Primare AB • Renvägen 1 • SE - 35245 Växjö • Sweden • Tel +46 470 729215 • www.primare.net
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REVIEW: I22 INTEGRATED AMPLIFIER AND CD22 CD PLAYER
Technology By Image
Internal view of the I22 without the card
01
Switch-mode power supply card developed by Primare. These power supplies are of the
PFC (Power Factor Control) type that control the mains for a pure sinusoidal signal, of the
same frequency and without phase shift with respect to the power (avoids drawing more
power than is necessary, unlike that produced by other types of power when a very strong
spike in current causes a phase shift). Separate power supplies for power stages, those for
pre-amps, those for standby
02
Pre-amp card (optional DAC digital module removed)
03
Source selection: switching by relay
04
Buffer levels by op amplifiers
05
National Semi Conductor LM 1972 volume control circuit (switched resistance
microphones)
06
74HC595D circuit register (asynchronous with a clock) that syncs the conversion stage of
the PWM signal with the output stages in class D
07
LVC 244 circuit buffer driver
08
Power stage card in class D for switching. The digital signal feeds each channel’s MosFet
power transistor (International Rectifier IRFI 4212H double transistors in each, designed
specifically for Class D amplifiers). The pattern of this Class D amplifier was made and
developed by engineers from Primare, it is called Ultra Fast Power Device (UFPD). It
adopts a configuration circuit with gain adjustable to frequency and power requirements.
This arrangement is stable. The usual distortions in the treble are absent
09
Integration and filtering with choke and condenser
10
Switching relay
11
Output chokes to prevent the risk of over modulation.
