SM-SX100
– 17 –
3-2) The feature of 1-bit amplifier
As described above, the amplification principle whose viewpoint is different from that of the existing analog amplifying
circuit assures S/N in the audible band, thus achieving the audio amplification which has the wider band.
Moreover, the operation which converts the voltage through the switching operation approximately halves the power
consumption during the ordinary operation in comparison with the existing analog amplifier, thus reducing the heating
amount of the amplifying section to approx. 1/5. In addition to the highly faithful replay of the audio source, it achieves both
energy saving and compactness/high power at the same time.
On the other hand, an countermeasure to suppress the noise in the power amplification with the switching operation
becomes inevitable. Particularly against the power line noise and unnecessary radiation, the countermeasure is taken from
both sides of the circuit (minimization of coring and circuit loop) and the structure (double shield of steep plate and copper
plate), thus clearing the technical standard of the electricity operation.
Moreover, the input terminal unit is provided with the originally specified 1-bit signal input terminal in addition to the three
analog systems and four digital audio interface systems. This terminal is provided to be connected to SACE player of our
company which will be put on sale in near future, being specified to transmit the 1-bit signal after the player is mutually
recognized as the countermeasure against the illegal copy.
The analog signals of the three systems are selected with the relay circuit by the function, and the attenuation level is then
set with the volume. This signal is connected to the analog input pin of the 7th order
modulation 1-bit signal generation
circuit, and the aforementioned "signal process of 1-bit amplifier" is applied.
The digital signals (multi-bit signals) of the four systems are input in the format of the audio interface but the sampling
frequency corresponds to 32 kHz/44.1 kHz/48 kHz. These plural sampling frequencies are converted to 44.1kHz by
"sampling rate converter circuit". This signal is farther oversampled, and "64fs 1 bit signal" is generated by "multi-bit to 1
bit conversion circuit".
Since the 1-bit signal which is output includes the analog information coded in the original digital signal, the analog sound
volume level can be adjusted by controlling the wave height value of the 1-bit signal itself with the volume.
The signal is differentially connected to the digital input pin of the 7th order
modulation 1-bit signal generation circuit,
and the aforementioned "signal process of 1-bit amplifier" is applied like the analog signal.
From the special terminal of SACD, the 64fs clock of the SACD player side is supplied.
As aforementioned, the analog sound volume level can be adjusted by controlling the wave height value of the signal itself.
The signal is differentially connected to the digital input pin of the 7th order
modulation 1-bit signal generation circuit,
and the aforementioned "signal process of 1-bit amplifier" is applied like the analog signal.
