stereo coffee LDR preamplifier

Roughly four years ago I saw my first LDR, or opto-coupler pre-amplifier. I was intrigued by this unique approach to controlling the signal output to an amplifier, but at the time funds were limited, and I didn´t have time for another DIY project. Fast forward to the present and another DIY kit has come my way, the Stereo Coffee LDR pre-amplifier. This time both time and money were at hand, so I took the plunge and ordered the kit from eBay.

The kit comes as two pre-assembled PCB´s, the main preamp board, and a small regulator board. The stock kit comes with RCA plugs installed, but as I wanted to leave my options open,I asked for these to be left out.  All the builder has to do is install the boards in a nice chassis, and provide power. In an effort to keep things as simple as possible I chose to go with a 12V battery power supply with a switch to select between ´play´ and ´charge´.

As the PCB´s are already assembled the build time was spent on preparing the chassis. Once all the cut-outs and holes had been made, assembly took very little time. In total, it took a couple of evenings to complete and test before installing in my main system.


Prior to completing this kit I had been using Khozmo passive preamp in in my main system. This is the modified version with Z-foil resistors, and is very neutral in presentation. When I swapped in the Stereo Coffee preamp I was really surprised at the difference. The presentation was clearer, and the soundstage slightly wider, with placement of instruments and vocalists more destinct. My gut feeling is that this pre-amplifier is very neutral adding little, if anything, to the source. To some this may be perceived as producing a ´clinical´ sound, but I would describe it as a lack of colouration.

The Stereo Coffee LDR pre-amplifier now has pride-of-place in my main system, and I can´t see it being replaced any time soon. If you are happy doing a bit of DIY this kit is a real bargain, and will surprise many when used in a well resolving system.

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3 Responses to stereo coffee LDR preamplifier

  1. A great blog you have here loved the posts you share and will be looking forward for more updates.
    (I’m a bit new to blogging and hope you might wanna check my work too :

  2. Pingback: Innovative handcrafted audio products | stereocoffee

  3. Oliver says:

    Guys I have discovered the LDR preamp and for the first time after 20 years I have replaced my old preamp….fantastic transparency, detail, softness, natural… since 25 years of researchs I have decided to only keep the material that “disapear”… anything that will change the sound or act as a blocker will not stay, the LDR preamp totally disapear, it will stay…

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