MAX9708/MAX9709 25W/50W class D - measurements

The version 3 of the MAX9709 on the testbench.

Measuring instruments:

• PC/FFT Analyzer
• Phonic FIREFLY 202 easyUSB 24 bit/96 kHz
• Hantek DSO5202B
• Power supply 0-30V

Applies to the measurements:

-3dB = 12W
-6dB = 6W
-9dB = 3W
-12dB = 1.5W
-15dB = 750mW
-18 DB = 375mW
-21dB = 187 5mW
-24dB 93 75mW =
-27dB = 46 875mW
-30dB = 23 4375mW
-33dB 11 72mW =

Output signal at UB = 15V, 22dB gain and 8 ohm/47uH load without input signal:

FFT

Reference measurement of the sound card (FFT) loopback:

Output signal at ~ 10µW output power (1 kHz):

Output signal at ~ 10mW output power (1 kHz):

Output signal at ~ 10mW output power (250 Hz 8 kHz cross-modulation):

Output signal at ~ 10mW output power (1 kHz) to real speakers (Visaton BG20) and UB = 20V:

Frequency response

Frequency response measurement of reference:

Frequency response MAX9709 with 8 ohm/47uH measured about 8 ohm:

Frequency response MAX9709 with 8 ohm/47uH measured about everything:

Frequency response TA2024 comparison with 8 ohm/47uH measured over all:

Gain

Comparison of the gain setting (22dB/36dB) on small Panasonic shelf box with 250 cm cable (2 × 0.5 mm²)

Output signal at ~ 10mW output power (1 kHz) and gain = 36dB:

Output signal at ~ 10mW output power (1 kHz) and gain = 22dB:

Output signal at ~ 100mW output power (1 kHz) and gain = 22dB:

Output signal at ~ 100mW output power (1 kHz) and gain = 22dB, alternatively with 15 m 2x4mm 2 connection line:

THD

At THD UB = 15V with 8 ohm/47uH measured (100 Hz):

At THD UB = 20V with 8 ohm/47uH measured (100 Hz):

At THD UB = 20V with 8 ohm/47uH measured (1 kHz):

Comparison of THD vs. frequency at UB = 15V and 20mW output level, 22dB (green) 36dB (blue) = gain:

Transient response

Rectangle/pulse response at UB = 15V with 8 ohm/47uH:

Rectangle/pulse response at UB = 15V with speaker BG20:

EMI/EMC/RF measurement

RF measurement to EN61000-6 with broadband antenna 3 meters away from 30 MHz - 1 GHz, RMS/AVG, 40 cm cable, 1 channel, 10 ohm load:

Skillful modulation the MAX9708/9709 achieved very little dissipation, comparing low/high:

Many thanks to "alfsch" by d amp.org for the measurements.