DIY: LM3875 gainclone amplifier build

Few years back, I have built a BrianGT’s ( LM3875 based gainclone amplifier. It had one small 80VA trafo, crappy enclosure, crooked volume pot and while it sounded OK, it never passed WAF (wife acceptance factor) to make its way into the entertainment center. So little over year ago, I have decided to upgrade it. I have ordered nicer enclosure from Ebay, put it in the closet with other parts from already disassembled chipamp and forgot about it. Few months back when looking for something in the closet, I have stumbled upon the case and the parts and decided to finish the project.

Since I had to drill new holes and redo the wiring, I have decided to do few upgrades. I have added second trafo and another power supply board with full-wave rectifier. The kit came with small 10uF smoothing capacitors which were upgraded to 10,000uF Nichicons (one for each rail). Old volume potentiometer was replaced with Alps and new case got two power LED lights (one for each channel).

As with all the kits, the most time consuming part is the wiring and general assembly so it took me few evenings to do everything. Finally, this past weekend the chipamp gainclone was reborn. Here are some pictures:

DIY LM3875 gainclone amplifier build DIY LM3875 gainclone amplifier build DIY LM3875 gainclone amplifier build

For those interested more in sound than the build, I have to say that I am impressed. LM3875 based gainclone uses few parts and sounds great. The sound is uncolored since there are no tone controls. To my ears (and they are not very well trained) the sound is clear in the highs and mids.  The lows are adequate and were able to move the 10″ woofers in my Thiel speakers. I have to test this amplifier with the EPI 100s that I have stored away as I would think they would be a better match. Anyway, this now goes as a permanent addition to my entertainment center since the sound and looks are great.

1 thought on “DIY: LM3875 gainclone amplifier build

  1. Jon Reply

    if you check the link below:

    This link below is the older version:

    If you can type this in google “ttester_eng104k.pdf” you can dowload the manual. it is meant to be very accurate.

    If you connect test leads you can test components directly on circuits, even Capacitors (but discharge first) using esr.


    1. Resistor:0.5Ω-20MΩ
    2. Capacitor:30pF-20000uF (all types) uses ESR to find ohms.
    3. Transistors: finds bce on pins npn pnp and also types and condition & more.
    4. Inductors measures H to Mh
    5. Diodes, shows value, leaks, identifies direction of voltage ie both ways (failed) one way
    ok etc
    5. Bridge rectifiers
    6. Voltage regulators

    I think it can do more.. very clever device and saves you tremendous time diagnosing faults.


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