Advertisement
Design Features
The gain stage is a zero loop-feedback,
balanced single-ended design. It uses a JFET
differential gain stage with power MOS devices
in a class A source follower buffer configura-
tion. This circuit prevents the audio signal from
modulating and from being modulated by the
power supplies and ground. The audio signal
information is effectively isolated from these
sources of signal loss and degradation.
The power supplies use a current source driven
shunt regulator for the gain stage. A separate
power supply buffer is used for the output driver
stage. This supply architecture provides the
stability and isolation of battery power without
the inconvenience and expense.
The power transformer is a custom design, it
provides lower mechanical and electrical
radiated noise than toroidal transformers with
better isolation from noise on the power lines,
mechanical isolation is provided through special
elastomeric grommets. This allows the
transformer to share the chassis with the audio
circuitry without compromising performance.
Extensive mechanical damping is used in the
rigid chassis to minimize microphonic effects
from coloring the signal outputs.
There is over 25,000 mF of capacitance filtering
the raw DC. The first stage of filtering drives
eight (8) individual regulators providing power
to the analog circuits, where audio grade
Page 4
electrolytic and film bypass capacitors
complement the active regulation stages. The
volume control is a precision laser-trimmed
potentiometer used in a unique circuit to
provide balanced level control without
compromising the performance of the balanced
input stage. Over 80 dB of common mode
rejection is maintained over most of the level
control range, this contrasts sharply with the
limit of 40 dB obtained by other balanced level
control methods.
The input controls allow two (2) true balanced
input connections and three (3) RCA jack
connections. The 'Balanced in 2' input
bypasses the tape loop and provides a
minimum signal-path for your primary music
source. The tape output is a RCA output with
an active audio-grade buffer preamplifier to
convert and isolate the internal balanced signal
bus from the tape output.
The elegant simplicity of the balanced single-
ended signal path and gain stage allows the
Tosca to preserve all of the audio signal.
Warm Up
The Tosca's sonic performance will start to
stabilize after approximately forty (40) hours of
continuous power up, and will continue to
improve over several hundred hours of use.
Tosca Owner's Manual
Advertisement
