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.

Module / hardware features

• 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.

Test setup / measurement gear

• 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.

Key results / measured behavior

• 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.

Practical conclusions / recommendations

• 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.

Possible follow‑ups the tester mentioned

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

Main speaker / referenced hardware and test equipment

• 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).