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Glen Wagenknecht
Financial Interests: click here
Sources: Audio Space CDP 8A CD Player
Luxman Brid CD Player modified by Audio Upgrades into a tube-less, zero oversampling machine with volume control
Preamplifier: Audio Space Reference 2S
Amplifier:Bel Canto 200.4
AV Receiver: Pioneer Elite SC-25
Main Speakers: Apogee Duetta Signature, Paradigm Servo 15 subwoofer
AudioSpace AS-3/5A
Stands: Charisma Audio Function Stands   Target
AV Speakers: JohnBlue M3s
AV Subwoofer: Paradigm PW-2200
Cables: Audio Art SE cable loom, JPS Labs Ultraconductor 2 speaker cables, Signal Cable Silver Reference interconnects and speaker cables, digital optical and coax cable.
Resonance Control: Solid Tech, EquaRack Footers, Weizhi Precision Gold Glory footers, Boston Audio TuneBlock2 footers, Superspikes, and Black Diamond
Powerline conditioning: Noise Destroyer power filtration
Accessories: TrueHarmonix Black Magic CD Mat
Main Room size: 12' x 17'
Home Theatre: 10.5’ x 16.5’
Review Component Retail: $4.995 preamp, $3.200 amp (silver version adds $200)

. It’s hard to believe that a man like Henry Ho can consistently find himself a small lightning rod of controversy but the introduction of his original H2O ICEpower amplifier put him at the center of a debate. In the light of 2011 it’s hard to fathom the attitudes that greeted the generation of high-end digital amplifiers which emerged in the early 2000s. Some saw them as a new alternative already matured and challenging the top ranks of traditional competition. Others used less flattering terms seemingly lifted straight from the vocabulary that greeted the introduction of transistor designs in the early 1970s. Henry Ho along with several other designers found himself in the vortex of this teapot tempest surrounded by equal parts accolade and derision. The introduction of his new Fire preamp stands poised to do the same.

The H2O amp was a departure from the massive traditional class A beasts that were the staple of Mr. Ho‘s earlier audio enterprise. Yet the potential and availability of the new so-called ‘digital’ modules piqued his engineering curiosity and he applied his existing knowledge of proven approaches to the new technology. As potential evolved into realized product, the H2O and its subsequent siblings were born. One of their key prerequisites was to drive Henry’s reference speakers, the infamous 1Ω Apogee Scintilla. Few can match its unenviable reputation for testing the stability of amplifiers. The combination of ultra-low impedance coupled with an insatiable desire for current and high power have driven many an amplifier to destruction. A daunting arbiter for any amplifier, the H2O is one of the few that meets the challenge with musical gusto.

The H2O S250 Signature is the latest version of an already successful platform and represents Mr. Ho’s desire to push the potential of the design further. To that end the changes are evolutionary. The new stereo amplifier retains most of its basic non-signature specifications, the 250/500wpc 8/4Ω rating and roughly 62lbs weight. The Signature version moves from a single large toroidal transformer to twin stacked 800VA units along with pure copper foil wiring in the power supply, Schottky rectifiers, an improved AC filter and top-line Mundorf silver/gold bypass capacitors which Mr. Ho describes as "murderously expensive".

The Fire preamplifier seems to be as radical a departure from traditional designs as was the earlier decision to move from class A to D and is likely to raise a few eyebrows. No svelte slim sleek modern design this. Henry Ho’s preamp is a big two-chassis Mosfet affair that emphasizes the amplifier in the pre. The 25lb head unit has the girth and height of a full-size amplifier complete with massive heat sinks on either side which aren’t for cosmetic purposes. This pre earns its name of ‘Fire’. Where the S250 runs efficient and cool to the touch, the Fire runs hot enough to necessitate those long rows of finely finned friends. The massive outboard power supply at another 25lbs is aptly named Firepower and only somewhat smaller. It contains a pair of amplifier-sized toroids and tethers to the main chassis via two umbilical power cords with locking connectors.

While there are several examples of promising Fet-based preamps, none to my knowledge have taken this upwardly thermal approach. Since the preamplifier was unusual it begged several questions and also presented me the opportunity to ask about the shift from class A amplifiers to D-class circuits.

Q. The Fire runs unusually hot for a preamplifier. Isn’t the approach here drastic overkill considering the fact that we’re only dealing with low-level signals?

A. Understood. The preamp is for low signal levels and most of the time supplies the power amp with a few milliamps at most. But the Fire was designed for ultra linearity. To do that the transistors require lots of biasing current since the Fire is a Mosfet design which requires significant bias current to achieve linearity. In fact Mosfets are sometimes criticized for sounding nasal, misty and veiled, lacking resolution and clarity on top. I happen to completely agree. Most if not all Mosfet amplifiers sound that way. To solve that, Mosfets need serious bias current. The Fire draws about 100 watts total and runs 0.5 amps of DC current through its output stage which I think is unheard of in a preamplifier design. Overkill? It still sounds beautiful with 1/10th its bias current and a power supply 1/10th the size but why settle for second best? For this reason the power supply consists of twin 250VA toroidal power transformers with 156.000uF of filter capacitance decoupled by 396.000uF post regulation. The whole design is completely dual mono.

Q. In the course of listening I found that the preamplifier pulled up a lot of low-level information. Low-wattage tube amps do that with soft clipping and compression. Yet you appear to be able to muster good dynamics so I'm wondering how? Is this something intrinsic to the transistor you use or is it something you've done within the circuit?