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Alright, fast forward to 2005. George Kaye and his business partner Gage Rommel set up a company called Moscode Corp. After twenty years, the time had come to revive the name and the tube/Mosfet hybrid concept. These 20 years hadn't just gone idly by. George had used them to play plenty of bass and to refine the original design. In reworking it, the strengths of the circuit have been left untouched. It is still a Mosfet power stage driven by tubes and it still sounds like how Gizmo originally voiced it. Today's incarnation simply uses modern fabrication techniques, current quality parts and then adds an important extra.

In the spiritual heritage of Harvey Rosenberg, the Moscode 401HR power amplifier is ultra modifiable. Harvey -- like any real man -- simply could leave no toy untouched. This obsession earned him his nickname after all. Whether it was a Harley-Davidson motorcycle, a Winchester rifle, a hand bow or even his cigar, everything had to be adjusted, tweaked or adorned with a mere piece of Ductape, the ultimate tweaker's weapon. The 401HR as a true tribute to Gizmo would make him smile all over now.

When we start at the front of the amplifier -- it's available in semi black gloss or clear-anodized aluminum -- there's a flippant faceplate that can be pulled down. By doing so, you gain direct access to the two pairs of driver tubes visible behind the closed glass panel whose etched Moscode logo illuminates in operation and flashes during preheating.

The two pairs of double triodes are swappable and the main attraction of this amp. Standard trim are Sovtek 6H30Pis and Electro Harmonix 6FQ7s. The first pair -- the outer wing men so to speak -- is predominantly responsible for the overall sound and tone of the amp as it handles voltage gain. The second inner team is a follower pair. Its sonic influences are not as large. Since the chosen valves are very popular, a multitude of makes, production years and models are readily available on the market. George Kaye chose the stock glass to produce solid bass, attractive female vocals and a good soundstage. Rolling tubes as we shall see later is child's play because George incorporated a special circuit that enables hot swapping on the fly.

At the back of the amplifier is as little as possible - an IEC power inlet and accompanying fuse, a pair of RCA inputs and a standard remote power trigger. Above and in the middle sits the front panel illumination control that adjusts the intensity of the LEDs behind the faceplate.

George Kaye opted for the special 5-way Edison Price Music binding posts, which use pure OFC copper without any plating and are direct-coupled to the output stage circuit board. These designer posts accept all manner of spade lugs, banana plugs or bare wire and are easy to fasten by hand. They need a little extra care now and then however to remove oxidation [and should not be over torqued to prevent stripping - the pure copper is softer than conventional binding posts - Ed.].

The 401HR was designed with all kinds of customers in mind, so it adds a toggle in the back that selects between stereo, vertical bi-amp and mute operation. Vertical bi-amping runs two 401HR amplifiers whereby each amplifier gets dedicated to one loudspeaker. One channel drives the woofer, the other the tweeter (or tweeter and midrange). The bi-amp switch thus routes a twin mono signal from a single input to both channels.

The manual is very clear on how to set up the 401HR. Special attention should be paid to the mains connection. The design of the amp grounds the chassis to AC ground. This could cause hum depending on the grounding of the connected equipment. We had to run a power cord from an ungrounded wall receptacle to the Moscode amp to eliminate 50-cycle hum.

But first things first. We connected the 401HR to the pre-out of our Audio Note Meishu and installed the supplied tubes. From the Edison Price binding posts we ran Crystal Cable to our Avantgarde Duo Omegas. After switching on the rest of the machinery, the large button at the front of the amp brought things to life. The LEDs were blinking during the initial warm-up phase and after about a minute, a soft relay click notified us that all passengers had boarded and we were ready for lift-off. The four tubes glowed cozily and the blue logo in the middle held steady.

Rewiring the AC connection completely killed the ground loop after which the amp was as quiet as a church mouse even into our 107dB speakers. With 200wpc on tap, that was hardly a bad start. It took about 100 hours to loosen up the amp completely. At that time the first of a series of review loudspeakers arrived in our Rotterdam pad. With George's and Gage's consent, we decided to use the 401HR on all of 'em. Over the next few months, we ran Tannoy's Glenair, Mobile Fidelity's OML-2, Quad's ESL 2905, Von Schweikert's VR5-SE, Haliaetus' Firebird, Final's 1000i and our resident horns. To top things off, we even ran a Velodyne DD12 from the Moscode hi-level output. This group of loudspeakers represented goodly variety, ranging from dual-concentric and conventional dynamic drivers to two types of electrostatic planar designs. Sensitivities ranged from 86dB to 107dB. To mix things up further, preamps like the Lamm LL2 and KR Audio Model 150 stopped over to insert into the signal chain as well.

To get an idea of what the Gizmological factor in the 401HR entailed, we set out on a hunt for alternative tubes. Who else to query but Peter van Willenswaard at his Audio Magic company? Peter is a walking tube encyclopedia with a substantial stock of NOS tubes. On our request, Peter assembled a short list of tubes we might like to try. We ordered them all just for Harvey's sake. A few days later and we had our little stack of Svetlana 6N1P, Tesla Prague E88CC SQ (for medium mu tubes) and Convair 5814, GE 5814, RCA 6FQ7 and Thermionic 12BH7 for low mu variants. Together with the stock 6H30Pi and 6FQ7 low
moosters, this made for quite a few possible permutations. All of these bottles could be seated in either position except for the 6H30Pis which tend to oscillate when used as a follower.