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Introduction

As you might have noticed, my philosophy in audio design is usually based on the statement "the simpler the better". Therefore, the preamplifiers line stage could just be a passive preamp which goes between your CD player and power amplifier!

Unfortunately, the world is not that simple - a "passive preamp" cannot drive long cables! A 10 kohm passive volume control, for example, has a far too high source impedance for cables longer than half a meter, whereas 10 to 20 cm would be ideal! Having a long cable, you either put the volume control into the power amplifier or you definitely need a line stage capable of driving large capacitance.

On the one hand designing an excellent line stage may be a challenge, on the other hand it is easier to design a line stage than a MC phono stage!

At 50 Hz and below, the MC circuit must amplify the input by approx. 1000 times. (A line stage just 5 to 10 times). Also the input noise of the phono stage must be extremely small in comparison to the typical half a millivolt output of MC cartridges. According to this, for MC phono stages there are three main requirements: You need very high gain, very low noise and finally very precise frequency equalisation (RIAA).

Altogether, there are a lot requirements to rack one's brains!

Design Considerations

Amplifiers are much more variable in sound than often suspected. Knowing the sound of the power amplifier No. 2 Megalith, it has been obvious to use an identical topology for the line stage. Moreover, this circuit is perfectly suited for driving long cables and low impedances (I use about 6 meters without any problem).

Trilith - Line Amplifier No.3

Along with the effort of designing the Trilith Pre-Amplifier, I considered another topology.


Details for the Trilith MC/RIAA Amplifier Stage

- Complete Schematic Diagram 1a  (PDF, 18 KB)
- Printed Circuit Board 1a  (PDF, 260 KB)
- Bill of Materials 1a  (PDF, 12 KB)
- FFT Harmonic Spectra and RIAA Equalisation  (HTML, 200 KB)

Details for the Trilith Line Amplifier Stage

- Complete Schematic Diagram 1a  (PDF, 19 KB)
- Printed Circuit Board 1a  (PDF, 260 KB)
- Bill of Materials 1a  (PDF, 12 KB)
- FFT Harmonic Spectra  (HTML, 80 KB)

Details for the Trilith Battery Supply Unit PCB

- Schematic Diagram 1a  (PDF, 11 KB)
- Printed Circuit Board 1a  (PDF, 128 KB)
- Bill of Materials 1a  (PDF, 15 KB, updated)

Details for the Complete Trilith Pre-Amplifer

- Pre-Amplifier Block Diagram Version 1a  (PDF, 13 KB)
- Pre-Amplifier Block Diagram Version 2a  (PDF, 11 KB)

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