Nakamichi CA-5II
A control amplifier whose MC load impedance was set at the factory to 100 ohms - and changed only by a dealer with a soldering iron and a warning about electric shock.
Overview
The CA-5II is a Nakamichi control amplifier built for the moving-coil cartridge. Its manual is blunt about what that means. Inside the unit, the load impedance for an MC-type cartridge is factory-set to 100 ohms. The plastic bags shipped with the amplifier contain five resistors each for the left and right channels so that impedance can be altered. The manual does not invite owners to do this themselves. It tells them to contact their dealer, and it warns that opening the unit carries a considerable risk of electric shock. Nakamichi would rather you drove to the shop than reached for a screwdriver.
The CA-5II was a family of units sharing one nameplate. The owner's manual covers the CA-5II, the CA-5AII, the CA-5EII, and the CA-50II, with separate chassis assemblies, front panels, and carton boxes for each. CA-5II is for "Other," Australia, and Saudi Arabia. CA-5AII is for the U.S.A. and Canada. CA-5EII is for Europe, Germany, Switzerland, and the UK. CA-50II is for Japan. The parts lists show how regional a hi-fi product could be. Even the power switch printed circuit board has four different part numbers depending on where the unit shipped, and the CA-5II (Other) version carries a voltage selector on the rear panel that toggles between 120 V and 220-240 V.
Know how the CA-5II differs from its siblings before buying one. The load-impedance resistor kit is documented for the CA-5EI, CA-5AI, and CA-5I variants, and the supplement sheet for that kit is listed specifically for the CA-5II (Australia) and CA-5AII (U.S.A.). Buyers chasing a particular regional build should read the back panel and the serial number, not the badge on the front. The manual's serial number break is given as B10801001 onward.
Period coverage of the CA-5II is thin in the archive. HiFI-Stereo (February 1989, p.89) listed a Nakamichi control amplifier in its amplifiers roundup alongside a Parasound unit. The Nakamichi entry carried a price of $530 and a claimed total harmonic distortion of 0.005%. The same listing notes a phono signal-to-noise ratio of 85 dB and an RIAA response accuracy of ±0.3. On paper the CA-5II was built to compete at the top of the mid-market rather than to undercut it.
Treat the CA-5II as a specialist tool rather than a general-purpose preamp. The MC load impedance is not switchable from the front panel. It is a factory setting of 100 ohms, and changing it takes a dealer visit and a resistor swap. That design suggests Nakamichi expected a buyer with one good moving-coil cartridge, one good dealer, and no interest in fiddling.
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