The Preamplifier
Through the extensive research and development, we can offer one of the ultimate expressions preamplification.
Like most Treehaus Audio products, a proper power supply is critical. The preamplifier has a separate power supply to keep noise transmission to an absolute minimum. The power supply utilizes a variety of power transformers within it for the various circuits of the preamplifier. A pair of 6CJ3 provides high-speed DC voltage tube rectification to the audio circuit.
Volume attenuation is performed through a TVC (Transformer Volume Control). In this configuration, a pair of Finemet transformers connected to a 24-position switch converts between voltage and amperage. This method does not dispose of any sonic information as it attenuates the audio signal to the preferred listening level. Music does not lose any detail or energy, regardless of listening level.
The properly attenuated signal is then sent to an amplification stage using the 4P1L directly-heated vacuum tube in triode configuration. The 4P1L has a low plate resistance is ideally suited to make a low output impedance preamp. The sound is clear and clean with the pleasing predominant 2nd harmonic. The tube is run in filament bias mode, with the filament supply provided by a Coleman regulator. This has the advantage of using a very low value resistor to bias the tube and therefore there is no need to decouple it with a capacitor. The entire gain stage is completely free of coupling or decoupling capacitors, making the sound uncolored by capacitors. Custom made output transformers using Finemet cores complete the signal path.
Special care has also been taken to the usability of the preamp as the control center of system. There are standby and power switches so operation is easy. (We use a special 12VDC circuit for the power switch so that no AC current is in the main preamplifier unit). We also utilize a remote control to operate the attenuator switch so volume adjustment from the listening position is effortless.
Special care has also been taken to the usability of the preamp as the control center of system. There are standby and power switches so operation is easy. (We use a special 12V circuit for the power switch so that no AC current is in the main preamplifier unit). We also utilize a remote control to operate the attenuator switch so volume adjustment from the listening position is effortless.
Cardas connectors are used for the RCA inputs and outputs. Elma rotary switches are used for input selection and volume attenuation via the TVR. MIL-spec Amphenol connectors supply power to the preamplifier via an umbilical cord. A hardwood veneer case over Baltic Birch multi-ply core is used for encasing the boxes, with 5mm oxidized aluminum plates and patinaed brass knobs complete the aesthetic.
The Treehaus Preamplifier is $17,000 including vintage/ NOS tubes where appropriate.
A word about Finemet
You may notice we pride ourselves on using Finemet-core transformers in the audio signal path. We have found these transformers to be some of the best available after extensive benchmarking of both vintage and modern audio transformers.
Finemet is Nanocrystalline soft magnetic metal which is special amorphous metal produced by Hitachi Metals, LTD. Its phase characteristics is far better than conventional core material such as Ni and Co-based amorphous metal. It both satisfies both high saturation magnetic flux density and high permeability. The high saturation magnetic flux density is comparable to Fe-based amorphous metal. High permeability comparable to Co-based amorphous metal. Finemet has 1/5th the core loss of Fe-based amorphous metal and approximately the same core loss as Co-based amorphous metal. The low magnetostriction is less affected by mechanical stress, and therefore there is very low audio noise emission. The high frequency characteristics are excellent due to the high permeability and low core loss over wide frequency range, which is equivalent to Co-based amorphous metal.
Finemet transformers have a very good phase response; they are VERY transparent. These transformers are designed and manufactured by Mr. Suzuki, General Industry, in Saitama Japan. They supply transformers for many well-known Japanese audio companies. The winding material and techniques are closely guarded trade secrets by the manufacturer. We offer them both as nude transformers (with an Urushi lacquer applied) or in a metal case, depending on the aesthetic preference of the customer.