Review

Yamaha CA-810 Amplifier Review

To start with, the Yamaha CA-810 amplifier has one feature which comes as a surprise; the two front panel level meters, which are calibrated in decibels above and below maximum output and in watts into 8 ohms, are actually useful. Unlike other amplifiers the meters had a fast rise time, and really did indicate peak levels and the onset of distortion.

A headphone jack socket and two sets of loudspeakers connections are provided, with switch selection of ‘off’ and either or both sets of loudspeakers in parallel. However caution is required in the selection of suitable loudspeakers, as the amplifier does not take kindly to 2 ohm loads with the result that audible distortion occurred when using two loudspeakers of nominal 8 ohm impedance in parallel, particularly when loudspeakers of a nasty impedance characteristic were used.

In other respects the power capabilities of the Yamaha CA-810 were really excellent, with minimal harmonic and intermodulation distortion and a very wide power bandwidth, the intermodulation distortion above the audio frequency band being incredibly good.

The noise associated with all the inputs was to a high standard, the magnetic phono cartridge input being unusually good, and whilst the measured output noise at the worst case volume setting looks poor, in practice the use of the attenuator associated with the volume control gave an extremely good output noise performance.

Input source selection is by two rotary switches, one of which selects the auxiliary, tuner or one of the two tape inputs plus the second switch which selects a choice of three phono cartridge inputs. Two of these are for magnetic pick-up cartridges, and the third for a moving coil cartridge with a sensitivity of 60pV and good noise performance. A slightly odd arrangement is that this selector switch also selects a choice of three input impedances for the ‘phono 1’ input, measured as 98/67/49k ohms, and it is felt that this function would have been better separated from the selector switch.

The source to be recorded onto tape is selected by a further rotary switch which allows a choice, dubbing in either direction between tape units and also the selection of the tuner, auxiliary or any pick-up input. No DIN connections are fitted to this amplifier, but in addition to the inputs there is available the interface between the pre-amplifier and the power amplifier for the connection of equalizers or decoders etc.

In addition to the amplifier’s frequency response being normally rolled off at low frequencies, a high pass filter of good design is fitted in addition to the low pass filter which has its "3dB point at 10kHz with an attenuation rate of 12dB per octave. The subjective effect of this filter suggested that its frequency is set on the high side to be effective as a scratch filter or for reducing tape noise.

The treble and bass tone controls both have a choice of two turnover frequencies, the controls themselves being of the eleven position type and offering a fine correction in view of the sensible limited range.

Finally there is a variable loudness control which acts as an attenuator at the same time as altering the frequency response and of course the volume control which is concentric with a good balance control.

Subjective testing of the Yamaha CA-810 amplifier gave pleasing results with 8 ohm loudspeakers, and crosstalk between inputs etc. was to a very high standard, but this amplifier is not recommended with 4 ohm loudspeakers if they have awkward impedance characteristics.

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