Accuphase class-A stereo power amplifiers have a longand distinguished history, since the P-260 launched in
1979, we have continued to develop them up until today.
The new A-48 is the latest class-A stereo power amplifier
and the succession model of A-47.
A-48 achieved the further low noise performance andsuper high damping factor that are in the class of its own,with inheriting the ultimate technology features of the A250, the flagship class-A monophonic power amplifier.
Accuphase also offers the new ideas to prevent thespeaker short-circuit accident for a customer to use inrelief.
Evolved A-48 will surely attract the customers with its
pure class-A sound.

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A-48 newly applied a top plate made of brushed
aluminum with a hairline finish. It demonstrates a level ofdedication and hands-on craftsmanship that pervades
every aspect of this product.
**The former model A-47 used the velvet-coated iron topplate.
Needle power meter with indication range to -50dB isable to move even at the small volume level less than 60dB.

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Strong power supply with a massive special made highefficiency toroidal transformer and two large 60000μF
special made filtering capacitors are installed.
The capacitance of capacitor is reinforced compared tothe former model.
**A-47: 56000μF

3The continuous average output power(rated outputpower) is 45W into 8Ω load.
However, its actual maximum output power is bigger,
saying 102W into 8Ω and 438W into 1Ω load.
**Output power is as same as A-47.

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The performance highlights of A-48 are “Ultra low noise”
and “Super high Damping Factor”.
The A-48 features the latest instrumentation amplifier
topology. It consists of a complete balanced input
amplifier block and a power amplifier block.
The balance input amplifier block is related to the noise
performance and the power amplifier block is related tothe Damping Factor.

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The former model A-48 has the excellent noiseperformance.
However A-48 achieves even 1dB higher guaranteed S/Nratio than A-47.
A-47 guarantees, S/N ratio: 116dB @Maximum-gain

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The output noise is reduced by the fully discreteconfiguration amplifier circuit which any ICs are notinstalled on the signal paths.
It is exactly same circuit configuration as Class-A Stereo
Power amplifier A-75.

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A-48 has the guaranteed 800 of Damping Factor.
It is 33% higher than the former model A-47.
**Damping Factor:
A index of speaker driving ability.
Higher Damping Factor amplifier has higher speakerdriving ability.
D.F. = 8Ω / Output-impedance

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The output impedance is decreased by 6 parallel push-pull
final stage arrangement of MOS-FETs.
Circuit configuration of the power amplifier engine is as sameas Class-A Stereo Power amplifier A-75.
A-48 features the new power MOS-FET device which isheavy-duty and has the large rated current characteristic.
**Current capacity of power MOS-FET
A-47’s MOS-FET(Toshiba): 10A
A-48’s MOS-FET(Fairchild): 33A

A-48’s MOS-FET

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Remote Sensing is the technique to lower the output
impedance of amplifier by the negative feedback withsignal sensing from nearby the speaker terminals.
Balanced Remote Sensing is the technique to make theoutput impedance even lower by both the signal sensing
and the GND sensing, that is the negative feedback of
GND level.
Not only Damping Factor, but also Total Harmonic
Distortion and Intermodulation Distortion are all improvedby the Balanced Remote Sensing.

10Mechanical relays are the common components for speakerprotection.
But, As the contact resistance of mechanical relay is higher
than people think, Accuphase has chosen the MOS-FETswitch instead of conventional mechanical relays for speakerprotection.
Thanks to this MOS-FET switch, the Damping Factor,
reliability and sound quality are all improved.
A-48 features the new MOS-FET device for this switch whichhas very low on-resistance.
**On-resistance of MOS-FET device
A-47’s MOS-FET: 1.9mΩ
A-48’s MOS-FET: 1.0mΩ
A-48 employs carefully-selected very low impedancecomponents such as the large speaker terminals and so on.
Making signal paths thick and short also helps attaining thelow impedance.

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To enhance the further product safety and reliability, A48 improves the protection circuit on Power amplifier
section.
・Newly-developed protection circuit
Over current protection circuit using photo-coupler isapplied, it does not affect the sound quality at all.
・Temperature-sensor
Temperature-sensors which detects the heatsink
temperature are installed on the heatsink(2 sensors on aheatsink). Thanks to this, the unit accurately ascertains
the high temperature alarm in power amplifier section.
**When these protection circuits are activate, the unit
completely interrupts speaker output and makes thepower meters flash to indicate an abnormal condition.

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