The Amplifier
Our signature amplifier utilizes a Directly Heated Triode (DHT) driver interstage transformer-coupled to another Directly Heated Triode acting as the power tube. This design is based on the work of the Japanese master-of-the-art Susumu Sakuma, with a deep reference to the earliest Western Electric designs. Sakuma recognized the symbiotic sonic relationship that forms when a DHT drives a similar DHT. The pleasing distortions of the second harmonic are enhanced while less desirable harmonics are minimized in this configuration. The architecture yields one of the purest expressions of what vacuum tubes can offer the listener.
We chose to use the 10/ 801A series of tubes for the driver: This tube is extremely clean sounding, offers a strong amplification factor within the DHT family, and with quite a few varieties, allows for some unique tube-rolling opportunity. The power tube is the venerable 300B. The 300B offers the power and headroom needed for dynamic music passages on high efficiency speakers. The 300B circuit we use has been tuned to eliminate some of the syrupy sound this tube can express on some of the more classic circuits; it has more of the character of a 71A/ 45/ VT-52, but with the energy only a larger-plate tube can provide.
Finemet transformers are used for the Treehaus Amplifier, made for us in Japan. A Finemet interstage couples our 10 to the 300B; no capacitors are in the signal path. A larger Finemet transformer performs impedance-matching output duty. Extensive benchmarking within our Lab showed these transformers have no equal. The sound is clean, pure, with no etch.
The separate power supply utilizes several power transformers within it for different circuits within the amplifier. A pair of 6CJ3 provides high-speed DC voltage tube rectification to the audio circuit. High quality filament power is essential for Directly Heated Triodes: as their name states, the tube heater is directly tied to the cathode of the tube. Unlike an indirectly heated tube, the heater is tied to the audio amplification circuit. We utilize separate AC/DC supplies for each tube, with a Coleman filament regulator to provide ideal power to the heater. The LED displays on the amplifier allow for setup and adjustment of this critical voltage application.
Cardas connectors are used for the RCA inputs and speaker outputs. Amtrans resistors are used in the capacitor-free signal path. MIL-spec Amphenol connectors supply power to the amplifier via an umbilical cord. A high-mass 5mm CNC milled oxidized aluminum plate secures all components, while the lower casing is made from either solid hardwood, or veneer over Baltic birch plywood.
The Treehaus Amplifier is $18,000 including Western Electric 300Bs, and 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.