Gainclone Amplifier build

It all started in 1999.

47 Laboratory (Junji Kimura) introduced the 4706 Gaincard amplifier, which produced 25 Watts per channel from a single IC chip amplifier per channel.

The special features of this amplifier design were:

  • A ‘high-end’ dual-mono amplifier designed around a single power IC (per channel)
  • The world’s smallest number of parts in an amplifier (9 per channel)
  • The world’s shortest signal path length (32mm including parts lengths)
  • The world’s shortest negative feedback loop (9mm)
  • Smallest possible Power Supply filter capacitance (1,000uF) combined with a high capacity power transformer
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Vacuum tube Headphone Amp-DAC

The Sennheiser HD 650 is a great headphone with a little bit of sonic ‘magic’ appeal. The attractively priced MassDrop HD 6XX version is a special bargain.

A popular and nice match for the Sennheiser HD 650 / HD 6XX is a vacuum tube headphone amplifier.

The project here was built by Jeremy Young. It was inspired by the Bottlehead OTL headphone amp, but circuit ‘operating points’ were determined to suit a locally made power transformer.

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Consider Connectors

“God is in the detail” – Ludwig Mies van der Rohe (et al)

Sometimes it’s necessary to re-examine the little things, the forgotten details.  Try to dig out the last 10% improvement.

Consider amplifier and loudspeaker connectors.

We know that music signals are alternating current, AC not DC – swinging positive/negative.  We know also that “current in a conductor resides at the surface at high frequency” (Prof. Malcolm Hawksford, HFNRR Aug 1985): Continue reading

Amplifiers on the bench

After purchasing a (Tonghui) dB-Millivolt meter, I am able to more easily (and more accurately) undertake frequency response measurements of my Preamp and Power amp.

This enables me to directly read relative dB signal voltage output from my amplifier (or preamp) without laborious 20Log Vout/Vin calculations. (Thanks to advice from my pal Clarry.)

I will check out my recently built WOT Preamp and my usual 2A3 Push-pull amplifier. Continue reading