The OLD
Amplifiers...
A quick overview of the original driver/coupling
transformer solid state power amplifier
used
in the LESLIE® Speaker Cabinet models found in our cross reference
section.
The original power amplifier design uses two (2) areas
of applied DC voltage/current.
1) On some models the primary (driver) side of
the transformer found on the original power
amplifier uses a regulated
+28vdc to +32vdc voltage source established by a single 2N3055
transistor
and bias network to common which is supplied by the storage & filter
capacitors.
This regulator circuit becomes the current source for the
transformer primary stage on
each amplifier. The regulator circuit is part of the
main power supply section.
2) On some models the primary (driver) side of
the transformer found on the original power
amplifier uses a resistive
unregulated +28vdc to +32vdc voltage source established by a
single dropping
resistor which is supplied by the storage & filter capacitors.
This resistor
dropping circuit becomes the current source for the
transformer primary stage on each
amplifier and will pose
several problems as the power amplifier circuits and power supply
age with
time. The dropping resistor is part of the main power supply
section.
3) The secondary (coupling) side
of the transformer found on the original power amplifier
uses the full
unregulated +/- DC which can range from +28vdc to +43vdc positive rail
to common and -28vdc to -43vdc negative rail to common. The transformer
uses two (2)
secondary windings, one in each of the +/- dc rails to
drive two (2) 2N3055 output transistors,
one in each of the +/- dc
rails.
In each model by design both the regulated and the unregulated DC
voltages are supplied
by the same storage/filter capacitors. So the
"available" DC current is always being shared
by both
the primary and secondary windings of the coupling transformer which can
have
adverse effects on overall amplifier performance including more
demand being placed on
the DC power supply.
To sum it up, the
original power amplifiers are basically (2) amplifiers on one circuit
board.
The primary side of the coupling / driver transformer has a (2)
transistor driver circuit that
operates from the dropping resistor or
transistor regulated 28vdc to 32vdc. The secondary
side of the coupling /
driver transformer uses (2) 150watt 2N3055 NPN transistors as the
output
stage. This transformer coupled amplifier design places a heavy demand on
the
DC power supply that will cause numerous problems over time from
age, heat and volume
demands. By todays amplifier standards, it is an
ineffecient way to build a power amplifier!
Our NEW Amplifiers...
A quick overview of our
DTC-4070-PA replacement/upgrade/conversion power amplifier
available for
the LESLIE® Speaker Cabinet models found in our cross reference
section.
The DTC series of power amplifiers are direct coupled transistor
circuits. There are NO
driver or coupling transformers used.
Therefore, our DTC power amplifiers take full
advantage of
all the DC voltage and current available from the original power supply
and in-turn
uses those capabilities effectively in the +/- DC Voltage Rails.
To sum it up, our DTC power
amplifier series requires less current from the DC power
supply. Therefore the DC power supply has a much higher reserve capability
available
when the demand at higher wattages becomes
critical. Plus our DTC power amplifiers
offers a broader range of
frequency response, lower THD and higher gain before
amplifier clipping occurs.
Our DTC power amplifier
series incorporates (2) 180watt NPN TO3 case output
transistors
in order to take full advantage of the original power supply
capabilities. This gives YOU
the awesome advantage to... crank it
up!
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