What is on the board

The TK100 is an NS4168 amplifier on a TinkerBlock board: six pins to the ESP32-S3 along the bottom, a white speaker socket at the top, a solder jumper marked L/R and a red power LED. It comes in the I2S audio kit with a TK101 microphone, a TK103 DAC and a 4 Ω speaker.

Updated 2026-09-245 min readI2S amplifier

One kit, three blocks

The I2S audio kit laid out: the TK103 DAC with its 3.5 mm jack at top left, the TK100 amplifier at top right with six pins on its left edge and a white speaker socket on its right, the TK101 microphone below it with four pins, a teal box printed I2S AUDIO DEV KIT, a 3.5 mm to RCA cable, a 3.5 mm to 3.5 mm cable, and a black rectangular speaker on red and black wires. — The I2S audio kit: TK103, TK100, TK101, two cables and the speaker.

The TK100 comes in one box with two other blocks: the TK101 microphone and the TK103 DAC, plus a 4 Ω 3 W speaker that plugs into the TK100 and two 3.5 mm cables for the TK103. Headers come soldered. The ESP32-S3 and jumper wires are not in the box.

Six pins, one socket

The TK100 from directly above: a white two-pin socket at the top between AUDIO + on the left and AUDIO - on the right, the eight-legged chip in the middle between two round LEGO holes, a small jumper marked L/R at the lower right, I2S AMPLIFIER up the right edge, and six right-angle pins along the bottom printed GND, 3V3, LRCLK, BCLK, DIN and CTRL. — Speaker at the top, ESP32 along the bottom.

Pin	Goes to	In this book
GND	GND	GND
3V3	the chip's supply, through a ferrite bead	3V3, never 5 V
LRCLK	chip pin 2, through 22 Ω	GPIO 16
BCLK	chip pin 3, through 22 Ω	GPIO 15
DIN	chip pin 4, through 22 Ω	GPIO 17
CTRL	chip pin 1, through 22 kΩ	GPIO 18, driven HIGH

The 22 Ω in each I2S line softens the clock edges, and a ferrite bead in the supply keeps the amplifier's switching out of the rest of the circuit. Neither needs anything from you.

A tour

What is on the board

Six pins to the ESP32

Part

Worth knowing

22 Ω in each I2S line

Six pins to the ESP32. Four of the six carry signals, and CTRL is the one people leave off: without it HIGH the chip stays switched off.

The speaker socket is a white two-pin socket with 1.25 mm pitch, between the labels AUDIO + and AUDIO -. Neither wire is ground, which Both wires move explains.

The L/R jumper is two half pads next to CTRL. It ships open, and it only matters when two TK100s share the same three wires to make stereo. CTRL: on, off, left or right works out what it does.

The power LED is red and lights whenever 3.3 V arrives. It is not a sign that the chip is on.

When it does not work

The power LED is on but there is no sound.

The LED is wired to 3V3 and lights whenever the board has power. It says nothing about the chip, which stays off until CTRL is driven HIGH. Check CTRL first.

Which way round does the speaker go?

Either way plays. Neither speaker wire is ground, so there is no wrong way for a single speaker. What matters is that nothing else touches either wire: not GND, not another board.

Do I need to solder anything?

No. The header comes soldered and the kit's speaker plugs into the socket. The L/R solder jumper ships open, which plays the right channel, and the book's sketches play on either setting.

Can I use my own speaker?

Yes, a bare speaker of 4 or 8 Ω, on a plug that fits the 1.25 mm two-pin socket. Something rated for about 1 W or more is comfortable on 3.3 V.

Alongside this page

An LED and its resistor ESP32 pins you cannot use

Where this goes next

What LRCLK, BCLK and DIN carry, and why the chip plays only one channel.

Three wires, one channel →

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