In Barn for Review: Treehaus Audiolab The Preamplifer & 300B-2 SET Amplifier

I’ve been up the Treehaus Audiolab path before with my review of their ‘Phantom of Luxury’ Field Coil Loudspeakers about which I said:

“…the Treehaus Phantom’s do have a phantom-like quality in that they create a compellingly tactile presence with the beating heart of music feeling rich and harmonically right with delicate beauty and/or guts and heart-pounding glory morphing with the music in play. And there’s no denying the Phantom’s stunning unusual looks which I find appealing—I appreciate the art and craft involved—and they essentially act as an initial litmus test for potential buyers to a greater degree than a ‘traditional’ box speaker.”

As you can see, the Treehaus Preamplifer and 300B-2 SET offer similarly stunning looks, to my eyes, that pay tribute to our rich hifi history. And that tribute digs deep inside as well.

The Preamplifier is a line-level preamp, Treehaus also offers their ‘The LCR’ Phono Preamplifier for vinyl people, housed in two chassis separating the power supply from its directly-heated triode-based pre-amplification. The review pre came with the optional remote volume control.

From Treehaus:

Volume control is performed through a TVC (Transformer Volume Control). A pair of Finemet transformers and a multi-position rotary switch simply alter the input signal’s ratio of voltage to 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 the 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 preamplifier. 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, yielding a sound uncolored. Custom made output transformers using Finemet cores complete the signal path. The Treehaus Preamplifier essentially is a SET amplifier in design philosophy.

The Treehaus Preamplifier comes with 3 to 5 Cardas RCA Single-Ended inputs and two pair of Cardas RCA single-ended outputs. An included umbilical cable ties pre to power. There are a pair Gain switches to adjust the output for 6.5dB or 13dB of gain to help match your system’s needs.

photo credit: Treehaus Audiolab—the Preamplifer in the ‘A/Machines’ style. The review set is finished in the Kinsuido style.

I recommend a visit to the Treehaus website where you can learn a lot more about the design and philosophy behind their products as well as the different finish options for the Preamplifier and 300B-2. Here’s a taste from the About page:

The search led us deep into some esoteric points in time in the development and refinement of sound reproduction. In Germany, the 1930s and 1940s brough us the work of Telefunken, Siemens and Klangfilm. The 1950s in the United States was the era of Western Electric. Lesser known, in the 1980s and 1990s, while most of the world had moved on from the magic of vacuum tubes for the simplicity and economy of transistors, a dedicated group of enthusiasts in Japan kept the glass warm and refined the art of tube amplification (and from which the term “Audio Mania” derives). After years of research, buying a variety of equipment from these places and time periods, the path to best sound would be to unify the elements of the audio moments in a modern execution. Treehaus Audiolab products are the fruit of this obsession.

Treehaus makes three 300B-based amplifiers—the 300B-1, 300B-2, and 300B-4. Can you guess what the numbers mean? Yup, number of chassis. The Treehaus 300B-2 is another two chassis design with the power supply residing in its own matching home. The four potentiometers and meters you see up top are for adjusting the Coleman Filament Regulators (for ‘heating Directly-Heated Electron Tubes’), a process that sets the tube filament within +/- 3% of the desired voltage to ensure good sound and long tube life.

From Treehaus:

The 300B-2 Amplifier separates the signal section and power supply section into two enclosures. It 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 300B-2 offers a pair of Cardas RCA single-ended inputs, one pair of Cardas speaker binding post, and an input for included umbilical cable to tie to the power part.

the 300B-2 comes with NOS tubes and a pair of Stradi 300Bs from Korea. Western Electric 300Bs are also available.

The 300B-2 puts out about 6 Watts of power which is more than enough to drive the review pair of DeVore O/Bronze to Barn-rattling heights and I say this with confidence because I’ve already heard it happen.

If you’ve been counting along, the Treehaus 300B-2 is the third 300B-based amp in Barn, joining the Audio Hungary Qualiton 300B Integrated Amplifier and the Audio Note Meishu Phono 300B Konzertmeister Integrated Amplifier. If you’re hoping for a shootout, I recommend watching Wyatt Earp as my designs are to suss out how each of these pre and amplifiers make music sound an feel.

Treehaus Audiolab Preamplifier: $24,000
Treehaus Audiolab 300B-2 SET Amplifier: $30,000
Company Website: Treehaus Audiolab

The Preamplifier Specifications

Two enclosure design (Signal section and Power supply section).
Finemet TVC (transformer volume control) with stepped attenuation. Remote option available.
Toroid power transformer with CLCLC power supply and Finemet choke in final stage.
6CJ3 tube rectification.
4P1L DHP vacuum tube operating with filament bias utilizing Coleman Regulators.
edenSound Terrastone and IsoDamp vibration mitigation.
Finemet output transformer with high/low gain switch.
Line Inputs: 3 to 5 RCA Single-Ended.
Line Outputs: 2
Input impedance: Min 40K.
Maximum output voltage: 4Vrms @ 2Vrms input (low gain), 8Vrms @2Vrms input (high gain).
THD: lower than 0.05% at 4Vrms output (low gain), lower than 0.05% at 8Vrms output (high gain).
Frequency response: 20-20Khz +/- -0.2dB.
S/N ratio: ≥ 90db.
Output gain: 6.5dB/ 13dB (user selectable switch)