Kenwood 700M (1975–1976; some sources say 1977)
Kenwood's first big power amp - 170 watts a side, a 100 dB signal-to-noise claim, and a noise floor that owners still argue about five decades later.
Overview
One hundred and seventy watts per channel, minimum RMS, into 8 ohms, from 20 Hz to 20 kHz, with no more than 0.1% total harmonic distortion. That is the number Kenwood put in front of American buyers in 1975, and it is the number that has followed the 700M ever since — through the ads, through the spec sheets, and through every forum thread where somebody finally gets one on the bench and starts measuring. The 700M was the main power amplifier of Kenwood's 700 Series, a solid-state stereo power amp built in Japan and sold alongside the 700T frequency-synthesizing tuner and the 700C preamplifier-control. The trio was pitched as a system, and Kenwood's advertising treated it as one.
Collectors don't care about the wattage much - plenty of American iron from the same years claimed more. What matters is where the amp sat in Kenwood's own catalogue. German collector documentation describes it as the manufacturer's first large power amplifier, and as one of the highest-quality pieces Kenwood built. That is a strong claim for a company that made a lot of receivers, and it is why the 700M turns up in the same conversations as far more expensive separates. The same source draws a line from the 700 Series to the founding of Accuphase. Take that as the source's claim, not settled history.
Almost everything known about the 700M's performance traces back to Kenwood's own advertising copy, which ran in the American hi-fi press from early 1975 into mid-1976. No independent bench test of this amplifier is in the archive. The 170-watt figure, the 20 Hz - 20 kHz window, and the 0.1% distortion ceiling are manufacturer claims, repeated essentially unchanged across the campaign. They are not third-party measurements. Treat them as the design target, not the delivered result.
Key Features
170 Watts per Channel, Minimum RMS into 8 Ohms
The rating is a minimum-RMS full-bandwidth figure: 20 Hz to 20 kHz, both channels, 8 ohms, distortion capped at 0.1%. That is a more conservative way to state power than the "watts" numbers that dominated receiver advertising of the period, and Kenwood led with it. High Fidelity (February 1975, p.55) carried the campaign copy describing the 700M's output as "masterful," with the same 170-watt, 20 Hz - 20 kHz, 0.1% THD specification spelled out in the ad. The identical campaign, same figures, was still running in Audio (April 1976, p.37) more than a year later. Owners describe the amp as having plenty of power for low-efficiency speakers, the kind of load that makes lesser amplifiers audibly strain.
100 dB Signal-to-Noise Ratio and a 40 Damping Factor
On paper the 700M looks quiet and well-controlled: a 100 dB signal-to-noise ratio and a damping factor of 40. In practice, that is where the arguments start. An owner critique published alongside the HiFi Engine documentation is blunt. It says the 700M has a very high noise floor, a weak damping factor, and a weak slew rate, and the same owner rates the general specifications below those of the KA-7300, which they say sounds better with most speakers. That is one person's assessment, and it runs directly against the 100 dB claim on the spec sheet. Both can be true at once, since a 100 dB figure measured under lab conditions and a noise floor you can hear through efficient speakers don't rule each other out. Expect the real-world noise performance to be the point of contention, not the headline number.
1V Input Sensitivity
Input sensitivity is listed at 1V. That is the normal range for a power amplifier fed by a separate preamplifier, in this case the matching 700C. It is a plain, unremarkable figure. The 700M is a power amp, it expects a line-level signal, and it delivers 170 watts when it gets one.
Solid-State Construction with Full Service Documentation
The 700M is a solid-state stereo power amplifier, and unlike a lot of orphaned vintage gear, it is documented. A service manual and schematic exist, and a 12-page English instruction manual survives that includes connection diagrams and a block diagram. For anyone considering a restoration, that paperwork counts for more than any single specification, because a technician is not reverse-engineering the circuit from scratch. The amp also turns up regularly in "fully restored," "recapped," and "pro serviced" listings, which suggests the restoration path is well-trodden.
Historical Context
The 700 Series was a three-piece set: the 700T tuner, the 700C preamplifier-control, and the 700M main amplifier. Kenwood's advertising called the trio "incomparable" and framed the series as the company's state-of-the-art plateau. The campaign ran in the American press from early 1975 into mid-1976, and the 700M's production years are generally given as 1975-1976. At least one listing dates the amp to 1977, so the end of the run is not perfectly settled.
Documentation on the 700M is thin, and what survives is mostly Kenwood's own advertising rather than independent review coverage. The amp is well documented by a company that was proud of it, but it has no deep bench-test record behind it.
Collectibility & Value
The 700M has a real following, and prices reflect it. A Canuck Audio Mart listing for a 700M and 700C pair was asking CA$5,200 as of April 2025. Individual amplifiers show up on Audiogon described as fully restored, refurbished within the previous two years, with switches cleaned and bench tested. Reverb listings describe 700M and 700C sets in great working and cosmetic condition, and another 700M as "pro serviced." An older eBay listing for a tested 700M asked $2,200. A Russian-language listing describes a unit as technically functional and stable, with wear consistent with age.
The owner critique points to the buying advice: the 700M is a high-quality build with a noise floor that some listeners find objectionable. Audition before committing to a premium asking price, and weight the value toward documented restoration rather than cosmetics. There is no consolidated failure pattern in the record beyond the usual recap-and-clean work that restored examples have already had done. The 700M is not a bargain-bin amplifier, and the market does not price it like one.
eBay Listings
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