Here's
a Leach Amplifier based on 2SC5200 and 2SA1943 output power transistors
that can provide up to 700W of power. The mechanical design is
relatively simple, the transistors are placed on the two cooling
profiles with a height of 66 mm, width 44mm, overall length 260mm. They
are turned against each other Thus, from the cooling tunnel. Coolers are
attaching the nylon backing which allows the assembly of transistors
without washers, and thus better transfer of heat. DPS amplifier is at
the top of the tunnel and the transistors are soldered from the bottom
of PCB.
700W
Leach AmplifierAdjust the amplifier power 700W looks easy, but we must
not forget that the change in forcing transistors, the entire
re-engagement of frequency offset. It is necessary to modify the current
insurance policy which serves to protect the final transistors. Their
tendency to be allowed to keep the transistors in the SOAR
characteristics. First it was necessary to calculate all the necessary
resistors and then measured to verify the accuracy of the calculations,
it is managed with satisfactory results.Peripheral changes needed for it
to be able to consistently amplifier to supply power.- First you need
to replace the 2k2 resistors in series with the LEDs at Zenerovými
resistors with higher wattage. Suffice 1/2W resistors, power loss at 80V
+-based 1W.- Then was traded 1k2 resistor in the feedback resistor at
620 ohms. Which is the original gain has doubled, so now is the overall
gain amplifier 40 and the maximum excitation is sufficient to 1V rms.-
Předbudiči transistors were replaced by stronger MJE15032/33 because
KF467/470 are allowed collector current 20mA- At the exciter output
stages are used the same transistors as the output stage.- Number of
terminals of transistors has been increased to eight pairs- It had to
occur to compensate for the excitation level by adding a capacitor 10pF
to 47pF + 22K member. This led to a slight "slow" amplifiers, but this
did not affect the resulting parameters. This capacity is tuned
precisely for this type of terminal transistors 2SA1943/2SC5200. With
that it is a minimum value at which the amplifier operates stably
without overshoot at the rising and falling edges of the square.- The
last adjustment, the adjustment terminal current protection transistor.
The SOAR transistor characteristics shows that the maximum allowable
collector current when the voltage of 1.5 A is ideal for cooling, so
it's actually less. Therefore, the current protection is set to 12A,
single-arm. This copy protection SOAR transistor characteristics.
Short-circuit current is about 6 A which is about 075A per transistor.
This is far below the SOAR characteristics.The mechanical design is
relatively simple, the transistors are placed on the two cooling
profiles with a height of 66 mm, width 44mm, overall length 260mm. They
are turned against each other Thus, from the cooling tunnel. Coolers are
attaching the nylon backing which allows the assembly of transistors
without washers, and thus better transfer tepla.DPS amplifier is at the
top of the tunnel and the transistors are soldered from the bottom of
PCB.
Technical parameters:
Output: 680W/2R, 450W/4R, 260W/8R
Minimum speaker impedance: 2R
Bandwidth: 10-180 000Hz/-3dB
Maximum permissible voltage: max + /-80V
Fusing end amplifier: 2x 15A / F
Late connection: approx 1.5 sec
Input sensitivity for maximum excitation: 1.1 V
Slew rate: 35V/us
