Slide # 40
Models:
SA-PT660
SA-PT760
SA-PT960
SA-PT1060
SH-FX67, 85
Outline
Wireless
Mech
Pwr Supply
Protection
Audio
Audio – Speaker Output Waveforms
No Audio
@ spk term
Music or Voice Audio
@ spk term
Background sine wave is modulated with
voice audio that averages above and
below the 0V center line (PAM).
Digital Scope snapshot at the Speaker Terminals
Spk Terminal Output = background sine wave at
1.4Vp-p @ 375kHz. Duty cycle = 50%
Average spk DC voltage = 0Vdc
Same output with or without speakers.
Normal “RF” waveform at the speaker
terminals even when there is no sound!
Typical voice waveform
at the speaker terminals
There is a constant 1.4Vp-p minimum signal
with the digital (PAM) audio.
PAM = Pulse Amplitude Modulation
Units with a digital power output IC always outputs a sine wave at the speaker terminals
Output IC is ON * but may be muted or
no audio is input.
* Output ICs can be turned off from the mute
input. 5V = norm, 3V = mute, 0V = Off.
