This is assembled board, adjusted and tested amplifier boards of the classic JLH( John-Linsey Hood) 1969 class A amplifier. While JLH 1969 is a simple design, it is still one of the best transistor amplifier.
Model: JLH1969 Name: Amplifier Board 1. Double-sided, thick copper PCB. This one is doubled-sided so the copper pad durability is greatly enhanced by plated-through hole ( PTH) process. 2. Hermetically sealed metal casing transistors used on both small signal and power stage. 3. High quality electrolytic capacitors. 4. High quality solder with silver content is used in soldering. 5. ERO film capacitors for audio coupling. 6. Thick and heavy aluminum plates already mounted on the board( as in the pictures) for easy to interface with heatsink.
1.Operating voltage: DC 12V-35V (corresponding to 9-26V transformer) 2.Output sound power: approx 10-15W 3.It can be pushed 3-8 inches, 120 watts of power bookshelf box, full-range boxes. Sensitivity to be higher than 83db 4. Adjustable quiescent current between 0.3-1.8A, recommended 1.2 Ann (radiators need more than 0.7 kg)
Adjust the midpoint / quiescent current method: midpoint: 1. Select the universal table’s 10A 2. black pen -GND, red lead -TP1 3. Adjust the adjustable resistance KT1 (supply voltage 1/2) Current: 1. Select universal table’s 10A 2. Loosen the screws of VCC supply, pull out the wires 3. One pen connected to the pull out wire, the other pen connected to the screw of terminals, which is a measure of the current (equivalent to remove the VCC line of 1969 board, replaced with an ammeter) 4. Adjust the adjustable resistor KT2 changing the current
1 x JLH 1969 class A amplifier Board (Left Channel)