LM1875 Gainclone Amplifier With First Watt B1 Buffer Pre-amplifier

I like building amplifier because it is fun. Anyway, we are doing this hobby because it is all fun. But what I am trying to say is, I can planning something that I want to make for the next project and when the result is beyond my expectation, this is the magnet to dive into this hobby deeper.

This is happens when I plan to combine the First Watt B1 buffer pre-amp with the Gainclone LM1875 amplifier. I like sound of the LM1875 amplifier and I also like the idea behind the First Watt B1 buffer pre-amplifier. So how if they are combine?

A brief about this LM1875 amplifier is I think the most relaxing sound I've ever built so far. The music presentation is very mellow and warm, at the same time it can be deliver fast and dynamic enough.

The First Watt B1 buffer amplifier is the simplest pre-amplifier design. It is using 2 JFET 2SK170 per channel and no feedback in the design. The goal when using this B1 is as per stated on the First Watt manual is to get the impedance matching between the input to the amplifier. This will become an integrated amplifier by combining both circuit.

Building the amplifier like this is not always necessary involve with the hi-grade components. Like I will do it right now, it is using China made toroidal transformer, few generic Taiwan resistors, few Roedenstein resistors and the WIMA MKP combine with generic capacitors. The power supply capacitors are using the standard Panasonic. The input capacitors is using the Elna Silmic which I am really think this is the best capacitor for signal.

 

The amplifier and the power supply section are separate by aluminum heat-sink to minimize the noise from power supply section. As you can see the big dual capacitors are the oversized value required from the First Watt B1 Buffer circuit. They looks amazing in this amplifier casing.

Besides the toroidal transformer, the regulator power supply for the B1 buffer is using the LM317 adjustable regulator. It set to 18 volt as required by the First Watt B1 circuit.

At the first time, I assume this combination will generate little bit hum noise to the speakers when the amplifier in on idle. But in fact it is not. The amplifier is very silent, dead quiet I can say but once the music play, this combination makes the music play wonderful. I never thought I will get such this great result by only combining those 2 circuit.

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