LM1875 Amplifier Kit

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The LM1875 kit was developed as a lower powered alternative to the LM3886 kit. The kit provides between 20-25w of power, depending on the output impedance of the speakers. The kit is available now as a pre-order item, with
the first batch of kits shipping out around the second week of July. For the pre-order special, an extra stereo pcb will be provided with the purchase of a stereo kit.

Assembly thread for the LM1875 (manual coming soon)

Pictures of prototype amp:

pic1 pic2 pic3 pic4

Suggested transformer for stereo kit: Avel Lindberg 2x18vac transformer
LM1875 Stereo Kit Contents
1 LM1875ST PCB set, consisting of 2 amplifier and 1 power supply boards.
Components for amplifier boards
2 LM1875T
4 22 kohm 0.5w compact metal film resistors
2 1 kohm 0.5w compact metal film resistors
2 2.7 ohm 2w metal film resistors
4 47 uf 50v Panasonic FC
2 2.2 uf Panasonic film
2 22 uf Panasonic Bipolar
6 0.1 uf film caps
Components for power supply board
2 1500 uF 50v Panasonic FC Capacitors
4 0.1 uf film caps
4 MUR860 On Semiconductor Diodes
2 1 ohm 2w metal film resistors
1 blue LED
1 10 kohm 0.5w compact metal film resistor
Amplifier board designations:
picture of front of board

picture of back of board

R1 not used (optional resistor to ground before C1)
R2 22k (input to ground resistor)
R3 1k (gain resistor, gain = 1 + R4/R3)
R4 22k (nfb resistor – on bottom of pcb)
R5 2.7 2w (optional – zobel network)
R6 jumper (optional resistor between input ground and output ground)
C1 2.2µF (optional input capacitor)
C2 22µF bipolar (optional)
C3 0.1µF (power supply decoupling)
C4 47µF (power supply decoupling)
C5 0.1µF (power supply decoupling)
C6 47µF (power supply decoupling)
C7 0.1µF (optional – zobel network)
Power supply board designations:
picture of front of board

picture of back of board

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R0 10k (series resistor for LED)
R1,R2 1ohm 2w (optional “snubber” network capacitors)
C1,C2 1500µF (main power supply caps)
C3,C4 0.1µf (power supply decoupling)
C5,C6 0.1µf (optional “snubber” network capacitors)
D0 blue LED
D1-D4 MUR860

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