The Gainclone. Introduction: Background Info: Construction Notes. Introduction. The model Gaincard from 47 Laboratories is a 25 Watt stereo amplifier. Check for Samples: LM The LM is a high-performance audio power LM to reduce the effects of PCB trace resistance and inductance. PCB for 56W Audio Amplifier using LM HiFi Amp. For LM IC. High quality FR4 double-sided, plated-thru and tinned holes, with conformal coating.

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LM product folder and LM Salim Khan 22 May Reply. How to builds This projects is easy to builds because to adjust anything and few parts as Figure 4 and Figure 5.

Figure 3 the schematic diagram. The input impedance of the amplifier is determined by resistor R1. Increasing power output into an 8-ohm speaker is trickier. If you do it right the amplifier is completely quiet but grounding can be a problem.

The Gainclone

This capacitor prevents large DC currents from being sent to the speaker when the input connection is disconnected. The only donwnside is it is only capable of driving an 8-ohm speaker.

Undistorted volume levels were also much better. The PCB file is avaliable in Eagle format, ready to print.

For only 56W, the sound is, as I’ve said, fantastic, and sounds like much more than 56W. Star-grounding will help you to avoid ground loops, which may lead to severe problems with hum and noise in audio amplifiers. To connect the output of the amplifier to the speaker output terminals, a thicker solid or stranded wire should be used while high-quality shielded cables should be used pccb input signal wiring. Currently, I’m not done with the circuit or board for that yet.


The RCA input ground can go to the base of the attenuator, rather than R2. LM chip is used.

LM – Power amp kit

Figure 1 The amplifier schematic is shown in Figure 1. In general, though, the capacitors affected the sound more than the resistors, the diodes more than the capacitors, and l3m875 transformer most of all. It is not a bad idea to add a switch on the rear of the amplifier, whereby the star i. Mute switch is a mechanical switch of the output.

It is understood that Kimura removed the film bypass caps C3 and C4, and R1 on the circuit will be replaced by the stepped lm3785. Diodes should be rated to at least 5A. In short, no excuses. Soft recovery types are probably the best bet. Power cord is captive four pin molex, one per channel. Furthermore, diodes D1, D3, D6 and D8 should then be omitted. Power supply parts list: This image is to be used as a guide while assembling.

Note that C1 must be non-polar. I started by setting up a prototype using the LM chip with regular EI laminated transformers.

LM3875 Gain Clone Amplifier Project

The amplifier schematic is shown in Figure 1. LevHyp 19 May Reply. I also have llm3875 much the same short length of signal path and feedback loop, the latter obtained by soldering R4 directly across the chip leads. I preferred the two big bridges, which sounded more open and powerful, but clearly there is room to experiment.


The lm8375 can be used in the inverting mode, as well. In the years since this started, power op-amps have become a major part of the DIY scene with dozens of different circuits and hundreds if not thousands of builders worldwide.

Gainclone LM PCB – Electronics Projects Circuits

Separate power supplies can be used for each channel if desired. I tried replacing my two 50A bridge rectifiers with 4 discrete diodes. I conclude from my experiences that carbon film is the right choice for the R2-R4, AB carbon composition sounded too noisy and fuzzy, metal oxide too grainy, and from a different circuit metal film too, uh, metallic and zingy.

I used carbon film resistors for R2-R4, metal film for R1, and metal oxide for R5. This chip delivers unbelievable quality, especially for it’s low power levels. This article focuses on a tried and true low-power amplifier 30W with the IC LM, originally intended for the design and testing of active speaker systems.

Separate position attenuators for each channel. Here is how to wire the board for 4-ohm speakers: Therefore, you would want to choose an R3 value greater than 4.