Volume Level Adjustment In Monophonic Sound And 4-Sound Generation - Yamaha YMF795 Manual

YMF795

■Volume level Adjustment in monophonic sound and 4-sound generation

The volume level outputted from DAC varies depending on the number of the pronunciation.
When one tone (*) is output from the FM sound source, output voltage amplitude from DAC becomes 0.4125 Vp-p.
When multiple sounds are pronounced at the same time, output voltage amplitude varies depending on phase of each
waveform, but when the waveforms with the same phase are overlapped, it becomes 0.825 Vp-p in 2-tone, 1.2375
Vp-p in 3-tone, and 1.65 Vp-p in 4-tone.
(*: This explanation is made on the assumption that volume adjustment (Total Level of Carrier) of one tone is 0 dB.)
FM
sound source
An assumption of 300 mW output.
Output power of 300 mW can be obtained from the speaker when RL is 8 Ω and a voltage between SPOUT1 and
2 is 1.55 Vrms.
At this time, BTL output amplitude becomes 1.55×2×1.414=4.38 Vp-p, and EQ3 pin is 4.38/3.8=1.15 Vp-p.
(Gain with the speaker amplifier is +11.6 dB= 3.8 times.)
Assurance of volume level in monophonic sound.
"Gain adjustment in the EQ amplifier section" is recommended as a way to assure the volume level in
monophonic sound.
The Gain depends on the resistance ratio between R1 and R2, and Gain is equal to R2/R1.
The Gain of 3 times to 4 times is recommended.
DAC
VREF
SP
VOL
-33-
HP
HPOUT
VOL
EQ1
FM
VOL
EQ2
+
-
EQ3
BTL Driver
+11.6dB
SPOUT1
SPOUT2
R1
R2
RL=8Ω