Summary of "Getting Max Power from a TPA3255 Testing ZK3002 at 8 ohm and 4 ohm #thermalcamera #classdamplifier"

Overview / purpose

Bench power test of a Wooi Audio ZK3002 (ZK30002) stereo amplifier module that uses the TI TPA3255 Class‑D amplifier IC.
Goal: find sustained maximum continuous power (bridge‑tied load / stereo) while monitoring distortion and temperatures; check how well the on‑board heat sink and fan handle continuous high output.

Amplifier IC: TI TPA3255 (mounted under a heat spreader beneath the large heat sink).
Operating modes:
- Stereo (two bridge‑tied loads).
- Switchable parallel/mono (parallel bridge‑tied / monoblock) via a silk‑screened switch.
Front panel / controls:
- Input connector, on/off switch, gain pot (electronic/digital volume control).
- Mode switches for auto/manual fan and parallel mode.
Preamp / input stage: M62429 digital volume IC and JRC 2068D dual op amp.
Power connector and limits:
- Center terminal power input.
- Board components/capacitors make the board conservative to about ~50 V (TPA3255 IC itself can tolerate slightly higher voltages).
Passives and layout: polymer (low‑ESR) caps, electrolytic caps, inductors, clear silk‑screened soundboard layout.
Cooling: large aluminium heat sink with a quiet fan; fan has auto/manual behavior.

Signal source:
- Siglent UTG1042X function/ARB generator.
- A cleaner dedicated sine generator used later for THD checks.
Probing and distortion measurement:
- Differential probes (MDP‑1500 and x50/x500 probes).
- Keithley 2015 distortion meter (THD). Note: the generator contributes some distortion.
Power supplies:
- Early tests used bench supplies (32 V tests).
- Small 48 V / 5 A module supply (current limiting).
- Larger Xantrex/Zantrex supply (XPD60‑9) to reach ~49–49.5 V at higher current (7+ A).
Loads:
- Banked resistors (4 Ω and 8 Ω power resistors) used as loads; resistors reached high surface temperatures during tests.
Thermal imaging and photos were taken throughout testing.

Voltage limitation:
- Module is effectively rated to ~50 V; testing kept the supply below this (≈48–49.5 V).
4 Ω bridged (per channel):
- Achieved ~156 W RMS per channel (≈312 W total) continuous sine at ≈48–49 V before significant distortion/clipping.
- Fan ran and the module stayed thermally controlled at these levels.
8 Ω bridged (stereo) equivalent:
- Roughly half the 4 Ω power — around ~78 W per channel (8 Ω equivalent reported).
Efficiency and heat:
- High efficiency observed (~95% noted); only a small percentage of input power converted to board heating.
- Heat sink + fan kept module temperatures modest at test loads.
Thermal notes:
- MOS/chip area temperatures remained manageable.
- Load resistors reached very high temperatures (one measurement >140 °C).
- Fan auto on/off behavior observed in steady state.
Distortion:
- THD increases as output approaches maximum.
- Visible waveform “spikiness” appears around ~27–28 Vrms input drive (near clipping/flatline).
- Some measured THD originates from the generator and probing; tester avoided sustained clipping by backing off before flatline.
Power‑supply limits:
- Early 5 A power supplies limited achievable power.
- Larger supplies enabled higher output but the board’s ~50 V rating was respected.

The ZK3002 TPA3255 module with a large heat sink and quiet fan can deliver sustained high continuous RMS power (~150+ W/channel into 4 Ω bridged at ~48–49 V) without thermal shutdown when supplied with sufficient current.
For sustained maximum output, use a power supply capable of adequate voltage and current. The tester suggested ~60 V @ 10 A capability for more headroom, though the board itself is conservatively rated to ~50 V.
The board’s use of polymer caps and good magnetics is positive; nevertheless respect the board’s stated voltage limit even if the chip can tolerate slightly more.
For higher total power, consider parallel/monoblock configurations (module supports parallel bridging) but ensure appropriate cooling and power supply capability.
Measurement caveat: generator and some probes add distortion/noise; using a cleaner signal source improves THD measurement accuracy.

A quick mono/parallel bridge test video (monoblock).
More formal performance plots (Bode plots, THD vs. power curves) using measurement software (QuantAsylum or similar).

Speaker / tester: Eddie Aloo (kissanalog.com / YouTube).
Hardware / parts: Wooi Audio ZK3002 (ZK30002) module, TI TPA3255 chip, M62429 digital volume IC, JRC 2068D op amp.
Test equipment: Siglent UTG‑1042X generator, Keithley 2015 distortion meter, differential probes (MDP‑1500, x50/x500), Xantrex/Zantrex supplies (XPD60‑9), various bench supplies (UDP 1306C, IT 6721, UT8805E).