Tube Amplifiers

Lyrita Audio

Horn Speakers About

The 2A3 Amp

Of all the DHTs (directly heated triodes), the 2A3 tube sits at the pinnacle. Introduced in the 1930s, the 2A3 has continued unchanged to this day. Some new production tubes are available, but most manufacturers continue to use new old stock. RCA was a prolific maker of this tube.

Tubes, especially directly heated triodes, have the lowest distortion signature of any amplifying device. Used in simple circuits, the 2A3 tube gives great clarity in music. Its portrayal of musical tone, texture, and harmonics is superb. In a well designed amp, the 2A3 brings music alive.

Lyrita‘s 2A3 amps are single-ended designs, as originally intended for this tube. SET- single ended triode. The circuits are simple, and use transformers extensively. Amp configurations can be customized for the user.

 

Simple 2A3 SET integrated amp  -  three stage, capacitor coupled, small chassis.

  Tubes - 6N1P, 6N6P, 2A3,  5C4S.     Power output - 3 watts/channel.      

 

2A3 SET integrated amp  -  three stage, capacitor and interstage transformer coupled.

  Tubes - 6N1P, 6N6P, 2A3, 5C4S.     Power  output - 3 watts/channel.

 

2A3 SET power amp  -  two stage, interstage transformer coupled.

  Tubes - 6E5P, 2A3, 5C4S.     Power output - 3 watts/channel.

 

All DHT 2A3 SET power amp  -  two DHT stages, interstage transformer coupled.

  Tubes - 45, 2A3, 5C4S.       Power output - 3 watts/channel.

The GM70 Amp

To provide a substantial increase in power output, and maintain the signature of the single-ended tube amp, the GM70 tube is ideal. Its properties are very similar to the renowned 845 tube - though the construction, pin layout, and heater requirements are different. The GM70 is a more robust and reliable tube.

Amp configurations can be customized.

 

GM70 SET integrated amp -  three stage, capacitor and interstage transformer coupled.  

 Tubes -  6N1P, 6E5P, GM70, 5C4S.    Power output -  20 watts/channel.

 

GM70 SET power amp -  two stage, interstage transformer coupled.

  Tubes - 6E5P, GM70, 5C4S.     Power output - 20 watts/channel.

 

A variation is the power monoblocks, with the GM70 tube operating at very high voltages. This is the ideal operating point for the tube, and it shines in delivering power and an extended response.

 

GM70 SET Mono power amp -  two stage, interstage transformer coupled.

  Tubes - 6E5P, GM70, 6C5S.     Power output -  35 watts/channel.

 

All DHT GM70 SET power amp -  two DHT stages, interstage transformer coupled.

  Tubes -  2A3, GM70, 6CM3, 6C5S.      Power output  -  35 watts/channel.

 

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Tube  Preamplifiers

DHT Line preamp

This line level preamp uses the Russian 4P1L, as a directly heated triode, in a very simple design. Filament bias is used, which aids in simplicity and stability. An audio transformer serves as a load to the tube, as well as isolates the output. This also controls microphonics in the tube. Volume control is on the output.

The sound is rich in tone, with excellent dynamics. A great start to the amplification chain.

 Tubes                      4P1L, 6C5S

 Gain                        12 dB

 Output Impedance    5000 ohms

 

 

Tubes -  4P1L, 6C5S.

Phono preamp

Tubes handle low level signals beautifully, with unmatched linearity. They are ideal for the minute signals from the phono cartridge, to amplify and equalize to RIAA specifications.

A new circuit design uses the high transconductance, high gain, dual tube, the Russian 6F12P. This tube brings great clarity in music, with excellent micro and macro dynamics.

The active circuit has enough gain for MM (moving magnet) and high output MC (moving coil) cartridges.

For low output MC cartridges, a step-up transformer is required, ahead of the active circuit. Consider this as part of the cost of a low output MC. Lyrita recommends step-up transformers from CineMag.

Our environment is becoming more noisy electrically, with high levels of RFI (radio frequency interference). The high gain tubes used in phono circuits are very susceptible to RFI pickup. The only way to prevent this is to provide shielding to the entire circuit and tubes. So, the chassis becomes a steel black box.

 Tubes                      6F12P, 5C4M

 Gain  MM                54 dB

 Gain  MC                 74 dB  with CineMag 1:10 step-up

 Output Impedance    3000 ohms