Kenwood Model Nine (1960–1962)
Four KT88s, no negative feedback, and a Peerless transformer doing the stabilizing work - this is Kenwood before it was Kenwood.
Overview
The Kenwood Model Nine is a stereo vacuum tube power amplifier that Kenwood built from 1960 to 1962. At the time, Kenwood - known as Trio Electronics in Japan, where this amp was sold as the Trio W-9B - was largely manufacturing consumer electronics for other companies. The Model Nine was a significant design for them, a statement piece that showed what they could do when building under their own name. It originally sold for $250, which in 1960 placed it in serious-hobbyist territory. It was offered as part of the 1960 "Model System," bundled with the Kenwood Model Eight vacuum tube preamplifier and the Model Eleven tuner.
This is a power amplifier, plain and simple. No phono preamplifier, no tone controls, just an input board and an output stage. The tube complement is two 12AX7s up front, three 12AU7s as drivers, and four KT88s doing the heavy lifting in a push-pull beam power tetrode configuration. Four KT88s, wired directly to the output tube sockets, with each screen wired separately to the plate of its corresponding tube. You don't see a layout like that in most consumer gear of the period.
Owners describe it as fast, precise, and detailed, with an uncolored sound that lets the source material through. The bass is tight and controlled, and the highs are smooth and extended. The one recurring criticism is the deep bass. A reviewer notes that the only real weakness is the deep bass frequencies, which they attribute to the no-negative-feedback design.
Key Features
No Negative Feedback — The Peerless S-2650 Output Transformers
The big decision in the Model Nine's design is the complete absence of negative feedback. Classic Audio is explicit about this: "This amplifier has no negative feedback." Instead, the stabilization duty falls to the Peerless S-2650 output transformers, which stabilize the speaker-to-amplifier interface. Most amplifiers of the era leaned on feedback to flatten response and lower distortion. The Model Nine leans on iron. Owners describe the sound as uncolored and detailed, with that noted softness in the deepest bass, which is the direct consequence of the no-feedback topology.
Four KT88 Output Tubes, Push-Pull
The output stage is built around four KT88 beam power tetrodes in a push-pull arrangement. That's a lot of tube for 1960. The wiring runs directly to the output tube sockets, and each KT88's screen is wired separately to the plate of the corresponding output tube. Screen resistors protect each KT88 individually, and an alternate pair of power supply leads is provided so the output stage can be powered separately from the front end. That separate connection is there to support bi-amplified systems, which the Model Nine was explicitly designed for. Each channel has its own input and power supply connections, so you can run the amp as two independent monoblocks.
PC-408 Input Board
The front end is contained on a single input board, designated PC-408, which houses the input amplifier circuitry. It's a minimalist, modular approach: one board for the sensitive stuff, with the output stage handled by the tube sockets and transformers. Inputs are standard RCA jacks, and outputs are terminal strips. There's a 16-ohm speaker output on tap. Input sensitivity is 1 volt, which makes it an easy partner for most preamps of the period.
Historical Context
The Model Nine was manufactured from 1960 to 1962, and it was sold as part of the 1960 "Model System" alongside the Kenwood Model Eight vacuum tube preamplifier and the Model Eleven tuner. In Japan, it was known as the Trio W-9B. It came when Kenwood was still largely manufacturing consumer electronics for other companies. Classic Audio puts it bluntly: "It's likely the finest amplifier ever produced by Kenwood."
One owner notes that "30 watts is plentiful." The output figures vary by source and measurement condition. hifi-wire lists 40 watts per channel RMS at 8 ohms, Classic Audio lists 60 watts per channel into 4 ohms, and a Reverb listing cites 30 watts. Frequency response is rated at 10Hz to 100kHz (+0 -3dB), with signal-to-noise ratio at 74dB and harmonic distortion at 0.5%. Power consumption is 180 watts.
Collectibility & Market
If you want a Model Nine, bring patience and money. The amp is "very scarce in the US market," and forum commentary describes it as hard to find and expensive when you do. A Reverb listing shows one in "Very Good" condition at $2,500, and speculation values range from $1,500 to $4,000, though actual sales are rare enough that those numbers are more aspirational than empirical. Collectors are blunt about it: "These are quite rare and collectible."
The scarcity comes from both the short production run and the design's reputation. This isn't a mass-market receiver that survived in quantity. It's a specialized power amp from a company that was still finding its identity. The KT88 output tubes and Peerless transformers give it real engineering pedigree. The deep bass limitation is real, and anyone considering one should factor it into their speaker choice.
Information on common failures, maintenance procedures, and spare parts availability is thin. The screen resistors on each KT88 and the alternate power supply leads suggest Kenwood was thinking about reliability, but if you're buying one today, budget for a full recap and a careful look at the tube sockets. The Peerless transformers are the heart of the design, and they're not easy to replace.
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