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
Continue reading

Keith Monks Record Cleaning Machine

The Keith Monks Record Cleaning Machine was introduced in 1969 and is still unique in the method used to vacuum-dry the cleaning fluid from the vinyl record.

The KMAL (Keith Monks Audio Ltd) Record Cleaning Machine was originally developed from a ‘Record Doctor’ concept devised by Percy Wilson in England and presented to the Audio Engineering Society (AES) in 1965.

In 1969, Keith Monks was successful in securing orders from the BBC for the first KMAL Record Cleaning Machines to be manufactured.

Continue reading

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.

Continue reading

LONDON DECCA cartridge with Decapod

Replacing the standard Decca 2-piece plastic mount with a ‘Decapod’ (solid aluminium) mount, is essential in my opinion and I recommend it.

The Decapod ‘mounting block’ is obviously a much more solid connection between the cartridge and the tonearm, than the original Decca design

And, I can advise that the Decapod will transform the sound of your ‘standard’ London Decca or Decca cartridge.

Continue reading

Jimmie Dale Gilmore + Butch Hancock – Auckland, NZ

American country singer and song-writer, Jimmie Dale Gilmore, played in NZ in 2015 but this time (pre-pandemic on 1 March 2020), he brought Butch Hancock, fellow-member of legendary The Flatlanders trio.

As I was unlikely to visit USA again in the near future, I didn’t want to miss an opportunity to see Butch Hancock, another respected singer and song-writer.

Top class, these guys from West Texas are the real deal.

One of the most enjoyable Americana-country concerts I’ve attended. Outstanding.

Continue reading

Fidelity Research FR-64 tonearm

This vintage Japanese tonearm still enjoys a certain ‘cult’ status.

Fidelity Research Co. was founded by Isamu Ikeda in 1964 and the FR-64 tonearm was introduced in 1978. Fidelity Research closed down c.1984.

(A new company, Ikeda Sound Labs, currently again offers new cartridge & tonearm products.)

The detailing and machine-finishing is visually uncomplicated. After 40 years, it still looks elegant and the material is durable and un-tarnished.

Continue reading

WOT tube line-stage – update

Some of the appealing things about Output Transformer coupling are :

  • In a line-preamp, only 1 tube stage is required – simplicity / transparency.
  • No second stage ‘cathode-follower’ output is required.
  • No DC-blocking, output coupling capacitor is required – less colouration.
  • Much better circuit ‘efficiency’ – much lower energy loss in the tube plate circuit (compared with resistor plate loading).
  • Thus, a smaller, more efficient PSU is possible.

(See previous post – WOT tube line-stage redux.)

Continue reading

Concertgebouw – Amsterdam

My first visit to the Royal Concertgebouw concert hall in Amsterdam on 21 May 2019.

The acclaimed pianist Yuja Wang performed with the City of Birmingham Symphony Orchestra and Lithuanian conductor Mirga Gražinytė-Tyla.

The programme was:

  • M. Weinberg – Rhapsody on Moldavian Themes, op. 47/1
  • Prokofjev – Piano Concerto No. 5, op. 55
  • Prokofjev – Vivo from Piano Concerto No. 5, op. 55 (encore)
  • Stravinsky – Firebird

Continue reading