm AES3 1:1 input isolation transformer PRI-	EXT
`data`	7 → 110 ohm AES3 1:1 input isolation transformer PRI+	EXT
`data`	8 → 110 ohm AES3 1:1 input isolation transformer PRI-	EXT
`ground`	SHELL → earthed metal enclosure	EXT

3. Connections between "rj45_out_a" and "ESP32"

Function	rj45_out_a	ESP32
`ground`	SHELL → earthed metal enclosure	EXT

4. Connections between "rj45_out_b" and "ESP32"

Function	rj45_out_b	ESP32
`ground`	SHELL → earthed metal enclosure	EXT

5. Connections between "in_tx1" and "ESP32"

Function	in_tx1	ESP32
`data`	SEC+ → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 1 IN+	EXT
`data`	SEC- → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 1 IN-	EXT

6. Connections between "term1" and "ESP32"

Function	term1	ESP32
`digital`	P1 → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 1 IN+	EXT
`digital`	P2 → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 1 IN-	EXT

7. Connections between "in_tx2" and "ESP32"

Function	in_tx2	ESP32
`data`	SEC+ → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 2 IN+	EXT
`data`	SEC- → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 2 IN-	EXT

8. Connections between "term2" and "ESP32"

Function	term2	ESP32
`digital`	P1 → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 2 IN+	EXT
`digital`	P2 → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 2 IN-	EXT

9. Connections between "in_tx3" and "ESP32"

Function	in_tx3	ESP32
`data`	SEC+ → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 3 IN+	EXT
`data`	SEC- → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 3 IN-	EXT

10. Connections between "term3" and "ESP32"

Function	term3	ESP32
`digital`	P1 → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 3 IN+	EXT
`digital`	P2 → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 3 IN-	EXT

11. Connections between "in_tx4" and "ESP32"

Function	in_tx4	ESP32
`data`	SEC+ → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 4 IN+	EXT
`data`	SEC- → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 4 IN-	EXT

12. Connections between "term4" and "ESP32"

Function	term4	ESP32
`digital`	P1 → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 4 IN+	EXT
`digital`	P2 → THVD1452 50 Mb/s full-duplex RS-422 transceiver — receiver 4 IN-	EXT

13. Connections between "rx_link1" and "ESP32"

Function	rx_link1	ESP32
`digital`	OUT → 74AHCT244 octal buffer — four AES3 link fan-out IN1	EXT
`power`	VCC	5V
`ground`	GND	GND

14. Connections between "rx_link2" and "ESP32"

Function	rx_link2	ESP32
`digital`	OUT → 74AHCT244 octal buffer — four AES3 link fan-out IN2	EXT
`power`	VCC	5V
`ground`	GND	GND

15. Connections between "rx_link3" and "ESP32"

Function	rx_link3	ESP32
`digital`	OUT → 74AHCT244 octal buffer — four AES3 link fan-out IN3	EXT
`power`	VCC	5V
`ground`	GND	GND

16. Connections between "rx_link4" and "ESP32"

Function	rx_link4	ESP32
`digital`	OUT → 74AHCT244 octal buffer — four AES3 link fan-out IN4	EXT
`power`	VCC	5V
`ground`	GND	GND

17. Connections between "drv_a1" and "ESP32"

Function	drv_a1	ESP32
`data`	OUT+ → 110 ohm AES3 1:1 output isolation transformer — Output A channels 1–2 PRI+	EXT
`data`	OUT- → 110 ohm AES3 1:1 output isolation transformer — Output A channels 1–2 PRI-	EXT
`power`	VCC	5V
`ground`	GND	GND

18. Connections between "drv_a2" and "ESP32"

Function	drv_a2	ESP32
`data`	OUT+ → 110 ohm AES3 1:1 output isolation transformer — Output A channels 3–4 PRI+	EXT
`data`	OUT- → 110 ohm AES3 1:1 output isolation transformer — Output A channels 3–4 PRI-	EXT
`power`	VCC	5V
`ground`	GND	GND

19. Connections between "drv_a3" and "ESP32"

Function	drv_a3	ESP32
`data`	OUT+ → 110 ohm AES3 1:1 output isolation transformer — Output A channels 5–6 PRI+	EXT
`data`	OUT- → 110 ohm AES3 1:1 output isolation transformer — Output A channels 5–6 PRI-	EXT
`power`	VCC	5V
`ground`	GND	GND

20. Connections between "drv_a4" and "ESP32"

Function	drv_a4	ESP32
`data`	OUT+ → 110 ohm AES3 1:1 output isolation transformer — Output A channels 7–8 PRI+	EXT
`data`	OUT- → 110 ohm AES3 1:1 output isolation transformer — Output A channels 7–8 PRI-	EXT
`power`	VCC	5V
`ground`	GND	GND

21. Connections between "drv_b1" and "ESP32"

Function	drv_b1	ESP32
`data`	OUT+ → 110 ohm AES3 1:1 output isolation transformer — Output B channels 1–2 PRI+	EXT
`data`	OUT- → 110 ohm AES3 1:1 output isolation transformer — Output B channels 1–2 PRI-	EXT
`power`	VCC	5V
`ground`	GND	GND

22. Connections between "drv_b2" and "ESP32"

Function	drv_b2	ESP32
`data`	OUT+ → 110 ohm AES3 1:1 output isolation transformer — Output B channels 3–4 PRI+	EXT
`data`	OUT- → 110 ohm AES3 1:1 output isolation transformer — Output B channels 3–4 PRI-	EXT
`power`	VCC	5V
`ground`	GND	GND

23. Connections between "drv_b3" and "ESP32"

Function	drv_b3	ESP32
`data`	OUT+ → 110 ohm AES3 1:1 output isolation transformer — Output B channels 5–6 PRI+	EXT
`data`	OUT- → 110 ohm AES3 1:1 output isolation transformer — Output B channels 5–6 PRI-	EXT
`power`	VCC	5V
`ground`	GND	GND

24. Connections between "drv_b4" and "ESP32"

Function	drv_b4	ESP32
`data`	OUT+ → 110 ohm AES3 1:1 output isolation transformer — Output B channels 7–8 PRI+	EXT
`data`	OUT- → 110 ohm AES3 1:1 output isolation transformer — Output B channels 7–8 PRI-	EXT
`power`	VCC	5V
`ground`	GND	GND

25. Connections between "out_tx_a1" and "ESP32"

Function	out_tx_a1	ESP32
`data`	SEC+ → Shielded RJ45 output connector A 1	EXT
`data`	SEC- → Shielded RJ45 output connector A 2	EXT

26. Connections between "out_tx_a2" and "ESP32"

Function	out_tx_a2	ESP32
`data`	SEC+ → Shielded RJ45 output connector A 3	EXT
`data`	SEC- → Shielded RJ45 output connector A 6	EXT

27. Connections between "out_tx_a3" and "ESP32"

Function	out_tx_a3	ESP32
`data`	SEC+ → Shielded RJ45 output connector A 4	EXT
`data`	SEC- → Shielded RJ45 output connector A 5	EXT

28. Connections between "out_tx_a4" and "ESP32"

Function	out_tx_a4	ESP32
`data`	SEC+ → Shielded RJ45 output connector A 7	EXT
`data`	SEC- → Shielded RJ45 output connector A 8	EXT

29. Connections between "out_tx_b1" and "ESP32"

Function	out_tx_b1	ESP32
`data`	SEC+ → Shielded RJ45 output connector B 1	EXT
`data`	SEC- → Shielded RJ45 output connector B 2	EXT

30. Connections between "out_tx_b2" and "ESP32"

Function	out_tx_b2	ESP32
`data`	SEC+ → Shielded RJ45 output connector B 3	EXT
`data`	SEC- → Shielded RJ45 output connector B 6	EXT

31. Connections between "out_tx_b3" and "ESP32"

Function	out_tx_b3	ESP32
`data`	SEC+ → Shielded RJ45 output connector B 4	EXT
`data`	SEC- → Shielded RJ45 output connector B 5	EXT

32. Connections between "out_tx_b4" and "ESP32"

Function	out_tx_b4	ESP32
`data`	SEC+ → Shielded RJ45 output connector B 7	EXT
`data`	SEC- → Shielded RJ45 output connector B 8	EXT

33. Connections between "logic_fanout" and "ESP32"

Function	logic_fanout	ESP32
`power`	VCC	5V
`ground`	GND	GND
`digital`	A1 → THVD1452 high-speed RS-422 driver — Output A link 1 IN	EXT
`digital`	A2 → THVD1452 high-speed RS-422 driver — Output A link 2 IN	EXT
`digital`	A3 → THVD1452 high-speed RS-422 driver — Output A link 3 IN	EXT
`digital`	A4 → THVD1452 high-speed RS-422 driver — Output A link 4 IN	EXT
`digital`	B1 → THVD1452 high-speed RS-422 driver — Output B link 1 IN	EXT
`digital`	B2 → THVD1452 high-speed RS-422 driver — Output B link 2 IN	EXT
`digital`	B3 → THVD1452 high-speed RS-422 driver — Output B link 3 IN	EXT
`digital`	B4 → THVD1452 high-speed RS-422 driver — Output B link 4 IN	EXT

Deploy the firmware

main.cppOpen in Schematik

// Hardware-only AES3 distribution amplifier.
// The AES3 signal path is entirely discrete: no ESP32 GPIO is used.
void setup() {}
void loop() {}