Kenwood-Trio KA-3500 Amplifier Review

This is a simple amplifier with the minimum of facilities and inputs but giving adequate power for normal domestic applications, being rated at 40W per channel into 8 ohms or 45W into 4 ohms. However the available power into 2 ohms was well down on the 4 ohms performance, with the result that the use of 4 ohm loudspeakers requires some caution in selecting units which do not exhibit a low impedance.

Very sensibly the two sets of loudspeakers’ outputs have been arranged to put the sets of loudspeakers in series when both sets are selected, so at least the Kenwood-Trio KA-3500 never looks into a nominal impedance of less than 4 ohms. In addition to the loudspeaker outputs, there is a headphone jack and the loudspeaker selector switch has an ‘off’ position for headphone listening.

Whilst the volume control gave a good performance when listening on loudspeakers, the use of headphones meant that the volume control was always near its minimum setting, and the volume steps were far too large for comfort. However, output noise was low and did not present any problem as neither did the input noise from any of the sources, with the pick-up input being very good.

The input impedance and sensitivity of the high level auxiliary and tuner inputs was satisfactory, but that of the magnetic cartridge input was a little on the high side at 58k ohms.

In addition to these three inputs which are pushbutton selected, there is provision for two tape units via rear panel phono sockets and a single DIN compatible socket associated with one tape unit. Control of the tape functions is by means of two three-position toggle switches, one of which provides tape dubbing in either direction and the other of which selected either tape unit for tape monitoring, the crosstalk associated with this switch and with the source selector pushbuttons being mediocre.

Only one filter is provided, being a low pass filter of sensible performance, but we would like to have seen some roll-off in the low frequency response at the phono input, as amplifiers in this price range are likely to be used with cheaper turntables which need the use of a rumble filter.

An unusual and rather impractical feature of the filter is that it is selected by a three position toggle switch, the third position of which is used for the loudness control. As the loudness control therefore cannot be used in conjunction with the filter, this seems to be a peculiar idea.

The treble and the bass tone controls are of the types which use a potentiometer with a detent mechanism which really doesn’t achieve anything very useful. Furthermore, with the Kenwood-Trio KA-3500 the tone controls did little around their centre positions and were far too sensitive in their increments at the extreme positions, but it must be added that the overall tone control range was restricted to a sensible ±9dB.

The final control is the balance control which is a potentiometer with a central click stop. It was very smooth in action whilst allowing either loudspeaker to be cut off.

Measurements show that the low power distortion is to a high standard, but there are reservations about the half power intermodulation performance and the wide variation between the power bandwidth of the two channels, in addition to which the amplifier did not like high power transients.

The standard of construction was generally good with clean board layouts and widespread use of wire wrapping which is more reliable than soldering.

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