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Teres (Mono)

TRANSFORMER COUPLED HYBRID POWER AMPLIFIER

Single-ended tube input stage loaded with a phase splitting transformer controlling 2 separate out of phase single-ended amplifiers for output. The tube handles all the voltage gain needed. It uses a new generation of our choke-rectified shunt-regulated power supply providing a noise-free operating point, clear tone and unbelievable dynamics.

The output stage’s power JFET cascodes form a bridge that when unbalanced by the input signal via the 2 transformer windings restores balance by adjusting their current conduction through the load. The 2 output stages actually enclose the load in their control loops and try to correct each-others errors reducing the distortion to insignificant amounts, leaving the “character” of the input stage untouched. Those provide no signal gain, they merely satisfy the load’s hunger for current.

To reduce the amount of heat generated the amplifier is biased so only the first few watts are in true class A. Music has a crest factor of 10 on average. This means that most of the time we listen at 1/10th of the peak levels. For most users this translates to under 5W. Peaks can reach over 100 watts during playback, but only for a few milliseconds. For those peaks the amplifier switches to class B using only one leg of the output stage capable to deliver up to 250W/8ohm and 350W/4ohm  Not sharing a common reference point apart from the load itself makes the second output stage correct for any error produced by the first one.

The result is an amplifier capable of extreme power while delivering exquisite smoothness and low-level resolution.

The driver stage is isolated by the interstage transformer and is not influenced in any way by the output stage maintaining tone, colour and resolution at all power levels and loads. Having the output stages floating around the load prompted for the use of a unique biasing technique powered by solar cells. This was the quietest galvanic isolated power we could come up with. Using opto-electrical conversion we control the bias by adjusting light intensity in the control circuit. Teres is an example of modern technology solving age-old problems allowing us to go a step beyond what was possible before. The physical appearance of Teres has the kind of understated elegance typical for Thrax.

The exquisite aluminum finish adds to the presentation of a solid block of metal.

Enjoy.

  • Long-life input vacuum tube
  • Custom phase splitting transformer
  • Silicon carbide rectifiers
  • Shunt-regulated power supply for the tube stage
  • Solar cell bias of output stage
  • Microprocessor-controlled operation
  • NO feedback
  • Special grade screened power transformer
  • JFET/MOSFET cascode output devices
  • Modular construction
  • Available in stereo and mono version
  • Transformer input on the XLR for true balanced operation
  • Solid machined aluminum chassis

TECHNICAL SPECIFICATIONS

Weight: 25kg
Dimensions: 340x450x230mm
Power: 450Wmax 115/230V 50/60Hz
Max. input level: 7V Rms
Output Power: 250W/8Ohm 350W/4Ohm
Gain: +16db
Input impedance: 47k Ohm
Output impedance: .35 Ohm
Signal to Noise: 112db
Frequency response: 20-20,000Hz +/- 1db