Yamaha CA-610 Amplifier Review
The control arrangements of the Yamaha CA-610 amplifier are unusual because a single rotary switch is used to select all inputs including tape monitoring, the basic inputs being a magnetic phono cartridge input, tuner and auxiliary inputs, plus two tape units.
Input signals to the tape units are selected by a further rotary switch which feeds the tape units from the phono, auxiliary or tuner sources and also allows tape dubbing in either direction. All input impedances and levels are sensible as are overload margins, and in addition to the phono sockets used for the signal inputs the tape units can also be fed from DIN compatible connections.
Clip type connectors are fitted for two sets of loudspeakers which are selected individually or as pairs in parallel by the front panel speakers switch which also has an ‘off’ position for use when listening with headphones via the front panel headphone jack socket. Examination of the power output capability of the amplifier shows that it delivers a good power into either 4 or 8 ohms, but that 2 ohm loads provoke disaster. It is therefore suggested that some care is required in selecting suitable 4 ohm loudspeakers, or for that matter when running two sets of 8 ohm loudspeakers simultaneously because some of these which have a nominal impedance of 8 ohms can halve their nominal impedance at discrete frequencies.
Both harmonic and intermodulation distortion were at very low levels within the audio frequency band, and intermodulation distortion at high frequencies was also very respectable. Similarly the noise performance of all the inputs was to a high standard providing a good dynamic range. However the worst volume setting noise which occurs at 10 o’clock on the volume control may be troublesome when listening with headphones.
In other respects the performance of the volume control and its 21dB ‘muting’ switch were very good, and neither these or any other controls introduced significant unbalance between the amplifier channels. The balance control itself was also good with a fine control area around its mid position which had a useful mechanical click stop.
The treble and the bass tone controls are of the potentiometer type, each having an associated ‘defeat’ toggle switch â€" two switches seem a bit unnecessary. Subjectively the tone control had a very wide range, but as they are pure potentiometer types this didn’t matter as their control law was satisfactory and permitted fine adjustment.
The amplifier is fitted with a single high pass filter which has been well conceived with its â€"3dB point at 25Hz and a rapid roll off at 12dB per octave, in addition to which the amplifier has been rolled off with a similar rate of attenuation below 7Hz, but unfortunately the high frequency response has not been similarly controlled and extends unnecessarily to above 200kHz.
The remaining features of the Yamaha CA-610 are the switched loudness control which gives a substantial boost to both the treble and the bass, and two meters which are scaled in Watts into 8 ohms. As is common with so many amplifiers which have meters these are far too slow to indicate peak overload conditions, to the extent that they indicated only 1W under transient overload conditions.
Both bass and treble overload was subjectively smooth, and other than a parasitic oscillation at 1.6mHz in one sample of the amplifier, no troubles were encountered. The standard of construction was generally good with a reasonable standard of wiring, but component identifications were mediocre and the mains cable clamp loose.