Yamaha CA-800 (1976–78)

Name: Yamaha CA-800
Brand: Yamaha

Forty-five watts that flip to ten in Class A. The amp carried Yamaha's CA-1000 thinking into a ¥85,000 chassis.

Overview

Forty-five watts per channel into 8 ohms doesn't look like much on a spec sheet in 2026, but the CA-800 was never really about that number. Flip the Class A/B switch and the same amplifier drops to 10W + 10W in pure Class A, both channels driven, 20 Hz to 20 kHz. Total harmonic distortion falls to 0.02% or less at one watt. That switch is the whole point of the machine. Yamaha built the CA-800 as a stereo pre-main amplifier that inherited technology from the CA-1000, and the Class A mode is the clearest sign of that lineage: the same trickle-down philosophy, at roughly half the money.

The wattage figures get more interesting the harder you look. In Class B, the CA-800 is rated at 45W + 45W into 8 ohms across the full audio band, rising to 50W + 50W into 4 ohms. Drop to a single channel at 1 kHz and it will do 55W into 8 ohms or 70W into 4. Yamaha's own IHF dynamic power rating for Class B is 130W into 8 ohms, which tells you the power supply has more in reserve than the continuous rating suggests. The power bandwidth runs 5 Hz to 100 kHz in Class A and 5 Hz to 70 kHz in Class B, both channels driven.

Dating the CA-800 is messier than it should be. Yamaha's own literature places it in the 1976-78 window, but at least one database lists a ¥85,000 price "around 1973," and another retailer dates the model "from 1975." The archive can't reconcile those, so treat the production window as roughly the mid-to-late 1970s and the ¥85,000 figure as the price when it was new. The year on the h1 reflects the most commonly cited range, not a settled fact.

The CA-800 does have a fully documented internal architecture, which is unusual for a mid-line integrated. The main amplifier uses a pure complementary SEPP-OCL circuit with all stages directly connected to the first-stage differential amplifier. There is no interstage capacitor in the signal path. The power supply is built around a large-core transformer chosen for low voltage fluctuation even in Class B, a 6,800 µF × 2 capacitor bank, and a separate constant-voltage supply feeding every stage except the output. The equalizer section is a four-stage direct-coupled NFB design using low-noise transistors, running from a +50V regulated rail with an emitter-follower output stage. Yamaha's documentation notes that computer-aided circuit analysis was used in the design. That reads as marketing in 1976, but it shows up in the measured stability.

Contemporary coverage of the Yamaha amplifier line in Studio-Sound (May 1977, p.77) laid out the lineup's specifications in detail. The CA-800 sat well below that halo product, but the shared design language is obvious: the same regulated supplies, the same preference for discrete circuitry over op-amps, and the same Class A/B switching concept that defined Yamaha's approach to amplification in this period.

Key Features

Class A / Class B Switching at Constant Volume

The CA-800's headline feature is a front-panel switch that moves the output stage between Class A and Class B operation without changing the volume setting. Yamaha's design brief was explicit: the switch should be usable as a listening tool, not just a technical curiosity. In Class A, the amplifier idles hot and delivers 10W + 10W into 8 ohms with 0.02% or less THD at one watt. In Class B, it opens up to 45W + 45W into 8 ohms with 0.04% or less THD at one watt. The cross-modulation distortion figures follow the same pattern: 0.05% or less at one watt in either mode, 0.1% or less at rated output. A large heat sink and a two-stage protection circuit keep the output transistors and speakers safe when the amp is running in its hot mode.

Phono Stage with Three-Position Impedance Selector

The equalizer amplifier is a four-stage direct-coupled NFB design, and Phono 1 carries an input impedance selector switch with three settings: 30k, 50k, and 100k ohms. That's handy for anyone running multiple cartridges. Sensitivity is 3mV for both phono inputs. Signal-to-noise is 80dB for phono and 70dB for the mic input, rising to 90dB for tuner, AUX, and tape playback. The IHF A-weighted figure for the line inputs is 100dB. Maximum allowable phono input before distortion is 310 mVrms.

Yamaha Mixing NF Tone Control with 11-Detent Tracking

The tone controls use Yamaha's mixing NF and CR topology, built around a three-stage connected amplifier. Bass offers ±10dB at 50 Hz with selectable turnover at 250 Hz or 500 Hz. Treble offers ±10dB at 10 kHz with turnover at 2.5 kHz or 5 kHz. The front-panel knobs have 11 detents, so settings are repeatable. In boost mode the circuit lowers emitter impedance and reduces NF. In cut mode it attenuates via CR. According to Yamaha's documentation, response is flat at the knob's midpoint with no ripple. A tone defeat switch bypasses the whole section, turning it into a flat amplifier.

Continuous Loudness with Dedicated Volume

Instead of a simple on/off loudness button, the CA-800 uses a continuous loudness circuit with its own dedicated volume control. That lets the listener dial in compensation for speaker efficiency, room size, and listening level independently of the main volume. Modern amplifiers rarely keep this feature.

Pre-Main Coupler and Filter Section

The preamplifier and main amplifier sections can be separated via a rear-panel coupler, so the CA-800 can serve as a standalone preamp or a standalone power amp. A low filter offers 20 Hz or 70 Hz cutoff at 12dB/octave. A high filter offers 6 kHz or 12 kHz at 6dB/octave. An audio muting switch drops the output by 20dB. The speaker protection circuit doubles as power-on muting to suppress the thump when the amp is switched on.

Inputs, Outputs, and Rear-Panel Hardware

The rear panel carries a mic input on a 4PD-type phone jack, speaker connections via 4PD push terminals, a chassis ground terminal, and an AC socket. Two switched and two unswitched AC outlets are provided, each rated for 200W maximum. Input sensitivity is 2.5mV for mic, 3mV for MM phono, and 120mV for line-level sources. Line input impedance is 40k ohms. Pre-out is 775mV into 2k ohms. Record outputs are 120mV into 2k ohms. Headphone output accepts 4 to 16 ohm loads.

Collectibility & Value

The CA-800 sits in an odd spot in the Yamaha hierarchy. It isn't the CA-1000, which collectors chase for its place in the Class A story, and it isn't the CA-600, which sits below it. It does share a platform with the CA-600 and the CR-400. Yamaha's own parts documentation lists switch aprons, knobs, and circuit boards as common across those models, so some spares are easier to find than they would be for a one-off design.

Market prices have crept up. A listing showed €500 as of August 27, 2026. A Russian Avito listing offered one at 25,000 rubles, described as working but needing preventive maintenance. An eBay UK listing showed a partial price of 14.5 in unclear currency. One example was advertised as "serviced fully recapped," and on a 45-year-old amplifier that phrase counts for more than any cosmetic description. The CA-800 II, a related but distinct model, also turns up in listings, so buyers should confirm which version they're looking at.

The service situation is better than average. A free service manual PDF circulates online, and at least one well-viewed repair and restoration video specifically covers the CA-800 alongside the CA-1000, which means the common failure points are documented by people who have actually opened the chassis. The most common condition note in listings is that a unit "needs preventive maintenance" — which on an amp of this age usually means capacitors, switches, and a bias check. The parts documentation is unusually complete for a mid-line model, down to individual switch aprons and knob part numbers, which is the kind of thing that separates a unit you can still service in 2026 from one you cannot.

One caveat: a negative review on the Vintage Asylum forum criticizes Yamaha's DTS AV receivers, not the CA-800 or any component from this era. That complaint has no bearing on a 1970s two-channel integrated.