YMU757B Datasheet, PDF (30/43 Pages) YAMAHA CORPORATION – MA-1C

YMU757B
One sound and volume level adjustment in 4 sound pronunciation
The volume level outputted from DAC by the number of the pronunciation is different.
When 1 sound (*) is outputted from FM sound source, output voltage amplitude from DAC is 0.375Vp-p.
When more than one sound is pronounced at the same time, output voltage amplitude varies in the phase of each
wave shape.
But, when the wave shape of the same phase piles up, it becomes 0.75Vp-p by 2 sound, 1.125Vp-p by 3 sound,
1.5Vp-p by 4 sound.
(*: The volume adjustment (Total Level of Carrier) of 1 sound is being explained with the premise of 0dB.)
FM sound
DAC
HP
VOL
FM
VOL
VREF
+
SP
VOL
BTL Driver
+11.6dB
HPOUT
EQ1
R1
EQ2
R2
EQ3
SPOUT1
SPOUT2
RL=8Ω
An assumption in 300m W output.
Output power from the speaker is 300mW when RL is 8Ω and a voltage between SPOUT1 and 2 is 1.55Vrms.
BTL output amplitude at this time becomes 1.55×2×1.414=4.38Vpp, and becomes 4.38/3.8=1.15Vpp with the
EQ3 terminal.
(Gain with the speaker amplifier is +11.6dB= 3.8 times.)
Securing a volume level by one sound.
Gain adjustment in the part EQ amplifier is recommended as the way of securing a volume level by one sound.
Gain depends on the resistance ratio of R1 and R2, and it is GAIN=R2/R1.
Gain to recommend is about four times from three times.
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