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1. Basic information
1.1 Mechanical construction & supply
The case is fully made of aluminium. The audio-connectors are all gold plated to minimize electrical losses
and provide long lasting perfect contacts.
The PA3.2's power supply consists of an oversized toroidal transformer with minimized magnetic stray field
and 10.000 µF of capacitance. In the A3.2 / A5.2 a switch mode power supply delivers clean, hum-free
electrical energy for the analogue sections of the preamplifier. All voltages are additionally buffered by large
capacitors directly in the circuitry where they are needed. The power amplifiers are fed by a separate switch
mode power supply (A3.2) respective two independent switch mode power supplies - one for each channel
(A5.2) Thus independently of the demanded output power the power amplifier has no influence on the
preamp.
1.2 Preamplifier
The input circuits act extremely fast and use special semiconductors for exact and nearly noise free sound
reproduction. SMD technique allows a very compact circuit layout and thus extremely short signal paths.
The volume control is done by highly precise integrated circuits. They allow setting in 0,5 dB steps and their
channel balance is better than 0,05 dB. All this provides an absolutely precise, musical sound reproduction
from lowest to highest listening levels.
If you whish to correct the frequency response at low listening levels or to have more or less treble or bass,
you can activate the sound processor and set the frequency response. For linear reproduction the whole
circuitry is removed out of the signal path by relays and has absolutely no influence.
The preamp section has one balanced XLR input and five RCA-Cinch inputs. Additionally there are three
slots for plug in cards: one phono card, one tuner card and a digital card with three digital inputs.
One fixed level output for recording and a processor in/out for connection of equalizers are provided. The
two preamplifier outputs (RCA-Cinch and XLR) are driven by powerful output stages and can easily handle
longer cables with high capacitance.
1.3 Power amplifier (A3.2 and A5.2 only)
A3.2 and A5.2 use for each channel a separate powerful and efficient digital class-D amplifier. These
amplifiers have an analog feedback loop from output to input. This ensures a nearly load-independent
frequency response and a very good damping factor.
Further highlights are very low output noise, low distortion and an extremely good efficiency. Even when
delivering peak power levels to the speakers they deliver over 90% of the supplied energy to the speakers
and thus produce nearly no heat.
1.4 Tube preamplifier stage (PA5.2, A5.2T only)
These amps equipped with a tube stage in the preamp section. We use one double triode for each channel.
The triodes are operated fully balanced. They operate with grounded gates and are fed via the Cathodes.
This circuit design ensures very quick reaction without sound degrading feed back. The tubes are heated
with about 2 Watts of power. This ensures a very long life and constant characteristic over the whole lifetime.
Thanks to the wide operating range and the balanced operation mode PA5.2 and A5.2T offer a very good
dynamic performance and even a further step ahead in musical quality.
The high voltage for the tubes is generated by a separate power supply which is fed by a precisely regulated
DC voltage. A 300 Hz sine generator followed by a power stage and a toroidal transformer generate the
regulated high voltage. This power supply operates fully independent of the unstable mains voltage and thus
the tubes can always operate at a stable bias point.
